# HISTORICAL METEOROLOGICAL ANALYSIS IN SUPPORT OF THE 2003 SAN JOAQUIN VALLEY PM 10 

# STATE IMPLEMENTATION PLAN

FINAL REPORT



# Prepared By:
Shawn R. Ferreria Air Quality Meteorologist / Atmospheric Scientist
and Evan M. Shipp Supervising Air Quality Meteorologist San Joaquin Valley Air Pollution Control District

January 24, 2005

### ii ACKNOWLEDGEMENTS

We wish to acknowledge the contributions of Air Resources Board Staff, Ms. Karen Magliano, Ms. Kasia Turkiewicz, and Mr. Rich Hackney who provided valuable information in the compiling and reviewing of this document. We wish to also acknowledge the contribution of the members of the PM 10 

### Modeling group who provided extremely useful discussions during the planning, intermediate stages, and development of this document.

### iii TABLE OF CONTENTS

Section Page

ACKNOWLEDGEMENTS..................................................................... ii
LIST OF FIGURES..............................................................................v
LIST OF TABLES............................................................................... vi
EXECUTIVE SUMMARY..................................................................... vii

1.0 NOVEMBER 6, 1997 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION............................................................................1

2.0 DECEMBER 31, 1998 AND JANUARY 12, 1999 EPISODE
SYNOPTIC METEOROLOGICAL DISCUSSION...............................4

3.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND METEOROLOGY DURING THE JANUARY 12, 1999 EPISODE.........10

4.0 OCTOBER 21, 1999 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION...........................................................................15

5.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND METEOROLOGY DURING THE OCTOBER 21, 1999 EPISODE .......18

6.0 NOVEMBER 14, 1999 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION.......................................................................... 22

7.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND METEOROLOGY DURING THE NOVEMBER 14, 1999 EPISODE......26

8.0 DECEMBER 17 AND 23, 1999 EPISODE SYNOPTIC
METEOROLOGICAL DISCUSSION.................................................29

9.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND
METEOROLOGY DURING THE DECEMBER 1999 EPISODE............35

10.0 DECEMBER 1999 AND JANUARY 2000 PM 2.5 

### & PM 10 

### METEOROLOGICAL DISCUSSION..............................................40

11.0 DECEMBER 2000 AND JANUARY 2001 EPISODE SYNOPTIC
METEOROLOGICAL DISCUSSION.................................................51

12.0 DISPERSION METEOROLOGY FOR THE FALL 2000 AND WINTER 2001 CRPAQS..........................................................................58

### iv 13.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND
METEOROLOGY DURING THE JANUARY 2001 EPISODE...............69

14.0 NOVEMBER 9, 2001 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION...........................................................................77

15.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND METEOROLOGY DURING THE NOVEMBER 9, 2001 EPISODE.......81

16.0 MAY 19 AND 20, 2002 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION...........................................................................84

17.0 REFERENCES.........................................................................90

### v LIST OF FIGURES

1 Corcoran PM 10 

### , Fresno Precipitation, and T850 Stability Fall 1997.............1 2 Atmospheric Temperature Profile at Fresno on November 06, 1997...........2 3 T850 Stability and Precipitation vs. PM 10 

### at Bakersfield (12/98-01/99).........4 4 Atmospheric Temperature Profile at Bakersfield on 12/31/1998.................6 5 Atmospheric Temperature Profile at Bakersfield on 01/12/1999.................8 6 Bakersfield-Golden(Coarse, PM 10 

### & 2.5 

### ) 12/1998 & 01/1999.....................11
7 Visalia and Oildale PM 10 

### December 1998 & January 1999......................11
8 Fresno-1 st 

### PM 10 

### & 2.5 

### , Precipitation, T850 Stability and Model PM 10 

### 10/99...16 9 Atmospheric Temperature Profile at Fresno on October 21, 1999.............17 10 October 1999 Solar Intensity.............................................................17 11 Corcoran (Coarse, PM 10 

### & 2.5 

### ) and Fresno-1 st 

### (PM 2.5 

### ) 10/21/1999..............18
12 Turlock-Minaret and Fresno-Drum. PM 10 

### and Fresno-1 st 

### (PM 2.5 

### ) 10/21/99...19 13 T850 Stability & Precipitation vs. PM10 &2.5 at Bakersfield-Gold F/W99....22 14 Atmospheric Temperature Profile at Bakersfield on 11/14/99...................24 15 Bakersfield Golden (PM 2.5 

### &Coarse) and Fresno-1 st 

### (PM 2.5 

### ) 11/14/99........26 16 Bakersfield Calif. (Coarse, PM 2.5 

### & 10 

### ) and Fresno-1 st 

### (PM 2.5 

### ) 11/14/99.......27 17 T850 Stability & Precipitation at Hanford vs. PM 10 

### & 2.5 

### at Corcoran 12/99....29 18 Atmospheric Temperature Profile at Fresno on December 17, 1999...........31 19 T850 Stability and Precipitation vs. PM 10 

### & 2.5 

### at Hanford, Dec. 1999...........33 20 Atmospheric Temperature Profile at Fresno on December 23, 1999...........34 21 Corcoran (Coarse, PM 2.5 

### & 10 

### ) and Fresno-1 st 

### (PM 2.5 

### ) 12/17/99..................35 22 Fresno Drummond (PM 10 

### ) and Fresno 1 st 

### (PM 2.5 

### ) 12/17/99.......................36 23 Hanford (PM 10 

### ) and Fresno 1 st 

### (PM 2.5 

### ) 12/23/99.....................................38 24 T850 Stability vs. PM 10 

### and PM 2.5 

### at Corcoran for 12/99 and 01/00............40
25 PM 2.5 

### at Fresno 1 st 

### and Bakersfield California for 12/99 and 01/00.............42 26 Atmospheric Temperature Profile at Fresno on Dec. 17, 1999..................43 27 T850 Stability and Precipitation vs. PM 10 

### at Hanford 12/99.......................46 28 Atmospheric Temperature Profile at Fresno on Dec. 23, 1999..................46 29 Wind Rose at Clovis Air Monitoring for 12/17 & 12/23/99, & 01/07/2000......49
30 Fresno-1 st 

### Stability and Pollutant Trends for Fall 2000 & Winter 2001.........52
31 Fresno-1 st 

### Fall 2000 and Winter 2001 Episode.......................................59
32 Fresno-1 st 

### (Coarse) & (PM 2.5 

### ) January 2001 Episode..............................65 33 Bakersfield California (Coarse) &(PM 2.5 

### ) January 2001 Episode.................65 34 Bakersfield Golden (Coarse, PM 10 

### & 2.5 

### ) &Baker. Cal. (PM 2.5 

### ) ’01 Episode.....65 35 Hanford, Oildale, & Modesto (PM 10 

### ) & Fresno-1 st 

### &Baker. Cal. (PM 2.5 

### ).........66
36 Fresno-1 st 

### (Coarse) and (PM 2.5 

### ) January 2001 Episode............................70 37 Bakersfield California (Coarse) and (PM 2.5 

### ) January 2001 Episode..............72 38 Bakersfield Golden (Coarse, PM 10 

### & 2.5 

### ) &Baker. Cal. (PM 2.5 

### ) ’01 Episode.....72 39 Hanford, Oildale, & Modesto (PM 10 

### ) & Fresno-1 st 

### &Baker. Cal. (PM 2.5 

### ) January 2001 Episode........................................................................72 40 T850 Stability & Precipitation vs. PM 10 

### at Hanford, Fall & Winter 2001..........77 41 Atmospheric Temperature Profile at Fresno on November 9, 2001..............79 42 Hanford (PM 10 

### ) and Fresno 1 st 

### (PM 2.5 

### ), November 9, 2001.........................81 43 Corcoran (PM 2.5 

### &Coarse) and Fresno-1 st 

### (PM 2.5 

### ), November 9, 2001...........82

### vi LIST OF FIGURES (continued) 44 Visalia Lower Air Profiler Image for May 19 – May 20, 2002....................86 45 Lost Hills Lower Air Profiler Image for May 19 – May 20, 2002.................86 46 Hourly Ave. Wind Speeds at Bakersfield Golden on 5/19 – 5/20, 2002......89

LIST OF TABLES

1 Federal Reference Method (FRM) Daily Ave. PM Measurements, 11/6/97.... 1 2 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 11/6/97..... 3 3 FRM Daily Ave. PM Measurements for sites across SJV for 12/31/1998....... 5 4 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 12/31/98... 6 5 FRM Daily Ave. PM Measurements for sites across SJV for 01/12/1999....... 7 6 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, &CIMIS sites for 1/12/99......8 7 FRM Daily Ave. PM Measurements for sites across the SJV for 11/14/99....23 8 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 11/14/99...25 9 FRM Daily Ave. PM Measurements for sites across the SJV for 12/17/99.....30 10 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 12/17/99...31 11 FRM Daily Ave. PM Measurements for sites across the SJV for 12/23/99.....32 12 CRPAQS Daily Ave. PM Meas. for Fresno-Dru. & Hanford for 12/23/99.......32 13 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 12/23/99...34 14 FRM Daily Ave. PM Measurements for sites across the SJV for 12/17/99.....42 15 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS,& CIMIS sites for 12/17/99....44 16 FRM Daily Ave. PM Measurements for sites across the SJV for 12/23/99.....45. 17 CRPAQS Daily Ave. PM Meas. for Fresno-Dru. & Hanford for 12/23/99.......45 18 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 12/23/99...47 19 CRPAQS Episode Event Summary Table at Fresno................................53
20 PM 10 

### Chemical Composition Data for Jan. 1, 4, &7 2001 at selected sites.....64
21 PM 10 

### Chemical Composition Data for Jan. 1, 4, & 7 2001 at selected sites....71 22 FRM Daily Ave. PM Measurements for sites across the SJV for 11/9/2001....78 23 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, &CIMIS sites for 11/9/2001....79 24 Peak & Daily Ave. PM Measurements for sites across the SJV for 5/19/2002..84 25 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 5/19/2002...85 26 Peak & Daily Ave. PM Measurements for sites across the SJV for 5/20/2002..87 27 24 hr. Ave. Wind Speeds at SJVAPCD, ASOS, & CIMIS sites for 5/20/2002...88

### vii 

## EXECUTIVE SUMMARY

Study Purpose

This document characterizes meteorology and air quality experienced during the Particulate Matter (PM) season from November 1997 through May 2002. The evaluation was focused on understanding the causes of particulate matter concentrations that exceeded the National Ambient Air Quality Standards (NAAQS) in the San Joaquin Valley by exploring the meteorology and chemistry of each episode. Utilizing daily
PM 2.5 

### and PM 10 

### concentrations, chemical composition, and meteorological data, each
PM 10 

### episode was identified. An episode was defined as the complete period, from the beginning through the end, where PM 10 

### concentrations increased to a peak that

exceeded the Federal PM 10 

### Standard of 150 μ g/m 3 

### and then decreased dramatically as atmospheric dispersion conditions improved. This analysis was a collaborative effort with contributions from the Air Resources Board staff, including Ms. Karen Magliano, Ms. Kasia Turkiewicz, and Mr. Rich Hackney and also members of the PM 10 

### modeling group. The general objectives of the characterization analyses are to provide:

1. Support for the 2003 San Joaquin Valley PM State Implementation Plan (SIP) and other District programs 2. Development and improvement of the conceptual model 3. An understanding of San Joaquin Valley meteorology and how it influences particulate formation and accumulation.

Summary of Findings

During each episode, cooler air at the surface and warm air above the mixing layer trapped pollutants under a strong temperature inversion. Horizontal movement of air was minimal and disorganized reducing dispersion and transport of pollutants. These conditions caused particulates to increase throughout the San Joaquin Valley. Under the poor mixing conditions, coarse and fine particulates accumulated leading to high particulate concentrations.

A majority of the episodes were characterized by a prolonged period (two to three weeks) of limited mixing and light wind flow. The November 14, 1999 and November 9, 2001 were an exception, when strong stability and local emissions drove concentrations
at the PM 10 

### monitoring sites over the NAAQS in less than a week and a half. Winter exceedances (December and January) were characterized by an increase in fine particles to a level that dominated filter samples. Fall exceedances (October and November) were dominated by coarse particles. To a lesser extent in the fall and a greater extent in the winter, cool damp mornings and restricted vertical air movement
contributed to the formation of nitrates and sulfates. Total carbon concentrations from combustion sources remained proportionally the same during the fall and winter exceedances. Due to stagnant weather conditions, the elevated PM 10 

### and PM 2.5 

### measurements that resulted in an exceedance of the NAAQS were caused primarily by

### viii local emission sources, rather than background or long-range transport of material in most of the episodes. An analysis of a wind blow dust event that occurred on May 19 and 20, 2002 was also done.

As stated above during most episodes winds and transport were minimal. However, during the CRPAQS 2001 episode given the length of the episode and the large contributions from secondary components, there was an underlying regional component to this episode as it progressed. Local carbon and geologic contributions added to this regional component and influenced site to site concentration variations. As the CRPAQS episode continued, PM and precursors became more homogeneous across the region. This resulted in PM 2.5 

### concentrations at rural sites lagging those of urban sites, and rural concentrations continued to build throughout the episode.

The October 1999 particulate episode was unique and did not follow the general meteorological and chemical pattern observed in other episodes. Concentrations during this event were dominated by geological particles (PM 10 

### ), with significant contributions from fine particulates of ammonium nitrate and sulfate and total carbon. The abundance of fine particulates in the samples may have been due to abnormalities in atmospheric chemistry reactions. Due to several wildfires to the north and a major tire fire at Westley earlier in October, particulate loading aloft may have decreased solar radiation intensity measurements across the Valley Floor. With reduced solar radiation, the atmospheric chemistry reactions may have changed from the ozone forming regime of mid-October to the secondary particulate regime of late November. Although geological particulates dominated the samples, fine fractions of PM were elevated. Limited afternoon heating and stagnant weather conditions, resulted in local sources driving PM 10 

### concentrations to exceed the NAAQS.

With these similarities and differences among the episodes, each PM 10 

### episode is discussed in detail in the following sections. PM 10 

### and PM 2.5 

### concentrations, chemical composition, and meteorological data around the exceedance dates are evaluated and analyzed to identify the characteristics and uniqueness of the exceedances at the FRM and CRPAQS PM 10 

### and PM 2.5 

### monitoring sites.

### 1 

## 1.0 NOVEMBER 06, 1997 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION

October 11 – November 7, 1997

After a cold front and trough passage on October 11 th 

### , high pressure from the eastern Pacific built into the region, with increasing stability and poor dispersion conditions through the exceedance date on November 6 th



### , Figure 1. At Corcoran, Patterson Ave.,

a 24-hour PM 10 

### (Particulate Matter) concentration of 199 μ g/m 3 

### was measured. Table 1 outlines federal reference method (FRM) Daily Average Particulate Matter Measurements for sites across the San Joaquin Valley (SJV). In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.

Figure 1: Corcoran PM10, Fresno Precipitation, and T850 Stability

Fall 1997

0 25 50 75 100 125 150 175 20010/1/199710/3/199710/5/199710/7/199710/9/199710/11/199710/13/199710/15/199710/17/199710/19/199710/21/199710/23/199710/25/199710/27/199710/29/199710/31/199711/2/199711/4/199711/6/199711/8/199711/10/199711/12/199711/14/199711/16/199711/18/199711/20/199711/22/199711/24/199711/26/199711/28/199711/30/1997PM10 (micrograms/meter^3) and Precipitation/100(inches)

-20 -15 -10 -5 0 5 10 15T850 Stability Parameter (C) Corcoran PM10

Fresno PPT/100

FAT T850 Stability



### TABLE 1: Federal Reference Method (FRM) Daily Average Particulate Matter Measurements for sites across the SJV for November 06, 1997.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.
Corcoran * 199 Visalia 83 Bakersfield-CA 95
Corcoran # 154 Turlock 56 Bakersfield-Gold 124
Clovis 83 Modesto 44 Hanford 143
Fresno-1st 92 Taft 42 Oildale 125

* -Patterson # -Van Dorsten

units in μ g/m 3

### 2 The meteorological synoptic analysis showed after an extended period of strong high pressure and surface and upper air stability from October 11 th 

### through November 5 th



### , leading to building PM conditions, a trough developed across the eastern Pacific, the morning of the 6 th 

### . The trough and accompanying weak cold front slowly moved southeastward across California during the late afternoon hours. The morning surface charts depicted a surface high pressure ridge draped across Central California from the Four Corners Region to San Francisco. The 12Z surface pressure gradient was –0.6 millibars from San Francisco (SFO) to Las Vegas (LAS). A –0.6 millibars pressure gradient means light offshore flow, which results in weak disorganized wind flow across the San Joaquin Valley.

The morning temperature sounding over Fresno showed a strong inversion (stable layer) of 19 degrees Fahrenheit from the surface up to 1,500 feet as is evident in Figure
2. At Bakersfield the temperature sounding showed a similar strong inversion of 17 degrees Fahrenheit from the surface up to 1,500 feet. The temperature soundings on
the 6 th 

### , are conducive of elevated PM levels due to low mixing depths, which keep pollutants trapped near the surface.

Figure 2: Atmospheric Temperature Profile at Fresno on November 06, 1997

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

50 55 60 65 70 75 80

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a moderate low near Vancouver Island, with a weak trough curving south-southeastward across the eastern Pacific and along the West Coast. A moderate temperature gradient at 850 MB and an upper level jet were evident over central California. Weak pressure gradients across the San Joaquin Valley strengthened slightly during the afternoon hours, with the approach of the cold front.
Table 2 shows the 24 hour daily average wind speeds at SJVAPCD air monitoring, ASOS, and CIMIS sites for November 06, 1997.

### 3 Table 2: 24 hour average wind speeds at SJVAPCD air monitoring, ASOS, and CIMIS sites for November 06, 1997.

SJVAPCD Air Monitor ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 4.8 FAT 6.8 Shafter/USDA 3.8 Famoso 3.6 Fresno Sierra Sky Park (SSP) 3.3 Firebaugh/Telles 4.6 Westlands 4.5

Corcoran 6.8 Stratford 5 Panoche 4

Kettleman 3.8 Arvin-Edison 3.2

Visalia/Americas 3.1 Lindcove 2.1

Parlier 4.3 Kesterson 3.1

Blackwells Corner 3.7 Lodi West 2.9

Los Banos 4.5 Modesto 3.6

Manteca 2.8 Fresno State 5.1



### Due to strong stability lasting for over 28 days, PM 10 

### steadily increase region-wide until
November 6 th 

### . Light disorganized wind flow, a strong morning inversion and pre-frontal stability; lead to limited dispersion conditions on the 6 th 

### causing local PM emissions in Corcoran to rapidly increase past the Federal 24-hour PM 10 

### standard to 199 μ g/m 3



### . Since other FRM Monitoring sites did not register above the Federal 24-hour PM 10 

### standard on the 6 th 

### , the Corcoran PM 10 

### measurement signifies local emission characteristics. Crop calendar activity shows that cotton/safflower and alfalfa were being prepared and harvested during early November. A weak frontal boundary moved through the region on the 7 th 

### , bringing better dispersion conditions and lowering
Corcoran’s PM measurement to well below the standard.

### 4 

## 2.0 DECEMBER 31, 1998 AND JANUARY 12, 1999 EPISODE
SYNOPTIC METEOROLOGICAL DISCUSSION

December 20, 1998 – January 16, 1999

The period from December 20, 1998 to January 16, 1999 was marked by 28 days of strong stability and poor atmospheric dispersion conditions. Strong high pressure over the Intermountain Region and eastern Pacific dominated the period, leading to limited dispersion. The period began with the passage of a cold, arctic front and trough on the
20 th 

### . Between the 20 th 

### and the 31 st 

### , increasing stability and poor dispersion conditions
resulted in a PM 10 

### (Particulate Matter) exceedance at Bakersfield Golden and Visalia
Church on the 31 st



### , Figure 3.

Figure 3: T850 Stab ility and Precipitation vrs. PM10

at Bakersfield Golden December 1998 and Mid January 1999

0 20 40 60 80 100 120 140 16012/1/199812/3/199812/5/199812/7/199812/9/199812/11/199812/13/199812/15/199812/17/199812/19/199812/21/199812/23/199812/25/199812/27/199812/29/199812/31/19981/2/19991/4/19991/6/19991/8/19991/10/19991/12/19991/14/19991/16/19991/18/1999PM10 (micrograms/meter^3) andPrecipitation/100 (inches)

-12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0T850 Stability Parameter(C) Precipitation/100(inches)

PM10

T850 Stability(OAK)

T850 Stability(VBG)



### At Bakersfield Golden and at Visalia Church, a 24-hour PM 10 

### concentration of 159 and

160 μ g/m 3 

### were measured, respectively. Table 3 outlines federal reference method (FRM) Daily Average Particulate Matter Measurements for sites across the San Joaquin Valley (SJV). In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.

### 5 TABLE 3: Federal Reference Method (FRM) Daily Average Particulate Matter Measurements for sites across the SJV for December 31, 1998.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

Bakersfield-Gold 159 Turlock 87 Hanford 109

Bakersfield-CA 148 Modesto 80 Stockton# 99

Visalia 160 Taft 73 Stockton** 95

Fresno-1 st 

### 104 Fresno-Drum 117 Corcoran* 116

* -Patterson #-Wagner, **- Hazleton

units in μ g/m 3



### The meteorological synoptic analysis showed after a period of strong atmospheric stability from December 20 th 

### through the 31 st 

### , a weak disturbance from the eastern Pacific approached the region. Ahead of the weak trough, stability lingered over the southern parts of the San Joaquin Valley trapping particulates within the Valley boundary layer. The afternoon surface charts on the 31 st 

### depicted a surface ridge extending southeastward across southern California from a strong high 200 NM west of Eureka. A weak cold front was draped northwestward along the Sierra Nevada Mountain range from near Bishop to Reno. The 0Z surface pressure gradient was +13.0 millibars from San Francisco (SFO) to Las Vegas (LAS), with isobars(constant surface pressure) orientated northeast to southwest. With the alignment of the isobarsand the +13.0 millibars pressure gradient, this represents light to moderate northnortheasterly flow across the San Joaquin Valley. Visibilities throughout the day across the San Joaquin Valley were reporting haze.

The morning temperature aircraft sounding over Bakersfield showed multiple inversions, with a moderately strong inversion (stable layer) of 10 degrees Fahrenheit from the surface up to 2,000 feet, with a secondary inversion of 4 degrees Fahrenheit from 2,500 to 4,500 feet as is evident in Figure 4. The temperature sounding on the 31 st 

### , is conducive of elevated PM levels due to low mixing depths and multiple inversions, which keep pollutants trapped near the surface. At surface observations across the San Joaquin Valley, minimum temperature at Fresno was 38 degrees Fahrenheit and Bakersfield was 37 degrees Fahrenheit. These cold and poor dispersion conditions generally result in elevated concentrations of ammonia nitrate. Also on New Year’s Eve (December 31), there is a great amount of residential wood combustion in the area.

### 6 Figure 4: Atmospheric Temperature Profile at Bakersfield on December 31, 1998

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

40 45 50 55 60

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a strong high 600 NM west of Santa Barbara, with a ridge building northward into the eastern Gulf of Alaska. A weak trough over the Intermountain region extended southwestward across northern California. Weak pressure gradients across the San Joaquin Valley strengthened during the afternoon hours, with the approach of the cold front.

Table 4 shows the 24 hour daily average wind speeds at SJVAPCD monitoring sites, ASOS, and CIMIS sites for December 31, 1998.

SJVAPCD Monitoring Sites ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 5.5 Fresno 6.5 Shafter/USDA 3.0 Famoso 3.2

Fresno SSP 3.0 Bakersfield 4.0 Firebaugh/Telles 5.4 Westlands 6.5

Corcoran 4.7 Hanford 4.7 Stratford 3.8 Panoche 5.6

Edison 4.3 Kettleman 3.6 Arvin-Edison 3.0

Parlier 5.3 Visalia/Americas 2.8 Lindcove 2.1

Arvin 3.6 Parlier 4.2 Kesterson 5.0

Visalia 1.8 Blackwells Corner 3.3 Lodi West 3.9

Los Banos 6.3 Modesto 5.6

Manteca 4.9 Fresno State 5.2



### Due to the strong stability lasting for over 11 days, PM 10 

### steadily increase region-wide
until December 31 st 

### . With the approach of the weak upper level trough from northern California, moderately strong stability lingered over the southern parts of the San Joaquin Valley. This resulted in local PM 10 

### concentrations at Bakersfield-Golden and

Visalia to increase above the Federal 24-hour PM 10 

### standard to 159 and 160 μ g/m 3



### , respectively. Due to the tightening pressure gradient in the northern part of the San Joaquin Valley and weak upper level trough passage, widespread San Joaquin Valley PM10 exceedances did not occur on this date. The weak upper level trough traversed the entire region late on the 31 st 

### bringing slightly better dispersion conditions to the entire San Joaquin Valley on January 1 st 

### , resulting in lower PM Valley-wide.

### 7 After the weak upper level trough passage on the 31st, strong high pressure rebuilt into the region from the Great Basin and eastern Pacific, with increasing stability and poor dispersion conditions through the next exceedance date on January 12 th 

### at Oildale, Figure 3 . At Oildale, a 24-hour PM 10 

### (Particulate Matter) concentration of 156 μ g/m 3



### was measured.

Table 5 outlines federal reference method (FRM) Daily Average Particulate Matter Measurements for sites across the San Joaquin Valley (SJV). In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.

TABLE 5: Federal Reference Method (FRM) Daily Average Particulate Matter measurements for sites across the SJV for January 12, 1999.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

Bakersfield-Gold 109 Turlock 53 Oildale 156

Bakersfield-CA 92 Modesto 48 Stockton# 39

Visalia 82 Taft 70 Stockton** 48

Fresno-1 st 

### 85 Fresno-Drum 76 Corcoran* 51

* -Patterson #-Wagner, **- Hazleton

units in μ g/m 3



### The meteorological synoptic analysis showed after a period of strong atmospheric stability from December 31 st 

### through the 12 th 

### , a weak upper level disturbance from the eastern Pacific approached the region. Ahead of the weak trough, mid-tropospheric stability lingered over the southern parts of the San Joaquin Valley trapping particulates within the Valley boundary layer. The morning surface charts of January 12 th 

### depicted a surface ridge extending southeastward across the central San Joaquin Valley from a strong high just west of San Francisco. The 12Z surface pressure gradient was +9.0 millibars from San Francisco (SFO) to Las Vegas (LAS), with isobars (constant surface pressure) orientated northeast to southwest. With the alignment of the isobars and the +9.0 millibars pressure gradient, this represents light to moderate north-northeasterly flow across the San Joaquin Valley. Visibilities across the San Joaquin Valley in the morning reported fog turning to haze by the afternoon.

The morning temperature aircraft sounding over Bakersfield showed multiple inversions, with a moderately strong inversion (stable layer) of 12 degrees Fahrenheit from the surface up to 1,000 feet, with a secondary inversion of 4 degrees Fahrenheit from 1,500 to 3,000 feet as is evident in Figure 5. The temperature sounding on the January 12 th



### , is conducive of elevated PM levels due to low mixing depths and multiple inversions, which trap pollutants near the surface. At surface observations across the San Joaquin

### 8 Valley, minimum temperature at Fresno was 30 degrees Fahrenheit and Bakersfield was 29 degrees Fahrenheit.

Figure 5: Atmospheric Temperature Profile at Bakersfield on January 12, 1999

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

30 35 40 45 50

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a moderate high well off of Baja, with a ridge draped northeastward across central California. A weak trough bends southward along the Pacific Northwest Coast from a low over the eastern Gulf of Alaska. Pressure gradients weakened slightly during the afternoon hours further decreasing boundary layer flow in the San Joaquin Valley.

Table 6 shows the 24 hour daily average wind speeds at SJVAPCD monitoring sites, ASOS, and CIMIS sites for January 12, 1999.

SJVAPCD Monitoring Sites ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 2.6 Fresno 1.8 Shafter/USDA 2.6 Famoso 2.7

Fresno SSP 1.5 Bakersfield 4.8 Firebaugh/Telles 2.5 Westlands 3.1

Corcoran 3.0 Hanford 1.3 Stratford 2.9 Panoche 3.1

Edison 4.0 Kettleman 3.2 Arvin-Edison 2.9

Parlier 2.9 Visalia/Americas 2.4 Lindcove 2.0

Arvin 3.3 Parlier 2.5 Kesterson 2.4

Visalia 1.4 Blackwells Corner 2.5 Lodi West 2.7

Los Banos 2.9 Modesto 4.5

Manteca 4.0 Fresno State 2.7



### Due to the strong stability lasting for over 24 days, PM 10 

### steadily increase region wide until January 12 th 

### . With the approach of the weak trough from northern California, moderately strong stability lingered over the southern parts of the San Joaquin Valley leading to local PM concentrations at Oildale increasing above the Federal 24-hour

PM 10 

### standard at 156 μ g/m 3 

### . Due to the increasing dispersion aloft from the weak upper level trough passage, widespread San Joaquin Valley PM10 exceedances did not occur on this date; thus the exceedance at Oildale was representative of local emissions driving the particulate measurement. Weak upper level disturbances

### 9 continued to traverse the region through January 16 th 

### , bringing better dispersion conditions and an end to the PM episode that recorded exceedances at Bakersfield and
Visalia on December 31 st 

### , 1998 and Oildale on January 12 th 

### , 1999.

### 10 

## 3.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND METEOROLOGY DURING THE JANUARY 12, 1999 EPISODE

The January 1999 particulate episode was characterized by a prolonged period (four weeks) of strong stability and light wind flow, which resulted in poor atmospheric dispersion conditions across the San Joaquin Valley. Coarse and fine particulates accumulated during the period, leading to two separate exceedance days on Thursday, December 31, 1998 and Tuesday, January 12, 1999. A weak upper level disturbance moved over the region on December 31, 1998, dividing the episode into two separate periods. Concentrations were dominated by the fine particulates (PM 2.5 

### ) of ammonia nitrate and sulfate and were most prevalent in the central and southern San Joaquin Valley. The first period was marked by strong stability and light wind flow, which led to
exceedances at Bakersfield-Golden with a PM 10 

### concentration of 159 μ g/m 3 

### and VisaliaChurch with a PM 10 

### concentration of 160 μ g/m 3 

### on December 31, 1998 ( Figure 6 & 7 ).
PM 10 

### concentrations at other central and southern Valley locations were much lower,

below 115 μ g/m 3 

### , with the exception of nearby Bakersfield-California, which measured a

PM 10 

### concentration of 148 μ g/m 3 

### . However, the December 1998 exceedances are included in the discussion to provide context to the episode. After the weak trough passage on December 31, 1998 both primary and secondary pollutants accumulated once again leading to an exceedance of the 24-hour standard at Oildale-Manor, with a

PM 10 

### concentration of 156 μ g/m 3 

### on January 12, 1999 ( Figure 7 ). The next highest

PM 10 

### concentration measured was at Bakersfield-Golden with 109 μ g/m 3 

### . PM 10 

### concentrations at other central and southern Valley locations were below 90 μ g/m 3



### . During both periods, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore wind flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode. Chemical composition and meteorological data around December 31, 1998 and January 12, 1999, were evaluated and analyzed to identify the characteristics and uniqueness of the exceedances at Bakersfield-Golden, Visalia-Church, and Oildale-Manor.

The December 31, 1998 exceedances are not considered for compliance with the current Particulate Matter State Implementation Plan (SIP) because the exceedances fall outside of the three year required window. Although PM 10 

### sampling is not conducted daily, information from changes in the meteorological conditions suggest that the highest PM 10 

### concentration was not captured on the sampled day (December 31, 1998). Daily meteorological conditions suggested that the highest PM 10 

### concentrations may have occurred on December 29 th 

### , when stability was the strongest. With the lack of chemical data for Bakersfield-Golden, similarities in trends from other sites were analyzed in order to conclude which chemical components were responsible for the exceedance. The analysis shows that the exceedance was driven by high concentrations of ammonium nitrate and sulfate that comprised 74% of the PM 10 

### mass at nearby Bakersfield-California. At Visalia, the nitrate and sulfate chemical component
of the PM 10 

### sample was slightly higher compared to Bakersfield-California. These have accounted for the slight differences in the PM 10 

### mass between the two sites. The other major chemical components of the sample were 21% total carbon and 13% geological
of the PM 10 

### mass. The size fraction data across the Valley indicated that most of the

### 11 PM 10 

### was in the PM 2.5 

### fraction, with an average PM 2.5 

### /PM 10 

### mass ratio of greater than
0.8.

Figure 6: Bakersfield-Golden (Coarse, PM10, PM2.5) December 1998 & January 1999 Episode

0 20 40 60 80 100 120 140 160

1 2/20/1998 1 2/22/1998 1 2/24/1998 1 2/26/1998 1 2/28/1998 1 2/30/1998 1 /1/1999 1 /3/1999 1 /5/1999 1 /7/1999 1 /9/1999 1 /11/1999 1 /13/1999 1 /15/1999Particulate Matter (micrograms/cubic meter) BFL-Gold PM10

BFL-Gold Coarse

BFL-Gold PM2.5

Figure 7: Visalia and Oildale PM10 December 1998 & January 1999 Episode

0 20 40 60 80 100 120 140 160

1 2/ 2 0/

1 998 1 2/ 2 1/ 1 998 1 2/ 2 2/

1 998 1 2/ 2 3/

1 998 1 2/ 2 4/

1 998 1 2/ 2 5/

1 998 1 2/ 2 6/

1 998 1 2/ 2 7/

1 998 1 2/ 2 8/

1 998 1 2/ 2 9/

1 998 1 2/ 3 0/

1 998 1 2/ 3 1/ 1 998 1 /1 / 19

9 9 1 /2 / 19

9 9 1 /3 / 19

9 9 1 /4 / 19

9 9 1 /5 / 19

9 9 1 /6 / 19

9 9 1 /7 / 19

9 9 1 /8 / 19

9 9 1 /9 / 19

9 9 1 /1 0 /1 9 99 1 /1

1 /1 9 99 1 /1 2 /1 9 99 1 /1 3 /1 9 99 1 /1 4 /1 9 99 1 /1 5 /1 9 99 1 /1 6 /1 9 99Particulate Matter (micrograms/cubic meter) Vis PM10

Oildale PM10



### This was further supported by the high PM 2.5 

### concentrations that reached 122 μ g/m 3 

### at nearby Bakersfield-California accounting for 81 percent of the PM 10 

### mass and at Visalia
of 139 μ g/m 3 

### accounting for 83 percent of the PM 10 

### mass.

The concentration of coarse material may have been higher at the Bakersfield-Golden as is indicated by nearby Bakersfield-California and Visalia having the highest geological component of 13 μ g/m 3 

### compared to other Valley locations. Urban geological may have influenced the sample at Bakersfield-Golden and Visalia. Light afternoon mixing and wind flow may have allowed some transported contribution from agricultural burning in Merced, Stanislaus, and San Joaquin Counties on December
31 st 

### . However a no burn day across the rest of the Valley, indicates that stagnant

### 12 conditions favored a larger influence from local emissions. Burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Overnight minimum temperatures in the mid to upper 30’s suggest that residential wood burning may have been a significant source of PM 10 

### . The potential of increased residential wood burning on New Year’s Eve, may have led to increased concentrations of total carbon in the samples. Analysis of PM 10 

### and PM 2.5 

### concentrations showed that meteorological conditions led to the pollution buildup. Ammonium nitrate and sulfates, carbon, and geological material increased prior to the exceedances on December 31, 1998 and then later on January 12, 1999.

Meteorologically, dispersion worsened and particulate formation conditions strengthened from December 20 th 

### to the 29 th 

### . However, on December 31 st 

### , the exceedance day, dispersion conditions began to improve under decreasing stability. After the passage of a cold front on December 20 th 

### , which brought 0.10 inches of rainfall to Bakersfield, moisture was available for atmospheric chemistry reactions. Humidity measurements of 85 – 100 % in the morning across the Valley Floor showed a moist atmosphere with light fog and haze being reported. These cool damp mornings and strong stability favored the formation of nitrates and sulfates. Synoptically, the eastern Pacific high remained strong through December 29 th 

### and gradually weakened through
December 31 st 

### . The high rebuilt over the region on January 1 st 

### , keeping a lid over the San Joaquin Valley trapping pollutants within the Valley boundary layer through January 16, 1999.

With a strong lid in place and maximum high temperatures on December 31, 1998 in the mid to upper 50’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion for 14 hours on December 31, 1998 breaking out by 10:00 AM and reforming shortly after 7:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 4,500 feet), but the bulk of the day had limited to marginal mixing. Maximum temperatures for the December 1998 episode were slightly above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Satellite imagery depicted extensive moisture (high and mid-level cloudiness) across the region on the 31 st 

### , resulting in slightly lower levels of solar radiation intensity. Along with the lower solar radiation intensities due to the low sun angle and limited daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime.

Chemical composition and meteorological data showed with limited mixing depths and light and disorganized wind flow, these conditions resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions around Bakersfield-Golden and Visalia accumulated resulting in the exceedance of the
24-hour PM 10 

### standard on December 31, 1998.

Meteorological stability between December 31, 1998 and January 10, 1999 remained strong leading to moderate to elevated particulate conditions continuing across the San Joaquin Valley. Weak disturbances were moving through northern California prior to

### 13 the exceedance day, inhibiting widespread exceedance levels. The strong ridge that dominated the region’s weather finally began to breakdown on January 10, 1999, with decreasing stability. However, both primary and secondary pollutants from local emissions around Oildale-Manor accumulated resulting in an exceedance of the 24-
hour PM 10 

### standard on January 12, 1999 ( Figure 7 ); with nearby Bakersfield Golden recording a peak PM 10 

### concentration on the exceedance day of 109 μ g/m 3



### . Additionally, later on January 14, 1999 PM 2.5 

### monitoring at nearby Bakersfield California showed peak concentrations of 109 μ g/m 3 

### . Concentrations were dominated by the fine particulates (PM 2.5 

### ) of ammonia nitrate and sulfate and were most prevalent in the central and southern San Joaquin Valley. During the period, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore flow. Moisture from recent rainfall was available and strong morning stability contributed to the formation of nitrates and sulfates during the episode. These meteorological conditions led to elevated particulate concentrations. Chemical composition and meteorological data around January 12, 1999, was evaluated and analyzed to identify the characteristics and uniqueness of the exceedance at Oildale-Manor.

Although PM 10 

### sampling is not conducted daily, information from more frequent PM 2.5 

### sampling combined with an assessment of changes in the meteorological conditions suggest that the highest PM 10 

### concentration was not captured on the sampled day. Analysis of daily meteorological conditions suggested that the highest PM 10 

### concentrations may have occurred on January 10 th 

### , when stability was the strongest. Chemical data from Oildale-Manor showed that the exceedance was driven by high concentrations of ammonium nitrate and sulfate comprising about 57 % of the PM 10 

### mass. The size fraction data across the Valley indicated that most of the PM 10 

### was in
the PM 2.5 

### fraction, with an average PM 2.5 

### /PM 10 

### mass ratio of greater than 0.8. This was further supported by the high PM 2.5 

### concentrations that reached 84 μ g/m 3 

### at nearby Bakersfield-California.

The concentration of coarse material was minimal on the exceedance day, indicating that the majority of the sample was comprised of fine particulates. Agricultural burning may not have contributed as a potential source of PM on the exceedance day, because January 8 through January 12, 1999 were declared No Burn Day’s District-wide. However, burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Overnight minimum temperatures in the upper 20’s to low 30’s suggested that residential wood burning may have been a significant source of
PM 10 

### . Residential wood burning may have been a potential source of carbon. Concentrations of total carbon were measured at three sites in the Valley and ranged

from 12 μ g/m 3 

### at Modesto-14 th 

### Street to 27 μ g/m 3 

### at Fresno-1 st 

### . PM 10 

### and PM 2.5

### concentrations showed that meteorological conditions led to the exceedance at OildaleManor. Local sources of ammonia nitrate and sulfate coupled with moderately strong atmospheric stability resulted in the high PM 10 

### recorded at the exceedance site.

Meteorologically, dispersion conditions began to improve slightly a few days prior to the January 12, 1999 exceedance. After the passage of a weak cold front on December
20 th 

### , which brought 0.10 inches of rainfall to Bakersfield, some moisture was available

### 14 for atmospheric chemistry reactions. Humidity measurements of 85-95% in the morning across the Valley Floor showed a moist atmosphere, with light to dense fog and haze being reported. These cool damp mornings and strong stability favored the formation of nitrates and sulfates. Synoptically, the eastern Pacific high began to break down on the
10 th 

### , but stability remained strong across the region until the exceedance day. The high kept a strong lid in place over the Valley, trapping pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place and maximum high temperatures in the low to mid 50’s, the afternoon hours were marked by limited mixing, resulting in elevated particulate conditions. Mixing heights at Fresno remained below 500 feet for 21 hours on January

12 th 

### , breaking out by 3 P.M. and reforming shortly after 5:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 1,000 feet), but the bulk of the day had limited mixing. Light to dense fog was reported at the Valley surface during the morning hours of January 12 th 

### , resulting in lower solar radiation intensities. Along with lower solar radiation intensities due to the low sun angle and decreasing daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime.

Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. A major cause of the increase in PM10 at Oildale prior to January 12 appears to be from nitrates, which was more than double that concentration measured at Bakersfield California. This would suggest that something very localized or unique was occurring around Oildale that went beyond what was happening in other parts of the Valley. Both primary and secondary pollutants from local emissions around Oildale-Manor accumulated resulting in the exceedance of the 24-hour PM 10 

### standard on January 12,
1999.

### 15 

## 4.0 OCTOBER 21, 1999 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION

October 07-October 28, 1999

Throughout the San Joaquin Valley on October 21, 1999, several sites exceeded the
Federal 24-hour PM 10 

### Standard. These sites included: Fresno-Drummond Street at

162 μ g/m 3 

### , Corcoran-Patterson Avenue at 174 μ g/m 3 

### , and Turlock – S Minaret Street at

157 μ g/m 3 

### . In order to better understand the region wide occurrence of Particulate Material (PM) during this event, the synoptic meteorology, stability parameters, satellite imagery, atmospheric temperature profiles, and solar intensity measurements were investigated to determine the cause for the exceedances, which occurred on October 21, 1999.

Strong high pressure aloft and at the surface dominated the region’s weather throughout the month of October 1999. This month was characterized by above normal temperatures (+3.4 0 

### F) and below normal rainfall (-0.53 inches). The October 21, 1999 episode was preceded by deteriorating stability conditions after the passage of a weak trough into the Pacific Northwest on the 5 th



### . Figure 8 shows precipitation,
PM 2.5 

### , PM 10 

### , Model PM, and stability parameters for the October 1999 episode at the
Fresno-1 st 

### site.

Figure 8 also shows that the October 21 st 

### , 1999, episode was marked by a long period (21 days) of stable weather, with an average 500 MB height of 5,820 meters and 850 MB temperature of +16.4 0 

### C. According to Hackney et. al., both the 500 MB height and 850 MB temperature were highly suggestive of a PM 10 

### episode occurring. The San Joaquin Valley Air District uses regression equations to forecast PM 10 

### . As is evident in Figure 8 , Modeled PM 10 

### tracked closely with both the measured PM 10 

### and meteorological parameters. PM 10 

### /PM 2.5 

### ratios showed an increasing amount of fine particulates within the sample, representing a change from a more typical coarse dominate fall regime to an increasingly dominated fine particulate regime of late
November as is illustrated in Figure 8

.

### 16 Figure 8: Fresno- 1st PM10 and 2.5, Precipitation, T850 Stability, and Model PM10

October 1999

0 10 20 30 40 50 60 70 80 90 100 110 120 13010/1/199910/3/199910/5/199910/7/199910/9/199910/11/199910/13/199910/15/199910/17/199910/19/199910/21/199910/23/199910/25/199910/27/199910/29/199910/31/1999PM10 and PM2.5 (micrograms /meter^3) andPrecipitation /100

-10 -8 -6 -4 -2 0 2 4 6 8 10T850 Stability Parameter(C) PM10 Precipitation /100 (inches) T850 Stability
PM2.5
Model PM



### Next, winds speeds were analyzed during the exceedance date across the Valley. For example, at the Clovis monitoring site the 24 hour average wind speed was less than 2.2 knots (2.4 miles per hour). Since there was a strong high positioned across the region, the winds were calm in the morning becoming light thermally driven during the afternoon, resulting in minimal transport and dispersion. These weak winds are
indicative of historical PM 10 

### episodes.

These strong stable conditions continued through the 24 th 

### until the ridge began to
breakdown and move eastward on the 25 th 

### . A cool, dry trough moved into the Pacific
Northwest on the 28 th 

### , bringing good dispersion conditions, moderate to high boundary layer mixing heights and an end to the October 1999 episode.

The morning temperature profile from several sites were also investigated to determine the inversion strength and potential mixing depth. As is evident in figure 9 , the morning temperature profile measured at 4:00 a.m. from Fresno depicts a very strong inversion of 21 degrees Fahrenheit from the surface up to 1,500 feet, turning slightly isothermal (constant temperature) up to 3,000 feet. This type of strong trapping inversion was also evident in Sacramento (22 degrees Fahrenheit from the surface up to 1,500 feet) and Bakersfield (12 degrees Fahrenheit from the surface up to 2,000 feet). The strong morning inversions present across the region coupled with very light wind flow, trapped most pollutants near the surface in a very low mix layer throughout most of the day resulting in the elevated PM 10 

### measurements.

### 17 Figure 9: Atmospheric Temperature Profile at Fresno on October 21, 1999

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

50 55 60 65 70 75 80 85 90

Temperature (deg F)Feet (AGL)



### Another meteorological parameter investigated was solar intensity. Solar intensity for the month of October was also analyzed to determine if particulate material aloft or at the surface was lowering the solar radiation input, which drives both photochemical reactions and particulate matter formation. As is evident in figure 10 , three sites were analyzed; Madera, Parlier, and Arvin. It is evident especially with the solar intensity plot for Madera, that particulate matter was present over Madera, thus reducing the solar intensity measurement to below normal levels. This in effect, would change the atmospheric chemistry reactions from a more photochemistry-ozone forming regime to a more particulate regime that occurs during late November.

Figure 10: October 1999 Solar Intensity

0.00 0.20 0.40 0.60 0.80 1.00 1.20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

DateValue

Parlier 1200 Madera 1200 Arvin 1200 Madera Normal Poly. (Madera Normal)



### Satellite imagery analysis showed a weak low well off of Baja, drawing upper level moisture across the region. Varying amounts of high cloudiness were evident preceding the peak episode day and occurring through the 22 nd 

### . These clouds coupled with particulate aloft, drove the photochemistry reactions in the atmosphere into a fine particulate forming regime rather than an ozone forming regime.

Upon investigating the synoptic meteorology, stability parameters, atmospheric temperature profiles, and satellite imagery, these all are indicative of a widespread PM 10 

### event

, 

### occurring in the San Joaquin Valley on October 21, 1999.

### 18 

# 5.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND METEOROLOGY DURING THE OCTOBER 21, 1999 EPISODE

The October 21, 1999 particulate episode was characterized by a prolonged period (three weeks) of strong stability and light wind flow, which resulted in poor atmospheric dispersion conditions across the San Joaquin Valley. Coarse and fine particulates accumulated during the period, leading to an exceedance of the 24-hour PM 10 

### standard at three monitoring sites on October 21, 1999. Concentrations were dominated by geological particulates (PM 10 

### ), with significant contributions from fine particulates of ammonium nitrate and sulfate and total carbon and were most prevalent in the northern and central portions of the Valley and slightly lower in the southern portion (Kern County). The highest PM 10 

### concentration of 174 μ g/m 3 

### was measured at CorcoranPatterson (Figure 11) . The second and third highest PM 10 

### concentration of 162 and

157 μ g/m 3 

### were measured at Fresno-Drummond and Turlock, respectively (Figure 12)

. During the period, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore wind flow. Cool damp mornings and warm dry afternoons contributed to the geologic contribution, as well as nitrate and sulfate formation during the episode. A combination of these particulate species and poor dispersion conditions elevated particulate concentrations. Chemical composition and meteorological data around October 21, 1999, was evaluated and analyzed to identifythe characteristics and uniqueness of the exceedances at Corcoran-Patterson, FresnoDrummond, and Turlock- S Minaret.

Figure 11: Corcoran (Coarse, PM10 & PM2.5) and Fresno-1st (PM2.5) October 21, 1999 Episode

0 20 40 60 80 100 120 140 160 180

1 0 /7 /1 9 9 9 1 0 /8 /1 9 9 9 1 0 /9 /1 9 9 9 1 0 /1 0 /1 9 99 1 0 /1

1 /1 9 99 1 0 /1 2 /1 9 99 1 0 /1 3 /1 9 99 1 0 /1 4 /1 9 99 1 0 /1 5 /1 9 99 1 0 /1 6 /1 9 99 1 0 /1 7 /1 9 99 1 0 /1 8 /1 9 99 1 0 /1 9 /1 9 99 1 0 /2 0 /1 9 99 1 0 /2

1 /1 9 99 1 0 /2 2 /1 9 99 1 0 /2 3 /1 9 99 1 0 /2 4 /1 9 99 1 0 /2 5 /1 9 99 1 0 /2 6 /1 9 99 1 0 /2 7 /1 9 99 1 0 /2 8 /1 9 99Particulate Matter (micrograms/cubic meter) COR PM10

COR Coarse

COR PM2.5

FAT PM2.5



### Although PM 10 

### sampling is not conducted daily, information from more frequent PM 2.5 

### sampling combined with an assessment of changes in the meteorological conditions suggest that the highest PM 10 

### concentration was not captured on the sampled day. Daily PM 2.5 

### sampling and meteorological conditions suggested that the highest PM 10 

### concentrations may have occurred on October 20 th 

### , when Fresno 1 st 

### measured a peak

PM 2.5 

### concentration of 68 μ g/m 3



### . Chemical composition data indicated that geological material was the single largest component of the PM 10 

### during this episode.

### 19 Figure 12: Turlock-S Minaret and Fresno-Drummond (PM10) and Fresno-1st (PM2.5) October 21, 1999 Episode

0 20 40 60 80 100 120 140 160 180

1 0 /7 /1 9 9 9 1 0 /8 /1 9 9 9 1 0 /9 /1 9 9 9 1 0 /1 0 /1 9 99 1 0 /1

1 /1 9 99 1 0 /1 2 /1 9 99 1 0 /1 3 /1 9 99 1 0 /1 4 /1 9 99 1 0 /1 5 /1 9 99 1 0 /1 6 /1 9 99 1 0 /1 7 /1 9 99 1 0 /1 8 /1 9 99 1 0 /1 9 /1 9 99 1 0 /2 0 /1 9 99 1 0 /2

1 /1 9 99 1 0 /2 2 /1 9 99 1 0 /2 3 /1 9 99 1 0 /2 4 /1 9 99 1 0 /2 5 /1 9 99 1 0 /2 6 /1 9 99 1 0 /2 7 /1 9 99 1 0 /2 8 /1 9 99Particulate Matter (micrograms/cubic meter) FAT-Dru PM10

Turlock-Min PM10

FAT PM2.5



### While geological dominated the PM 10 

### mass, increases in other components (carbon, and ammonium nitrate and sulfate) were what drove the increase in concentration to
over the PM 10 

### Standard. It appears that the exceedance was driven by high concentrations of geologic comprising about 50 to 60 % of the PM 10 

### mass. The other components of the samples were composed of 15 to 25 % ammonium nitrate and
sulfate and 10 to 20 % total carbon of the PM 10 

### mass. The size fraction data across the Valley indicated that most of the PM 10 

### was in the PM 10 

### fraction, with an average
PM 2.5 

### /PM 10 

### mass ratio greater than 0.35. This was further supported by the high coarse

concentrations that reached 100 μ g/m 3 

### at Corcoran-Patterson, accounting for 57 percent of the PM10 mass (Figure 11).

The concentration of coarse material may have been elevated due to the lack of precipitation since June 2, 1999 contributing to the high geologic fraction. Dry conditions and low soil moisture content, resulted in higher dust emission activity from agricultural land preparing and harvesting and urban geological activities. Agricultural burning probably did not contribute to PM on the exceedance day, because October 17 through October 21, 1999 were declared No Burn Day’s District-wide. However, burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Overnight temperatures in the mid 50’s suggested that residential wood burning was not likely a potential source of PM 10 

### . PM 10 

### and PM 2.5 

### concentrations showed that meteorological conditions led to the pollution buildup.

Meteorologically, dispersion worsened and particulate formation conditions strengthened from October 7 th 

### to the 20 th 

### . However, on October 21 st 

### , the day of the exceedance, dispersion conditions began to slightly improve under weakening stability. The lack of precipitation since June 2 nd 

### , 1999 may have contributed to the geologic fraction. Dry conditions and low soil moisture content, resulted in higher dust emission activity. Humidity measurements of 60-80% in the morning across the Valley Floor

### 20 showed a dry to moist atmosphere, with no fog present. The cool damp mornings and strong stability favored some formation of nitrate and sulfate particulates. The eastern Pacific high built over the San Joaquin Valley on October 7 th 

### and dominated the region’s weather through the 20 th 

### . The high began to slowly break down on the 21 st 

### , but remained strong, trapping pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place aloft and maximum high temperatures in the mid-80’s, the afternoon hours were marked by limited mixing, resulting in elevated particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion
for 16 hours on the 21 st 

### , breaking out by 12:00 P.M. and reforming by 5:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth near 5,000 feet), but the bulk of the day had limited mixing. Maximum and minimum temperatures for the October 1999 were above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Partly cloudy skies and hazy conditions reported at the Valley surface on October 21 st 

### , resulted in lower levels of solar radiation intensities. Along with several wildfires to the north and along the California Coast and a major tire fire at Westley earlier in the month, particulate loading aloft may have further decreased solar radiation intensity measurements across the Valley Floor. The reduction of solar radiation intensity may have led to lower mixing depths and increased atmospheric chemistry reactions forming particulates. Ambient air samples around the Westley tire fire site on the 21 st 

### confirmed minimal hydrocarbon and carbon monoxide concentrations, showing little if any impact around the tire fire. However, visual observations of the tire fire plume behavior indicated transport and mixing well down-wind of the site, which may have fumigated and impacted other parts of the San Joaquin Valley.

With reduced solar radiation, the atmospheric chemistry reactions may have changed from the ozone-forming regime of mid-October to the secondary particulate regime that occurs during late November. The eight-hour average ozone measurements on
October 20 th 

### showed one exceedance of the Federal standard at Clovis of 87 ppb. The following day a significant change in the photochemical reactions occurred in the atmosphere, with the eight-hour average ozone measurements dropping to well below the standard at Clovis to 73 ppb. Atmospheric stability remained rather strong and persistent on the 21 st 

### , however, solar radiation measurements Valley-wide showed reduced intensities. The change in the ozone measurements across the San Joaquin Valley may be illustrative of the atmospheric chemistry reactions shifting from an ozone to a particulate-forming regime. The change in the atmospheric chemistry reactions may have led to an increase in nitrate and sulfate in the PM samples that were
measured on October 21 st 

### compared to the 15 th 

### . Increasing accumulations of carbon can be contributed to the deteriorating dispersion conditions experienced during the days preceding October 21 st 

### . It does not appear that any one source of carbon was a dominant contributor. Under the strong lid, wind flow was light and disorganized, leading to minimal transport and dispersion. As a result, local emissions may have contributed to the exceedances experienced on the 21 st



### .

### 21 Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants.
Solar radiation measurements showed lower levels of intensities on the 21 st 

### compared
to the 20 th 

### , resulting in an anomalous shift of the atmospheric chemistry reactions from an ozone to a particulate-forming regime. Both primary and secondary pollutants from local emissions around Corcoran-Patterson, Fresno-Drummond, and Turlock- S Minaret accumulated, resulting in the exceedance of the 24-hour PM 10 

### standard at three monitoring sites on October 21, 1999.

### 22 

## 6.0 NOVEMBER 14, 1999 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION

November 8 – November 17, 1999

After the trough passage on November 8 th 

### , which brought 0.31 inches of rainfall at Bakersfield, strong surface high pressure from the Intermountain Region and a 500 MB ridge from northwestern Mexico built into the region. These conditions lead to increasing stability and poor dispersion conditions through the exceedance date on
November 14 th



### , Figure 13.

Figure 13: T850 Stability and Precipitation vrs. PM10 and PM2.5

at Bakersfield Golden

Fall/Winter 1999

0 20 40 60 80 100 120 140 160 180 20010/1/199910/8/199910/15/199910/22/199910/29/199911/5/199911/12/199911/19/199911/26/199912/3/199912/10/199912/17/199912/24/199912/31/19991/7/20001/14/2000PM10 and PM2.5 (micrograms/meter^3) and Precipitation(inches)

-12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0T850 Stability Parameter (C) PM10 PPT PM2.5 Model PM T850 Stability



### At Bakersfield, Golden, a 24-hour PM 10 

### (Particulate Matter) concentration of 183 μ g/m 3



### was measured on the 14 th



### . Table 7 outlines federal reference method (FRM) Daily Average Particulate Matter Measurements for sites across the San Joaquin Valley (SJV). In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.

### 23 TABLE 7: Federal Reference Method (FRM) Daily Average Particulate Matter Measurements for sites across the SJV for November 14, 1999.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

10 2.5 10 2.5 10 2.5

Bakersfield-Gold 183 134 Modesto 67 70 Hanford 138

Bakersfield-CA 138 115 Merced-M St. 75 67 Stockton** 60 55

Visalia 137 121 Taft 70 Clovis 108 98

Fresno-1 st 

### 124 115 Fresno-Drum 130 Corcoran* 142 114

* -Patterson **- Hazleton

units in μ g/m 3



### The meteorological synoptic analysis showed after a period of moderately strong atmospheric stability from November 8 th 

### through the 17 th 

### , an upper level closed low from the eastern Pacific approached the region. Ahead of the closed low, strong stability occurred over the San Joaquin Valley trapping particulates within the Valley boundary layer. The morning surface charts on the 14 th 

### depicted a surface high pressure ridge draped across Central California from the Great Basin to San Francisco. The 12Zsurface pressure gradient was –3.6 millibars from San Francisco to Las Vegas (SFOLAS), with isobars (constant surface pressure) orientated northwest to southeast. With the alignment of the isobars and the –3.6 millibars pressure gradient, light offshore flow resulted in weak disorganized wind flow across the San Joaquin Valley. Visibilities throughout the day across the San Joaquin Valley were reporting haze.

The morning temperature aircraft sounding over Bakersfield showed a strong inversion (stable layer) of 17 degrees Fahrenheit from the surface up to 2,000 feet as is evident in Figure 14. At Fresno the temperature sounding showed a similar strong inversion of 24 degrees Fahrenheit from the surface up to 2,000 feet. The temperature soundings on
the 14 th 

### are conducive of elevated PM levels due to low mixing depths, which keep pollutants trapped near the surface. At surface observations across the San Joaquin Valley, minimum temperature at Fresno was 48 degrees Fahrenheit and Bakersfield was 49 degrees Fahrenheit.

### 24 Figure 14: Atmospheric Temperature Profile at Bakersfield on November 14, 1999

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

50 55 60 65 70 75 80

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a strong high over the Four Corners Region, with a ridge extending westward across California. At 850 MB a temperature ridge built northwestward across the San Joaquin Valley from southern California. A closed low was positioned 600 NM west of Santa Barbara. The pressure gradient across the San Joaquin Valley remained weak during the day leading to light and disorganized wind flow across the region. Table 8 shows the 24 hour daily average wind speeds at SJVAPCD air monitoring, ASOS, and CIMIS sites for November 14, 1999. The 24 hour daily average wind speeds across the Valley floor were conducive to elevated PM readings over the central and southern parts of the San Joaquin Valley.

### 25 Table 8 shows the 24 hour daily average wind speeds at SJVAPCD monitoring, ASOS, and CIMIS sites for November 14, 1999.

SJVAPCD Monitoring Sites ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 3.9 Fresno 4.1 Shafter/USDA 3.5 Famoso 3.1

Fresno SSP 2.0 Bakersfield 6.1 Firebaugh/Telles 3.5 Westlands 3.9

Corcoran 3.0 Hanford 2.9 Stratford 3.0 Panoche 4.5

Edison 2.3 Kettleman 4.1 Arvin-Edison 3.2

Parlier 3.6 Visalia/Americas 2.4 Lindcove 1.9

Arvin 2.1 Parlier 3.0 Kesterson 3.2

Visalia 1.4 Blackwells Corner 5.4 Fresno State 3.4

Los Banos 4.2 Modesto 3.1

Manteca 2.9



### Due to the strong stability lasting for over 9 days, PM 10 

### steadily increased region-wide
until November 14 th



### , 1999. Light disorganized wind flow, a strong morning inversion, limited mixing depths, and strong stability aloft; lead to limited dispersion conditions on
the 14 th 

### causing local PM emissions in Bakersfield Golden to increase past the Federal

24-hour PM 10 

### standard to 183 μ g/m 3 

### . Since the other FRM Monitoring sites did not register above the Federal 24-hour PM 10 

### standard on the 14 th 

### , the Bakersfield Golden
PM 10 

### measurement may signify impacts from local emission sources.

Other FRM Monitoring sites across the central and southern San Joaquin Valley (Visalia, Fresno, Hanford, Clovis, and Corcoran) measured 24-hour PM 10 

### above 100

μ g/m 3 

### , but did not exceed the Federal 24-hour PM 10 

### standard. A weak upper level disturbance moved through the region late on the 14 th 

### and 15 th 

### , bringing better dispersion conditions and lowering Bakersfield’s PM measurements to less the National Ambient Air Quality Standard.

### 26 

# 7.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND
METEOROLOGY DURING THE NOVEMBER 1999 EPISODE

The November 14, 1999 particulate episode was characterized by a short period (9 days) of strong stability and light wind flow, which resulted in poor atmospheric dispersion conditions across the San Joaquin Valley. Coarse and fine particulates accumulated during the period, leading to an exceedance of the 24 - hour standard at one monitoring site on November 14, 1999. Concentrations were dominated by the fine particulates (PM 2.5 

### ) of ammonia nitrate and sulfate and were most prevalent in the central and southern San Joaquin Valley. The highest PM 10 

### measured was 183 μ g/m 3 

### ( Figure 15 ) at Bakersfield-Golden; whereas, PM 10 

### concentrations at other central and southern Valley locations were much lower between 130 to 140 μ g/m 3 

### ( Figure 16 )

. During the period, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore wind flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode. These meteorological conditions led to elevated particulate concentrations. Chemical composition and meteorological data around November 14, 1999, was evaluated and analyzed to identify the characteristics and uniqueness of the exceedance at
Bakersfield-Golden.

Figure 15: Bakersfield Golden (PM2.5 & Coarse) and Fresno 1st (PM2.5) November 14, 1999 Episode

0 20 40 60 80 100 120 140 160 180 200

1 1 /6 /1 9 9 9 1 1 /7 /1 9 9 9 1 1 /8 /1 9 9 9 1 1 /9 /1 9 9 9 1 1 /1 0 /1 9 99 1 1 /1

1 /1 9 99 1 1 /1 2 /1 9 99 1 1 /1 3 /1 9 99 1 1 /1 4 /1 9 99 1 1 /1 5 /1 9 99 1 1 /1 6 /1 9 99 1 1 /1 7 /1 9 99Particulate Matter (micrograms / cubic meter) BAK-GOLD Coarse

BAK-GOLD PM2.5

FAT-1st PM2.5



### Although PM 10 

### sampling is not conducted daily, information from more frequent PM 2.5 

### sampling combined with an assessment of changes in the meteorological conditions suggest that the highest PM 10 

### concentration was captured on the sampled day. With no chemical composition data available at the exceedance site, similarities in trends from other sites were analyzed in order to conclude which chemical components were responsible for the exceedance. It appears that the exceedance was driven by high concentrations of ammonium nitrate and sulfate comprising about 50 to 60 % of the
PM 10 

### mass. The other chemical components of the samples were composed of 10 to 15 % total carbon and 10 to 15% geological of the PM 10 

### mass. The size fraction data across the Valley indicated that most of the PM 10 

### was in the PM 2.5 

### fraction, with an

### 27 Figure 16: Bakersfield California (PM2.5, PM10, & Coarse) and Fresno 1st (PM2.5)
November 14, 1999 Episode

0 20 40 60 80 100 120 140 160

11/6/1 999 11/7/1 999 11/8/1 999 11/9/1 999 11/10 /1999 11/11 /1999 11/12 /1999 11/13 /1999 11/14 /1999 11/15 /1999 11/16 /1999 11/17 /1999Particulate Matter (micrograms/cubic meter) BAK-CA PM10

BAK-CA Coarse

BAK-CA PM2.5

FAT-1st PM2.5



### average PM 2.5 

### /PM 10 

### mass ratio of greater than 0.8. This was further supported by the high PM 2.5 

### concentrations that reached 134 μ g/m 3 

### at the exceedance site, accounting for 73 percent of the PM 10 

### mass, ( Figure 15 ). All monitoring sites exceeded the federal
PM 2.5 

### standard on the exceedance day.

The concentration of coarse material may have been higher at the exceedance site relative to other sites in the Valley, as indicated by the higher coarse fraction at Bakersfield Golden as compared to other sites in the Valley. The coarse mass at Bakersfield-Golden, at 49 μ g/m 3 

### , was 26 μ g/m 3 

### higher compared to nearby BakersfieldCalifornia, indicating that a larger concentration of urban geological material at Bakersfield-Golden may be responsible for the large disparity in the PM 10 

### concentrations. Agriculture burning probably did not contribute to PM on the exceedance day, because November 13 and 14, 1999 were declared No Burn Day’s District-wide. However, burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Although minimum temperatures were mild compared to later in the middle of winter, overnight temperatures in the mid to upper 40’s suggest that residential wood burning may have been a potential source of
PM 10 

### . PM 10 

### and PM 2.5 

### concentrations showed that meteorological conditions led to the short pollution buildup. During the buildup time leading to the exceedance on November 14, 1999, carbon concentrations decreased or remained stable, whereas concentrations of geologic, ammonia nitrate, and sulfate increased.

Meteorologically, dispersion worsened and particulate formation conditions strengthened from November 8 th 

### to the 14 th 

### . After the passage of a cold front on
November 8 th 

### , which brought 0.31 inches of rainfall to Bakersfield, moisture was available for atmospheric chemistry reactions. Humidity measurements of 85-100% in the morning across the Valley Floor showed a very moist atmosphere, with light to dense fog and haze being reported. The cool damp mornings and strong stability favored the formation of nitrates and sulfates. The eastern Pacific high built over the San Joaquin Valley on November 8 th 

### and dominated the region’s weather through the

### 28 14 th 

### . The high strengthened and intensified a few days prior to the 14 th 

### , further tightening the lid and trapping pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place and maximum high temperatures in the mid to upper 70’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion for 16 hours on November 14, 1999 breaking out by 11:00 AM and reforming shortly after 5:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing. Maximum and minimum temperatures for the November 1999 episode were above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Satellite imagery depicted scattered upper level moisture (high cloudiness) over the region and light fog being reported at the Valley surface on the November 14, resulting in slightly lower levels of solar radiation intensity. Along with lower solar radiation intensities due to the low sun angle and decreasing daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime.

Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions around Bakersfield-Golden accumulated, resulting in the exceedance of the 24-hour PM 10 

### standard on November 14, 1999.

### 29 

## 8.0 DECEMBER 17 AND 23, 1999 EPISODE SYNOPTIC
METEOROLOGICAL DISCUSSION

December 10 – December 31, 1999

The period from December 10, 1999 through December 31 st 

### , 1999 was marked by 21 days of strong stability and poor atmospheric dispersion conditions. Strong high pressure over the Intermountain Region dominated the period, leading to light and disorganized wind flow and limited dispersion. The period began with the passage of a weak cold front and trough on the 9 th 

### . Between the 10 th 

### and the 17 th 

### , increasing stability and poor dispersion conditions resulted in a PM 10 

### exceedance at Corcoran on the 17 th



### , Figure 17.

Figure 17: T850 Stability and Precipitation at Hanford vrs. PM10 and PM2.5

at Corcoran

December 1999

39 81

58 59
49 174

115 135 145 139

0 20 40 60 80 100 120 140 160 180 20012/1/199912/2/199912/3/199912/4/199912/5/199912/6/199912/7/199912/8/199912/9/199912/10/199912/11/199912/12/199912/13/199912/14/199912/15/199912/16/199912/17/199912/18/199912/19/199912/20/199912/21/199912/22/199912/23/199912/24/199912/25/199912/26/199912/27/199912/28/199912/29/199912/30/199912/31/1999PM10 and PM2.5 (micrograms/meter^3) andPrecipitation (inches)/100

-12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0T850 Stability Parameter (C) PPT PM10 Model PM PM2.5 T850 Stability



### At Corcoran, a 24-hour PM 10 

### (Particulate Matter) concentration of 174 μ g/m 3 

### was measured. Table 9 outlines federal reference method (FRM) Daily Average Particulate Matter measurements for sites across the San Joaquin Valley (SJV). In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.

### 30 TABLE 9: Federal Reference Method (FRM) Daily Average Particulate Matter measurements for sites across the SJV for December 17, 1999.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

10 2.5 10 2.5 10 2.5

Bakersfield-Gold 92 Modesto 99 93 Corcoran* 174

Bakersfield-CA 111 90 Merced-M St. 75 Stockton** 78

Visalia 114 Clovis 18 Fresno-1 st 

### 107

* -Patterson **- Hazleton

units in μ g/m 3



### The meteorological synoptic analysis showed a period of moderately strong atmospheric stability from December 10 th 

### through the 17 th 

### . Ahead of a developing trough over the eastern Pacific, a strong mid and upper level ridge developed over the region on the 17 th 

### . This ridge strengthened the inversion over the San Joaquin Valley trapping particulates within the Valley boundary layer. The morning surface charts of
the 17 th 

### depicted a strong surface high over the Great Basin and Intermountain Region. The 12Z (4 a.m.) surface pressure gradient was +1.8 millibars from San Francisco (SFO) to Las Vegas (LAS), with isobars (constant surface pressure) orientated west to east. The alignment of the isobars and the +1.8 millibars pressure gradient, represents light and disorganized wind flow across the San Joaquin Valley. Visibilities throughout the day across the San Joaquin Valley were reporting haze.

The morning temperature aircraft sounding over Fresno on the 17 th 

### showed multiple inversions, with a strong inversion (stable layer) of 13 degrees Fahrenheit from the surface up to 1,000 feet, with a secondary strong inversion of 11 degrees Fahrenheit from 2,500 to 5,000 feet as is evident in Figure 18. The morning temperature sounding over Bakersfield also showed multiple inversions, with a strong inversion of 15 degrees Fahrenheit from the surface up to 3,000 feet, with a secondary strong inversion of 11 degrees Fahrenheit from 4,500 feet to 5,000 feet. The temperature sounding on the

17 th 

### , is conducive of elevated PM levels due to low mixing depths and multiple inversions, which keep pollutants trapped near the surface. During the early morning surface observations across the San Joaquin Valley were cold. The minimum temperatures recorded at Fresno and Bakersfield were 33 degrees Fahrenheit. The maximum high temperatures recorded at Fresno and Bakersfield were 59 degrees Fahrenheit. Fresno hourly temperature data shows very limited mixing conditions below 500 feet for over 18 hours of the day, increasing with minor afternoon heating to a

### 31 maximum mixing depth of 2,000 feet on the 17 th



### .

Figure 18: Atmospheric Temperature Profile at Fresno on December 17, 1999

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

35 40 45 50 55 60 65

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a strong high just west of Santa Barbara, with a ridge building northeastward into the Great Basin. A weak trough over the extreme Pacific Northwest extended southward to near Eureka. Weak pressure gradients across the San Joaquin Valley remained rather flat through the day, leading to light and disorganized wind flow across the San Joaquin Valley.

Table 10 shows the 24 hour daily average wind speeds at SJVAPCD monitoring, ASOS, and CIMIS sites for December 17, 1999.

SJVAPCD Monitoring Sites ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 2.2 Fresno 1.7 Shafter/USDA 2.1 Famoso 2.4

Fresno SSP 1.4 Bakersfield 3.4 Firebaugh/Telles 2.2 Westlands 2.6

Corcoran 2.8 Hanford 1.0 Stratford 2.4 Panoche 2.6

Edison 3.3 Kettleman 2.6 Arvin-Edison 2.3

Parlier 3.2 Visalia/Americas 2.1 Lindcove 1.8

Arvin 2.2 Parlier 2.2 Kesterson 2.4

Visalia 1.6 Blackwells Corner 2.0 Lodi West 1.8

Los Banos 2.8 Modesto 2.9

Manteca 2.4 Fresno State 2.2



### Due to the strong stability lasting for over 7 days, PM 10 

### steadily increase region-wide until the sampling day on December 17 th 

### . With the mid and upper level stability aloft, surface based inversion, and light and disorganized wind flow, this weather pattern was conducive of an elevated region-wide PM 10 

### measurements. At Visalia and Fresno 1 st



### , fine particulates were above 100 μ g/m 3 

### , further suggesting a widespread PM event across the San Joaquin Valley.

### 32 After a weak upper level trough passage on the 18 th 

### , strong high pressure rebuilt into the region from the eastern Pacific, with increasing stability and poor dispersion conditions through the next exceedance date on December 23 rd 

### at Fresno-Drummond Street and Hanford-Irwin Street. At Fresno-Drummond, a 24-hour PM 10 

### concentration
of 168 μ g/m 3 

### and at Hanford a 24-hour PM 10 

### concentration of 156 μ g/m 3 

### was measured.

Table 11 Federal Reference Method (FRM) Daily Average Particulate Matter and Table
12 California Regional Particulate Air Quality Study (CRPAQS) Measurements shows for sites across the San Joaquin Valley (SJV) for December 23. In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.
TABLE 11: Federal Reference Method (FRM) Daily Average Particulate Matter Measurements for sites across the SJV for December 23, 1999.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

10 2.5 10 2.5 10 2.5

Bakersfield-Gold 74 Modesto 119 95 Corcoran* 135 91

Bakersfield-CA 109 72 Merced-M St. 83 Stockton** 79

Visalia 85 Clovis 22 Fresno-1st 119

* -Patterson #-Wagner, **- Hazleton

TABLE 12: California Regional Particulate Air Quality Study (CRPAQS) Daily Average
Particulate Matter Measurements for Fresno-Drummond and Hanford-Irwin for December 23, 1999. CRPAQS Site Name 24-Avg.

10

Fresno-Drummond 168

Hanford-Irwin 156

units in μ g/m 3 

### for Table 11 and 12

The meteorological synoptic analysis showed after a period of strong atmospheric stability from December 18 th 

### through the 23 rd 

### , increasing stability and poor dispersionconditions lead to two exceedances measured using CRPAQS monitors at FresnoDrummond and Hanford, Figure 19 . The morning surface charts on the 23 rd 

### depicted a surface ridge extending southwestward across the central San Joaquin Valley from strong highs anchored over the Intermountain Region. The morning surface pressure gradient was –1.6 millibars from San Francisco to Las Vegas (SFO-LAS), with isobars (constant surface pressure) orientated southeast to northwest. With the alignment of the isobars and –1.6 millibars pressure gradient, this represents light southeasterly wind

### 33 flow across the San Joaquin Valley. Visibilities across the San Joaquin Valley throughout the day reported hazy conditions.

Figure 19: T850 Stability and Precipitation vrs. PM10 and PM2.5

at Hanford

December 1999

0 20 40 60 80 100 120 140 160 18012/1/199912/2/199912/3/199912/4/199912/5/199912/6/199912/7/199912/8/199912/9/199912/10/199912/11/199912/12/199912/13/199912/14/199912/15/199912/16/199912/17/199912/18/199912/19/199912/20/199912/21/199912/22/199912/23/199912/24/199912/25/199912/26/199912/27/199912/28/199912/29/199912/30/199912/31/1999PM10 and PM2.5 (micrograms/meter^3) and Precipitation(inches)/100

-12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0T850 Stability Parameter(C) PPT FRM PM10 CRPAQS PM10 Model PM T850 Stability



### The morning temperature aircraft sounding over Fresno depicted a strong inversion (stable layer) of 19 degrees Fahrenheit from the surface up to 1,000 feet as is evident in Figure 20. Bakersfield showed a strong inversion of 12 degrees Fahrenheit from the surface up to 1,000 feet turning isothermal up to 3,000 feet. The temperature soundings on the 23 rd 

### are indicative of elevated PM levels due to low mixing depths and strong inversions, which trap pollutants near the surface. During the early morning surface observations across the San Joaquin Valley were cold. The minimum temperatures recorded at Fresno and Bakersfield were 34 and 36 degrees respectively. The maximum high temperatures recorded at Fresno and Bakersfield were 62 and 64 degrees Fahrenheit respectively. Fresno hourly temperature data shows very limited mixing conditions below 500 feet for over 16 hours of the day, increasing with minor afternoon heating to a maximum mixing depth of 2,000 feet on the 23 rd

### 34 Figure 20: Atmospheric Temperature Profile at Fresno on December 23, 1999

0 1000 2000 3000 4000 5000

35 40 45 50 55 60

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a strong high 600 NM west of Santa Barbara, with a ridge building northward along the West Coast into the eastern Gulf of Alaska. Pressure gradients remained weak throughout the day leading to poor dispersion conditions across the San Joaquin Valley.

Table 13 shows the 24 hour daily average wind speeds at SJVAPCD monitoring, ASOS, and CIMIS sites for December 23, 1999.

SJVAPCD Monitoring Site ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 2.5 Fresno 1.5 Shafter/USDA 2.5 Famoso 2.5

Fresno SSP 2.1 Bakersfield 3.1 Firebaugh/Telles 2.5 Westlands 3.0

Corcoran 3.3 Hanford 1.6 Stratford 3.3 Panoche 2.7

Edison 3.7 Kettleman 3.3 Arvin-Edison 2.6

Parlier 3.9 Visalia/Americas 2.5 Lindcove 1.8

Arvin 2.4 Parlier 2.7 Kesterson 2.1

Visalia 1.7 Blackwells Corner 2.1 Lodi West 1.7

Los Banos 2.8 Modesto 2.4

Manteca 2.4 Fresno State 2.3



### The period of December 10, 1999 through December 31 st 

### , 1999, marked one of the longest periods of strong stability in recent history. This pattern was similar to the one experienced during the California Regional Particulate Air Quality Study. The main difference between the two episodes was the CRPAQS event began a week later and continued into the early part of January. During the exceedances of 1999, they were preceded by an exceptionally dry fall. After a weak frontal passage on the 10 th 

### , which brought a cold air mass to the Valley, this air remained trapped within the Valley boundary layer resulting in strong surface based inversions. Coupled with the synoptic and surface pattern, which was indicative of light and disorganized wind flow, PM became a region-wide problem until a weak trough scoured out the area on New Year’s Eve. As is evident in the PM data, local emissions contributed to the exceedance of the National Ambient Air Quality Standards at Corcoran on the 17 th 

### and Fresno-Drummond,
and Hanford on the 23 rd 

### . If monitoring were done on a daily basis, more exceedances would have been recorded during this time frame at other San Joaquin Valley locations.

### 35 

## 9.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND
METEOROLOGY DURING THE DECEMBER 1999 EPISODE

The December 1999 particulate episode was characterized by a prolonged period (three weeks) of strong stability and light wind flow, which resulted in poor atmospheric dispersion conditions across the San Joaquin Valley. Coarse and fine particulates accumulated during the period, leading to two separate exceedance days on December 17 and 23, 1999. Concentrations were dominated by fine particulates (PM 2.5 

### ) of ammonia nitrate and sulfate and were most prevalent in the central and southern San Joaquin Valley. The highest PM 10 

### measured on December 17, 1999 was 174 μ g/m 3 

### ( Figure 21 ) at Corcoran, a federal reference monitoring (FRM) site. PM 10 

### at other central and southern Valley locations were elevated but not over the standard. For example, Fresno-Drummond recorded 153 μ g/m 3 

### on December 17, 1999 ( Figure 22 ). Stagnation conditions continued through December 23, 1999, when two MiniVol Samplers, which were part of the California Regional Particulate Air Quality Study(CRPAQS) registered the second and third highest concentrations at FresnoDrummond at 168 μ g/m 3 

### and Hanford-South Irwin, at 156 μ g/m 3 

### . The CRPAQS exceedances are not considered for compliance with the standards, but are used in the discussion to provide context to the episode. During the period, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore wind flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode. Chemical composition and meteorological data around December 17 and 23, 1999 were evaluated and analyzed to identify the characteristicsand uniqueness of the exceedances at Corcoran, Fresno-Drummond, and HanfordSouth Irwin.

Figure 21: Corcoran (PM2.5, PM10 & Coarse) and Fresno 1st (PM2.5)
December 17, 1999 Episode

0 20 40 60 80 100 120 140 160 180

1 2 / 11/1

9 9 9 1 2 / 12/1

9 9 9 1 2 / 13/1

9 9 9 1 2 / 14/1

9 9 9 1 2 / 15/1

9 9 9 1 2 / 16/1

9 9 9 1 2 / 17/1

9 9 9 1 2 / 18/1

9 9 9 1 2 / 19/1

9 9 9 1 2 / 20/1

9 9 9 1 2 / 21/1

9 9 9 1 2 / 22/1

9 9 9 1 2 / 23/1

9 9 9 1 2 / 24/1

9 9 9 1 2 / 25/1

9 9 9 1 2 / 26/1

9 9 9 1 2 / 27/1

9 9 9 1 2 / 28/1

9 9 9 1 2 / 29/1

9 9 9 1 2 / 30/1

9 9 9 1 2 / 31/1

9 9 9 1 /1/2

0 0 0Particulate Matter (micrograms / cubic meter) Corcoran PM10

Corcoran Coarse

Corcoran PM2.5

FAT-1st PM2.5

### 36 Figure 22: Fresno Drummond (PM10) and Fresno 1st (PM2.5) December 17, 1999 Episode

0 20 40 60 80 100 120 140 160 180

1 2/

1 1/ 1 999 1 2/

1 2/

1 999 1 2/

1 3/

1 999 1 2/

1 4/

1 999 1 2/

1 5/

1 999 1 2/

1 6/

1 999 1 2/

1 7/

1 999 1 2/

1 8/

1 999 1 2/

1 9/

1 999 1 2/ 2 0/

1 999 1 2/ 2 1/ 1 999 1 2/ 2 2/

1 999 1 2/ 2 3/

1 999 1 2/ 2 4/

1 999 1 2/ 2 5/

1 999 1 2/ 2 6/

1 999 1 2/ 2 7/

1 999 1 2/ 2 8/

1 999 1 2/ 2 9/

1 999 1 2/ 3 0/

1 999 1 2/ 3 1/ 1 999 1 /1 / 20

0 0Particulate Matter (micrograms/cubic meter) FAT-DRU PM10

FAT-1st PM2.5



### Although PM 10 

### sampling is not conducted daily, information from more frequent PM 2.5 

### sampling combined with an assessment of changes in the meteorological conditions suggest that the highest PM 10 

### concentration was not captured on the sample day. Daily
PM 2.5 

### sampling and meteorological conditions suggested that the highest PM 10 

### concentrations may have occurred on December 18 th 

### , when Fresno 1 st 

### measured a peak PM 2.5 

### concentration of 119 μ g/m 3 

### . With the lack of chemical composition data for the exceedance site, similarities in trends from other sites such as Fresno-Drummond were drawn in order to determine the chemical components responsible for the
December 17 th 

### exceedance. The analysis shows that the exceedance was driven by high concentrations of ammonium nitrate and sulfate that comprised of 55 to 75 % of
the PM 10 

### mass. The other major chemical components of the samples were 25 to 30 % total carbon and 20 to 25 % geological of the PM 10 

### mass. The size fraction data across the Valley indicated that most of the PM 10 

### was in the PM 2.5 

### fraction, with an average
PM 2.5 

### /PM 10 

### mass ratio greater than 0.8. This was further supported by the high PM 2.5 

### concentrations that reached 107 μ g/m 3 

### at nearby Fresno-First, ( Figure 22 )

.

The concentration of total carbon (27% of PM 10 

### mass) and coarse material (20% of
PM 10 

### mass) at Fresno Drummond show the main constituents of the particulate samples on December 17, 1999 may have come from local sources (residential wood burning and urban/agricultural geologic). Light afternoon mixing and wind flow may have allowed some transported contribution from agricultural burning in Merced, Stanislaus, and San Joaquin Counties on December 17 th 

### . However a no burn day across the rest of the Valley, indicates that stagnant conditions favored a larger influence from local emissions. Burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Overnight minimum temperatures in the low 30’s suggest that residential wood burning may have been a significant source of PM 10



### . Analysis of PM 10 

### and PM 2.5 

### concentrations showed that meteorological conditions led to the pollution buildup. Ammonium nitrate and sulfates, carbon, and geological material increased prior to the exceedance on December 17, 1999 and then later accumulated further leading to two other monitoring sites exceedances on December 23.

### 37 Meteorologically, dispersion worsened and particulate formation conditions strengthened from December 10 th 

### to the 17 th 

### . After the passage of a weak cold front on
December 9 th 

### , which brought trace amounts of precipitation to the region, moisture was available for atmospheric chemistry reactions. Humidity measurements of 85 – 100 % in the morning across the Valley Floor showed a moist atmosphere, with light to dense fog and haze being reported. These cool damp mornings and strong stability favored the formation of nitrates and sulfates. Synoptically, the eastern Pacific high built over the San Joaquin Valley on December 10 th 

### and dominated the region’s weather through
the 31 st 

### . The high strengthened and intensified a few days prior to the 17 th 

### , further tightening the lid and trapping pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place aloft and maximum high temperatures in the upper 50’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion
for 18 hours on December 17 th 

### , breaking out after 12:00 P.M and reforming shortly before 5:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing. Maximum and minimum temperatures for this episode were slightly above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog was reported at the Valley surface during the early morning
hours of December 17 th 

### , resulting in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the early morning fog, lowering sun angle, and decreasing daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime.

Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions around Corcoran accumulated resulting in the exceedance of the 24- hour PM 10 

### standard on December 17, 1999.

Between December 17 th 

### through the 23 rd 

### , meteorological conditions remained stable leading to elevated particulate conditions continuing across the San Joaquin Valley. Without a significant weather disturbance moving through the area to scour out the particulates, PM 10 

### concentrations became a region-wide problem and came very close to the standard at three monitoring sties (Fresno-1 st 

### at 154 μ g/m 3 

### , Visalia at 152 μ g/m 3



### , and Clovis at 151 μ g/m 3 

### ) on December 20, 1999. PM 10 

### concentrations from FresnoDrummond and Hanford climbed between December 17 th 

### through the 23 rd 

### , while PM 10 

### concentrations at Corcoran lowered during this time frame. Due to the light winds and limited mixing, local emission activity around Corcoran may have lowered leading to decreasing PM 10 

### levels. Analysis of total carbon and ammonium nitrates and sulfates indicates that Fresno-Drummond and Hanford registered higher levels compared to Corcoran, indicating potentially that local emissions sources may have impacted these
sites. A few days later, two MiniVol Samplers, which were collected as part of the California Regional Particulate Air Quality Study (CRPAQS), measured the second and

### 38 third highest concentrations at Fresno-Drummond at 168 μ g/m 3 

### (Figure 22) and Hanford-South Irwin, at 156 μ g/m 3 

### (Figure 23). The CRPAQS exceedances are not considered for compliance with the standards, but are used in the discussion to provide context to the episode.

Figure 23: Hanford (PM10) and Fresno 1st (PM2.5) December 23, 1999 Episode

0 20 40 60 80 100 120 140 160 180

1 2/ 11

/1 99

9 1 2/ 12

/1 99

9 1 2/ 13

/1 99

9 1 2/ 14

/1 99

9 1 2/ 15

/1 99

9 1 2/ 16

/1 99

9 1 2/ 17

/1 99

9 1 2/ 18

/1 99

9 1 2/ 19

/1 99

9 1 2/ 20

/1 99

9 1 2/ 21

/1 99

9 1 2/ 22

/1 99

9 1 2/ 23

/1 99

9 1 2/ 24

/1 99

9 1 2/ 25

/1 99

9 1 2/ 26

/1 99

9 1 2/ 27

/1 99

9 1 2/ 28

/1 99

9 1 2/ 29

/1 99

9 1 2/ 30

/1 99

9 1 2/ 31

/1 99

9 1 /1 / 200

0Particulate Matter (micrograms/cubic meter) HNF PM10

FAT-1st PM2.5



### Although PM 10 

### sampling is not conducted daily, information from more frequent PM 2.5 

### sampling combined with an assessment of changes in the meteorological conditions suggest that the highest PM 10 

### concentration was not captured on the sampled day. Daily PM 2.5 

### sampling and meteorological conditions suggested that the highest PM 10 

### concentrations may have occurred on December 24 th 

### and 25 th



### , when Fresno 1 st


### measured peak PM 2.5 

### concentrations of 134 and 131 μ g/m 3 

### , respectively. The exceedances at Fresno-Drummond and Hanford-Irwin were driven by high concentrations of ammonia nitrate and sulfate and/or total carbon, which accumulated
between December 17 th 

### and the 23 rd 

### . The size fraction data across the Valley
indicated that most of the PM 10 

### was in the PM 2.5 

### fraction, with an average PM 2.5 

### /PM 10 

### mass ratio greater than 0.7. This was further supported by the high PM 2.5 

### concentrations that reached 119 μ g/m 3 

### at nearby Fresno-First, ( Figure 22 & 23).

The concentration at Fresno-Drummond of ammonium nitrate and sulfate (74 μ g/m 3 

### ), total carbon (44 μ g/m 3 

### ), and geological (44 μ g/m 3 

### ), had the highest PM 10 

### mass in the Valley. The concentration at Hanford of ammonium nitrate and sulfate (80 μ g/m 3 

### ), total carbon (35 μ g/m 3 

### ), and geological (44 μ g/m 3 

### ), had the second highest PM 10 

### mass in the Valley. The main constituents of the particulate samples on December 23, 1999 may have come from local sources (residential wood burning and urban/agricultural geologic). Agricultural burning may not have contributed as a potential source of PM on the exceedance day, because since December 18, 1999 were declared a No Burn Day’s District-wide. However, burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Overnight minimum temperatures in the low to mid 30’s suggest that residential wood burning was likely to be a significant

### 39 source of PM 10 

### . It appears that potentially residential burning may have been a source
of carbon. PM 10 

### and PM 2.5 

### concentrations showed that meteorological conditions led to the pollution buildup. During the buildup time leading to the two separate exceedances on December 23, 1999, where ammonium nitrate and sulfates, carbon, and geological
material increased.

Meteorologically, dispersion conditions began to slightly improve a few days prior to the
December 23 rd 

### exceedances. The lack of precipitation since December 9 th 

### may have contributed to the increasing geological component. Humidity measurements of 85 – 100 % in the morning across the Valley Floor showed a moist atmosphere, with light to dense fog and haze being reported. The cool damp mornings and strong stability favored the formation of nitrates and sulfates. The eastern Pacific high remained strong through the 20 th 

### and gradually weakened through the 31 st 

### , keeping a tight lid over the San Joaquin Valley trapping the pollutants within the Valley boundary layer.

With a strong lid in place aloft and maximum high temperatures in the low 60’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion
for 16 hours on the December 23 rd 

### , breaking out shortly after 12:00 P.M and reforming before 5:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing. Maximum temperatures for this episode were above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog reported at the Valley surface during the early morning hours, resulted in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the low sun angle and decreasing daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime.

In summary, chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions around Fresno-Drummond and Hanford-Irwin accumulated resulting in the exceedance of the
24-hour PM 10 

### standard on December 23, 1999.

### 40 

## 10.0 DECEMBER 1999 AND JANUARY 2000 PM 2.5 

## & PM 10 

## METEOROLOGICAL DISCUSSION

During December 1999 and January 2000 episode, strong high pressure at the surface and aloft resulted in limited morning and afternoon mixing and light offshore flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode. The December 1999 and January 2000 episode can be divided
into three distinct events (Figure 24). These events, characterized by limited atmospheric dispersion, were separated by trough passages.

Each event was marked by limited mixing heights with strong inversions of approximately 500 feet for 18 or more hours of the day. Maximum mixing depths on the highest PM 2.5 

### concentration days ranged between 1,000 to 2,500 feet. Moisture availability from recent rainfall and minimal solar insulation, led to prime nitrate and sulfate forming conditions. Typically, light fog, with humidity measurements between 85 – 100% were needed in order to maximize particulate forming potential. The higher the humidity, the heavier and wetter the fog, results in the removal of particulates by wet deposition.

Within these three distinct measurement periods, a violation of the Federal 24 hour
PM 2.5 

### National Ambient Air Quality Standard (NAAQS) of 65 micrograms / meter 3 

### were recorded during the 1 st 

### and 3 rd 

### events at some locations across the San Joaquin Valley (Figure 25). The following analysis will investigate the meteorological and dispersion conditions surrounding each event.

Figure 24: T850 Stability vrs. PM 10 and PM 2.5 at Corcoran for December 1999 and January 2000

39 81

58 59

49 174

115 135 145 139

113 128

0 20 40 60 80 100 120 140 160 180 20012/1/199912/2/199912/3/199912/4/199912/5/199912/6/199912/7/199912/8/199912/9/199912/10/199912/11/199912/12/199912/13/199912/14/199912/15/199912/16/199912/17/199912/18/199912/19/199912/20/199912/21/199912/22/199912/23/199912/24/199912/25/199912/26/199912/27/199912/28/199912/29/199912/30/199912/31/19991/1/20001/2/20001/3/20001/4/20001/5/20001/6/20001/7/20001/8/20001/9/20001/10/20001/11/20001/12/2000PM10and PM2.5(micrograms/meter3)

-12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0T850 Stability Parameter(Celsius) FRM PM10

T850 Hanford Stability

FRM 2.5

Event #1 Event #2 Event #3



### *No precipitation occurred in Hanford from December 1, 1999 through January 12, 2000.

### 41 Event #1: December 1 through December 8, 1999

Atmospheric dispersion worsened and particulate formation conditions became more
favorable from December 1 st 

### to December 6 th 

### in the San Joaquin Valley. As is evident
in Figure 25, event #1 lasted about 9 days and was marked by one main PM 2.5 

### peak, which exceeded the NAAQS. After the passage of a cold front on December 1, 1999, which brought trace amounts of precipitation across the San Joaquin Valley, moisture became available for atmospheric chemistry reactions. Humidity measurements of 85 – 100 % in the morning across the Valley Floor showed a moist air mass, with light fog and haze being reported on the 6 th 

### . These cool damp mornings and strong stability favored the formation of nitrates and sulfates. Since concentrations rose through the episode, it does not appear that the water content of the atmosphere was high enough to create deposition of particles that exceeded formation.

Synoptically, during the first part of event #1, the eastern Pacific ridge built over
northern California on December 5 th 

### then expanded southward on the 6 th 

### , bringing increasing stability and poor dispersion conditions through the 7 th 

### . With a strong lid in place aloft and maximum high temperatures in the upper 50’s on the 6 th 

### , the afternoon hours were marked by limited mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion during a majority of the day (20 or more hours) on the 6 th 

### . During the afternoon hours, there were moderate mixing depths of 1,500 feet but the bulk of the day had limited mixing. Maximum and minimum temperatures were near to slightly below normal, indicating a potential for increasing residential wood burning emission activity, and nitrate forming
reactions.

Meteorological data during event #1 showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions across the San Joaquin Valley accumulated resulting in the exceedance of the 24 hour PM 2.5 

### NAAQS at Fresno-1 st 

### on December 6 th 

### . No other sites registered an exceedance on or around December 6 th



### , thus indicating that local emissions drove the measurement above the NAAQS.

A cold front moved into northern California on the 7 th 

### and 8 th 

### , bringing an end to event
#1 that lasted from December 1 st 

### through the 8 th 

### . The disturbance brought moderate dispersal conditions across the Valley, allowing pollutants to lower into the 20 to 30 micrograms per cubic meter range, but was not significant enough to drop PM 2.5 

### levels to background.

Event #2: December 9 through December 31, 1999

The period from December 9, 1999 through December 31 st 

### , 1999 was marked by 22 days of strong stability and poor atmospheric dispersion conditions. Strong high pressure over the Intermountain Region dominated the period, leading to light and disorganized wind flow and limited dispersion. The period began with the passage of a

### 42 weak cold front and trough on the 9 th 

### . Between the 10 th 

### and the 17 th 

### , increasing stability and poor dispersion conditions resulted in a PM 10 

### exceedance at Corcoran on the 17 th



### .

Figure 25: PM 2.5 at Fresno 1 st and Bakersfield California
for December 1999 and January 2000

0 20 40 60 80 100 120 14012/1/199912/3/199912/5/199912/7/199912/9/199912/11/199912/13/199912/15/199912/17/199912/19/199912/21/199912/23/199912/25/199912/27/199912/29/199912/31/19991/2/20001/4/20001/6/20001/8/20001/10/20001/12/2000PM2.5(micrograms / meter3) Fresno-1st Street

Bakersfield-5558 California Avenue

Event #1 Event #2 Event #3



### At Corcoran, a 24-hour PM 10 

### (Particulate Matter) concentration of 174 μ g/m 3 

### was measured. Table 14 outlines federal reference method (FRM) Daily Average Particulate Matter measurements for sites across the San Joaquin Valley (SJV). In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.

TABLE 14: Federal Reference Method (FRM) Daily Average Particulate Matter measurements for sites across the SJV for December 17, 1999.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

10 2.5 10 2.5 10 2.5

Bakersfield-Gold 92 Modesto 99 93 Corcoran* 174

Bakersfield-CA 111 90 Merced-M St. 75 Stockton** 78

Visalia 114 Clovis 18 Fresno-1 st 

### 107

* -Patterson **- Hazleton

units in μ g/m 3



### The meteorological synoptic analysis showed a period of moderately strong atmospheric stability from December 10 th 

### through the 17 th 

### . Ahead of a developing trough over the eastern Pacific, a strong mid and upper level ridge developed over the region on the 17 th 

### . This ridge strengthened the inversion over the San Joaquin Valley

### 43 trapping particulates within the Valley boundary layer. The morning surface charts of
the 17 th 

### depicted a strong surface high over the Great Basin and Intermountain Region. The 12Z (4 a.m.) surface pressure gradient was –3.9 millibars from San Francisco (SFO) to Reno (RNO) (SFO-RNO), with isobars (constant surface pressure) orientated west to east. The alignment of the isobars and the –3.9 millibars pressure gradient, represented offshore wind flow across the San Joaquin Valley. Many sites across the San Joaquin Valley were reporting haze.

The morning temperature aircraft sounding over Fresno on the 17 th 

### showed multiple inversions, with a strong inversion (stable layer) of 13 degrees Fahrenheit from the surface up to 1,000 feet, with a secondary strong inversion of 11 degrees Fahrenheit from 2,500 to 5,000 feet as is evident in Figure 26. The morning temperature sounding over Bakersfield also showed multiple inversions, with a strong inversion of 15 degrees Fahrenheit from the surface up to 3,000 feet, with a secondary strong inversion of 11 degrees Fahrenheit from 4,500 feet to 5,000 feet. The temperature sounding on the

17 th 

### , is conducive of elevated PM levels due to low mixing depths and multiple inversions, which keep pollutants trapped near the surface. During the early morning surface observations across the San Joaquin Valley were cold. The minimum temperatures recorded at Fresno and Bakersfield were 33 and 43 degrees Fahrenheit respectively. The maximum high temperatures recorded at Fresno and Bakersfield were 59 and 57 degrees Fahrenheit respectively. Fresno hourly temperature data shows very limited mixing conditions below 500 feet for over 18 hours of the day, increasing with minor afternoon heating to a maximum mixing depth of 2,000 feet on the

17 th



### .

Figure 26: Atmospheric Temperature Profile at Fresno on December 17, 1999

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

35 40 45 50 55 60 65

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a strong high just west of Santa Barbara, with a ridge building northeastward into the Great Basin. A weak trough over the extreme Pacific Northwest extended southward to near Eureka. Weak pressure gradients across the San Joaquin Valley remained rather flat through the day, leading to light and disorganized wind flow across the San Joaquin Valley.

### 44 Table 15 shows the 24 hour daily average wind speeds at SJVAPCD monitoring, ASOS, and CIMIS sites for December 17, 1999.

SJVAPCD Monitoring Sites ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 2.2 Fresno 1.7 Shafter/USDA 2.1 Famoso 2.4

Fresno SSP 1.4 Bakersfield 3.4 Firebaugh/Telles 2.2 Westlands 2.6

Corcoran 2.8 Hanford 1.0 Stratford 2.4 Panoche 2.6

Edison 3.3 Kettleman 2.6 Arvin-Edison 2.3

Parlier 3.2 Visalia/Americas 2.1 Lindcove 1.8

Arvin 2.2 Parlier 2.2 Kesterson 2.4

Visalia 1.6 Blackwells Corner 2.0 Lodi West 1.8

Los Banos 2.8 Modesto 2.9

Manteca 2.4 Fresno State 2.2



### Due to the strong stability lasting for over 7 days, PM 10 

### steadily increase region-wide until the sampling day on December 17 th 

### . With the mid and upper level stability aloft, surface based inversion, and light and disorganized wind flow, this weather pattern was conducive of an elevated region-wide PM 10 

### measurements. Light south – southeast to west – northwest transport wind flow of 4 to 6 miles per hour occurred during a few

hours on the 17 th 

### . At Visalia and Fresno 1 st 

### , fine particulates were above 100 μ g/m 3



### , further suggesting a widespread PM event across the San Joaquin Valley.

After a weak upper level trough passage on the 18 th 

### , strong high pressure rebuilt into the region from the eastern Pacific, with increasing stability and poor dispersion conditions through the next exceedance date on December 23 rd 

### at Fresno-Drummond Street and Hanford-Irwin Street. At Fresno-Drummond, a 24-hour PM 10 

### concentration
of 168 μ g/m 3 

### and at Hanford a 24-hour PM 10 

### concentration of 156 μ g/m 3 

### was measured.

Table 16 Federal Reference Method (FRM) Daily Average Particulate Matter and Table
17 California Regional Particulate Air Quality Study (CRPAQS) Measurements shows for sites across the San Joaquin Valley (SJV) for December 23. In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode was
done.

### 45 TABLE 16: Federal Reference Method (FRM) Daily Average Particulate Matter Measurements for sites across the SJV for December 23, 1999.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

10 2.5 10 2.5 10 2.5

Bakersfield-Gold 74 Modesto 119 95 Corcoran* 135 91

Bakersfield-CA 109 72 Merced-M St. 83 Stockton** 79

Visalia 85 Clovis 22 Fresno-1 st 

### 119
* -Patterson #-Wagner, **- Hazleton

TABLE 17: California Regional Particulate Air Quality Study (CRPAQS) Daily Average
Particulate Matter Measurements for Fresno-Drummond and Hanford-Irwin for December 23, 1999. CRPAQS Site Name 24-Avg.

10

Fresno-Drummond 168

Hanford-Irwin 156

units in μ g/m 3 

### for Table 16 and 17



### The meteorological synoptic analysis showed after a period of strong atmospheric stability from December 18 th 

### through the 23 rd 

### , increasing stability and poor dispersion
conditions lead to two exceedances of the PM 10 

### NAAQS measured using CRPAQS monitors at Fresno-Drummond and Hanford, Figure 27 . The morning surface charts on
the 23 rd 

### depicted a surface ridge extending southwestward across the central San Joaquin Valley from strong highs anchored over the Intermountain Region. The morning surface pressure gradient was –7.6 millibars from San Francisco to Reno (SFO-RNO), with isobars (constant surface pressure) orientated southeast to northwest. With the alignment of the isobars and –7.6 millibars pressure gradient, this represented light to moderate offshore wind flow across the San Joaquin Valley. Light southeasterly transport wind flow of 5 to 8 miles per hour occurred for a few hours of the day. .

Visibility reports across the San Joaquin Valley indicated hazy conditions throughout the day.

### 46 Figure 27: T850 Stability and Precipitation vrs. PM10

at Hanford

December 1999

0 20 40 60 80 100 120 140 160 18012/1/199912/2/199912/3/199912/4/199912/5/199912/6/199912/7/199912/8/199912/9/199912/10/199912/11/199912/12/199912/13/199912/14/199912/15/199912/16/199912/17/199912/18/199912/19/199912/20/199912/21/199912/22/199912/23/199912/24/199912/25/199912/26/199912/27/199912/28/199912/29/199912/30/199912/31/1999PM10 (micrograms/meter^3)

-12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0T850 Stability Parameter(C) FRM PM10

CRPAQS PM10

Model PM10 T850 Stability



### *No precipitation occurred in Hanford from December 1, 1999 through December 31, 1999.



### The morning temperature aircraft sounding over Fresno depicted a strong inversion (stable layer) of 19 degrees Fahrenheit from the surface up to 1,000 feet as is evident in Figure 28. Bakersfield showed a strong inversion of 12 degrees Fahrenheit from the surface up to 1,000 feet turning isothermal up to 3,000 feet. The temperature soundings on the 23 rd 

### are indicative of elevated PM levels due to low mixing depths and strong inversions, which trap pollutants near the surface. During the early morning surface observations across the San Joaquin Valley were cold. The minimum temperatures recorded at Fresno and Bakersfield were 34 and 36 degrees respectively. The maximum high temperatures recorded at Fresno and Bakersfield were 62 and 64 degrees Fahrenheit respectively. Fresno hourly temperature data shows very limited mixing conditions below 500 feet for over 16 hours of the day, increasing with minor afternoon heating to a maximum mixing depth of 2,000 feet on the 23 rd

Figure 28: Atmospheric Temperature Profile at Fresno on December 23, 1999

0 1000 2000 3000 4000 5000

35 40 45 50 55 60

Temperature (deg F)Feet (AGL)

### 47 Upper level charts indicated a strong high 600 NM west of Santa Barbara, with a ridge building northward along the West Coast into the eastern Gulf of Alaska. Pressure gradients remained weak throughout the day leading to poor dispersion conditions across the San Joaquin Valley.

Table 18 shows the 24 hour daily average wind speeds at SJVAPCD monitoring, ASOS, and CIMIS sites for December 23, 1999.

SJVAPCD Monitoring Site ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 2.5 Fresno 1.5 Shafter/USDA 2.5 Famoso 2.5

Fresno SSP 2.1 Bakersfield 3.1 Firebaugh/Telles 2.5 Westlands 3.0

Corcoran 3.3 Hanford 1.6 Stratford 3.3 Panoche 2.7

Edison 3.7 Kettleman 3.3 Arvin-Edison 2.6

Parlier 3.9 Visalia/Americas 2.5 Lindcove 1.8

Arvin 2.4 Parlier 2.7 Kesterson 2.1

Visalia 1.7 Blackwells Corner 2.1 Lodi West 1.7

Los Banos 2.8 Modesto 2.4

Manteca 2.4 Fresno State 2.3



### The period of December 9, 1999 through December 31 st 

### , 1999, marked one of the longest periods of strong stability in recent history. This pattern was similar to the one experienced during the California Regional Particulate Air Quality Study. The main difference between the two episodes was the CRPAQS event began a week later and continued into the early part of January. During the exceedances of 1999, they were preceded by an exceptionally dry fall. After a weak frontal passage on the 10 th 

### , which brought a cold air mass to the Valley, this air remained trapped within the Valley boundary layer resulting in strong surface based inversions. Coupled with the synoptic and surface pattern, which was indicative of light and disorganized wind flow, PM became a region-wide problem until a weak trough scoured out the area on New Year’s Eve. As is evident in the PM data, local and regional emissions contributed to the exceedance of the NAAQS at Corcoran on the 17 th 

### and Fresno-Drummond, and
Hanford on the 23 rd 

### . If monitoring were done on a daily basis, more exceedances would have been recorded during this time frame at other San Joaquin Valley locations. Event #2 ended when a cold front from the Gulf of Alaska moved through the region bringing enhanced dispersion across the San Joaquin Valley, lowering pollutant levels
to below the PM 2.5 

### NAAQS.

Event #3 January 1 through January 12, 2000:

Meteorologically, dispersion once again worsened and particulate conditions became more favorable from January 1 st 

### to January 10 th 

### . As is evident in Figure #2, event #3 lasted about 12 days and was marked by multiple violations of the PM 2.5 

### NAAQS. After the passage of a weak cold front on January 1, 2000, which brought trace amounts of precipitation to the San Joaquin Valley, moisture became available for atmospheric

### 48 chemistry reactions. Humidity measurements of 85 – 100 % in the morning across the Valley Floor showed a moist air mass, with light fog and haze being reported.

Synoptically, during event #3 a weak ridge dominated along the California Coastline directing upper level disturbances into the Pacific Northwest. The ridge was strong enough to gradually, through a period of a few days, cause a localized PM 2.5 

### problem centered at the urban areas, which spread outward toward the rural areas and become a regional problem, especially across the central and southern parts of the San Joaquin Valley. The fast upper level flow pattern was positioned over the Pacific Northwest through event #3, with multiple embedded disturbances within this flow. California remained on the southern periphery (stable side) of this flow pattern. With a moderate lid in place aloft and maximum temperatures in the mid to upper 50’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a moderate inversion during most of the day (16 hours or more). During the afternoon hours there were moderate mixing depths of 1,500 to 2,000 feet but the bulk of the day had limited mixing. Maximum and minimum temperatures were near or slightly below normal, indicating a potential for higher residential wood burning emission activity and nitrate forming
reactions.

Meteorological data during event #3 showed limited mixing depths and light north to northwesterly wind flow resulted in minimal dispersion of pollutants. Both primary and secondary pollutants from local emissions across the metropolitan areas of the San Joaquin Valley accumulated resulting in an exceedance of the 24 hour PM 2.5 

### NAAQS atseveral sites on January 7, 2000. These sites included: Merced, Chowchilla, Fresno1 st 

### , Clovis-Villa, Selma, Visalia-Church, Corcoran-Patterson, Kettleman, Pixley Wildlife Refuge, Oildale, and Bakersfield Golden and California. Since both rural and urban areas registered PM 2.5 

### levels above the NAAQS, these violations continued through the
10 th 

### of January at most locations. A dry cold front moved through the region on January 12, 2000, providing adequate northwesterly flow, resulting in PM 2.5 

### levels lowering below the NAAQS.

### 49 Figure 29: Wind Rose at Clovis Air Monitoring Site for 12/17 and 12/23/1999, and
01/07/2000

### 50

### 51 

## 11.0 DECEMBER 2000 AND JANUARY 2001 EPISODE SYNOPTIC
METEOROLOGICAL DISCUSSION

The CRPAQS fall and winter measurement periods can be divided into seven distinct episodes. These episodes, characterized by limited atmospheric dispersion, were separated by vigorous trough passages. Analysis of synoptic events shows that once a particulate episode begins, a deep trough must traverse the region at both the upper levels of the atmosphere and at the surface as a cold frontal boundary in order to significantly decrease Particulate Matter (PM) concentrations. These types of troughs are normally associated with strong vertical mixing, moderate to high boundary layer mixing heights, precipitation, and wind speed and directional sheer within the boundary layer.

The meteorological analysis for CRPAQS utilized synoptic analyses, precipitation patterns, and atmospheric stability parameters to determine episode strength and periodicity. Analysis of PM 2.5 

### /PM 10 

### ratios and nitrate levels reveal that when the overnight minimum temperature decreased to below 40 degrees Fahrenheit, coupled with significant warming aloft, fine particulate levels climbed. When prolonged periods of these conditions occurred, PM 2.5 

### levels climbed above the NAAQS. In even stronger more persistent stability regimes, PM 10 

### exceeded the NAAQS. Figure 30 shows precipitation, PM 2.5 

### , PM 10 

### , and stability parameters for the CRPAQS period at the
Fresno-1 st 

### site. General patterns in these parameters where also evident at other sites. Precipitation events also influenced PM concentrations during CRPAQS. For the CRPAQS period, when a frontal system was strong enough to produce precipitation of 0.10 inch or more of liquid water, 24 hour averaged PM 2.5 

### concentrations dropped to

below 15 μ g/m 3



### .

### 52 Figure 30: Fresno-1 st 

### Stability and Pollutant Trends for
Fall 2000 & Winter 2001

0 20 40 60 80 100 120 140 160 180 200

10 / 1 / 2000 10

/ 4 / 2000 10

/ 7 / 2000 10

/ 1 0 /2000 10

/ 1 3 /2000 10

/ 1 6 /2000 10

/ 1 9 /2000 10

/ 2 2 /2000 10

/ 2 5 /2000 10

/ 2 8 /2000 10

/ 3 1 /2000 11

/ 3 / 2000 11

/ 6 / 2000 11

/ 9 / 2000 11

/ 1 2 /2000 11

/ 1 5 /2000 11

/ 1 8 /2000 11

/ 2 1 /2000 11

/ 2 4 /2000 11

/ 2 7 /2000 11

/ 3 0 /2000 12

/ 3 / 2000 12

/ 6 / 2000 12

/ 9 / 2000 12

/ 1 2 /2000 12

/ 1 5 /2000 12

/ 1 8 /2000 12

/ 2 1 /2000 12

/ 2 4 /2000 12

/ 2 7 /2000 12

/ 3 0 /2000 1/2/2001 1/5/2001 1/8/2001 1/11

/ 2001 1/14

/ 2001 1/17

/ 2001 1/20

/ 2001 1/23

/ 2001 1/26

/ 2001 1/29

/ 2001 2/1/2001 -10 -5 0 5 10 15 20 PM10 (micrograms per cubic meter) Precipitation*100 (inches) PM 2.5 (micrograms/cubic meter) T850-T(FAT MIN) (Celsius)



## 12 3 7 5 4 6 Start of Episode



### The synoptic meteorological parameters analyzed to determine the behavior of particulate matter were 850 MB temperature stability (T850 Stability 0 

### C), 500 MB height (decameters), and precipitation (inches). The 850 MB temperature stability parameter was utilize because 850 MB temperature (approximately 5,000 feet) minus the minimum surface temperature is a good indicator of the inversion strength, the mixing layer depth, and whether air is being warmed from a synoptic subsidence inversion aloft. This inversion is commonplace when a ridge builds along the West Coast of California, providing general adiabatic warming of subsiding air over the region. In Hackney, et al, an analysis was conducted on the relationship of historical 850 MB temperatures and PM measurements. Hackney, et al, determined that in the San Joaquin Valley, when 850 MB temperatures in the fall were above +15 0 

### C and +10 0 

### C during the winter (late November or December to February) an episode was possible. A stronger indication for a PM episode to occur is when 850 MB temperatures were above +18 0 

### C in the fall
and above +14 0 

### C in the winter.

500 MB height is also important in that it is directly correlated to the temperature of the entire column of air. During periods of high pressure aloft, flows at the surface are usually light and accompanied by low mixing depths. The 500 MB height and placement of the mean ridge and trough patterns reflect PM amounts and trends. In Hackney, et al, it was determined that a height of 5,760 meters in the San Joaquin Valley is sufficient to suspect an episode, and that a height of 5,820 meters or more in the Valley made an episode occurrence a likelihood.

### 53 Precipitation measurements were also analyzed as an indicator of the vigorous trough passages, which provided enough vertical mixing to produce rainfall. As mentioned before, the strength of the frontal system and trough, was a good indicator of how much PM dispersion occurred.

Table 19 shows for each peak day within the seven episodes, the PM values, meteorological parameters, and episode duration. The major episode of CRPAQS, when PM10 exceeded the NAAQS, was manifested by cool overnight lows near 32 degrees Fahrenheit and warm air aloft for an extended period of time. These conditions persisted from December 17 th 

### through January 7 th 

### . During this time, PM steadily increased to a peak value at Fresno (PM 2.5 

### = 148 μ g/m 3 

### and PM 10 

### = 193 μ g/m 3 

### ) and Bakersfield-Residential (PM 2.5 

### =133 μ g/m 3 

### ) on the 1 st 

### of January. During this period in urban areas, initial analysis of speciation data show high carbon and ammonium nitrate levels. The combination of an 850 MB temperature ridge aloft along with low minimum temperatures resulted in strong inversions trapping pollutants in a shallow mix layer. The high carbon levels could have been due to holiday residential wood combustion. In addition, under these cold and poor dispersion conditions, nitrate levels measured on the real-time instruments were the highest of the study.

TABLE 19: CRPAQS EPISODE EVENT SUMMARY TABLE AT FRESNO

One basis for understanding the behavior of particulate matter evolution is to analyze the synoptic situation that is driving the local effects of dispersion and transport. These synoptic descriptions follow. Episode
Number 

### Date Peak
PM 10 

### ( μ g / m 3 

### ) Peak
PM 2.5 

### ( μ g / m 3 

### ) T850 Stability ( 0 

### C) Minimum ( 0 

### F) 500 MB Height (dm) Episode
Duration (days)

1 10/1-
10/12/00 42(6 th 

### ) 24 (5 th 

### &
6 th 

### ) 2.4 63 578 12

2 10/13-
10/30/00 67(18 th 

### ) 47 (18 th 

### ) 6.8 54 578 18

3 10/31-
11/15/00 57 (2 nd 

### ) 61 (4 th 

### ) 2.3 47 575 17

4 11/16-
12/15/00 114 (20 th 

### ) 90 (20 th 

### ) 89 (28 th 

### ) 9.3
6.2 35
46 576
572 28

5 12/16/00-
01/12/01 193 (1 st 

### ) 148 (1 st 

### ) 12.6 32 574 26

6 01/13-
01/27/01 104 (19 th 

### ) 103(21 st 

### ) 3.9(19 th 

### ) 6.8(21 st 

### ) 38 (19 th 

### ) 33 (21 st 

### ) 571(19 th 

### ) 569(21 st 

### ) 15

7 01/28-
02/03/01 47 (31 st 

### ) 73 (3 rd 

### ) 3.9(31 st 

### ) 6.1(3 rd 

### ) 34 (31 st 

### ) 39 (3 rd 

### ) 568(31 st 

### ) 580(3 rd 

### ) 7

### 54 Episode 1: Sunday, October 1 -Thursday, October 12

From the 1 st 

### to the 8 th 

### , episode #1 was marked by a mean, broad ridge anchored across the eastern Pacific and California, which brought moderate stability and low to moderate mixing heights. This ridge was low in amplitude, resulting in moderate subsidence. An inverted thermal surface trough developed from Bakersfield curving northwestward to Redding. This pressure pattern was representative of calm overnight winds, and thermally driven light afternoon northwesterly flow. During this initial episode, PM 2.5 

### values average near 20 μ g/m 3 

### and measured PM 10 

### concentration at Fresno was 42

μ g/m 3 

### on the 6 th 

### . The 500 MB height of 578 dm on the 6 th 

### was conducive of a high PM event, whereas, the 850 MB stability parameter of +2.4 Celsius (T850 MB = +20 0 

### C) was indicative of the likelihood of an event. As is evident in the low T850 MB stability parameter, the inversion and resulting stability was not strong enough to trap and elevate PM readings, thus resulting in PM levels remaining well below the standard.

A significant early season trough moved into the region on the 9 th 

### , bringing increasing instability and boundary layer flow. Within the next couple of days, the 9 th 

### to the 12 th 

### , a series of disturbances embedded within the mean trough traversed central California bringing increased wind flow, higher boundary layer mixing heights, and precipitation. The most noteworthy precipitation during this period occurred on the 11 th 

### , when a second short wave embedded within the mean trough across California crossed the Valley and produced 0.76 inches of precipitation.

Episode 2: Friday, October 13 –Monday, October 30

Episode #2 was marked by high pressure rapidly building into the region on the 13 th 

### and persisting through the 20 th. 

### This episode was unique in that the central California was under the influence of both the eastern Pacific and Four Corners ridge during the peak episode day. This pattern resulted in weak thermally driven flow at the surface and general synoptic subsidence aloft. As a result, under light to moderate stability, T850 stability parameter of +2.8 0 

### C (T850 MB = 15 0 

### C), moderately high 500 MB heights (578 MB) and low mixing depths, PM climbed and reached a maximum concentration in

Fresno at PM 10 

### – 67 μ g/m 3 

### and PM 2.5 

### – 47 μ g/m 3 

### and Bakersfield at PM 2.5 

### – 30 μ g/m 3 

### on the 18 th 

### . According to Hackney, et, al, the 850 MB temperature and 500 MB heights reached the criteria to suspect an episode. As is evident in the PM measurements the
state standard was exceeded in Fresno on the 18 th



### .

The ridge began to breakdown on the 20 th 

### as weak disturbances traversed the ridge
and formed a closed low over the Great Basin on the 24 th 

### . Another stronger trough moved into the region on the 25 th 

### bringing moderate boundary layer flow, vigorous vertical mixing, and periods of precipitation through the 30 th 

### . With the trough passage
on the 29 th 

### , Fresno recorded the maximum amount of precipitation during the episode of
0.55 inches.

Episode 3: Tuesday, October 31 –Wednesday, November 15

### 55 Episode #3 began on the 31 st 

### as a strong ridge developed along the West Coast. The ridge axis remained offshore during this episode leading to downstream subsidence and increasing stability. During the peak PM event of episode #3, Bakersfield’s PM values were lower than Fresno due to a closed low circulation over northern Baja, creating some upper level mixing and neutral to light instability over southern California. As a result, the peak PM 2.5 

### levels at Bakersfield Residential were 45 μ g/m 3 

### , with a T850 MB stability parameter of +1.4 0 

### C (T850 MB = +9.2 0 

### C) and 500 MB height of 575 dm on the

3 rd 

### and at Fresno First PM 10 

### measurement of 57 μ g/m 3 

### on the 2 nd 

### and PM 2.5 

### measurement 61 μ g/m 3 

### , with a 850 MB stability parameter of +2.3 0 

### C (T850 MB = +10.6

0 

### C) and 500 MB height of 575 dm on the 4 th



### .

In both Fresno and Bakersfield, according to Hackney et, al, the T850 MB and 500 MB heights do not suggest an episode under a fall regime; however, the PM10
measurement in Fresno exceeded the standard on the 2 nd 

### . Whereas, comparing Hackney et, al, results under a winter regime to the observed T850 MB, their conclusion supported a minor PM episode. Due to early season rainfall and a general cooling of the lower levels of the atmosphere, the transition from the fall to the winter regime took place during this time.

PM levels steadily lowered as the upper level ridge and surface high pressure gradually weakened and moved eastward. An unseasonably cold trough (540 dm at OAK) and a vigorous, dry cold front from the Gulf of Alaska moved into the region on the 9 th



### , bringing increased boundary layer flow and deep mixing. This system was moisture starved and resulted in trace amounts of precipitation across the region. The frontal system and accompanying trough were strong enough to bring an end to the 3 rd 

### episode as deep mixing scoured the area. Multiple embedded disturbances within this trough traversed the region bringing unstable conditions, good dispersive conditions, and moderate boundary layer flow and mixing heights into the 15 th



### .

Episode 4: Thursday, November 16 –Friday, December 15

Episode #4 began on the 16 th 

### and was marked by a moderate ridge building along the West Coast bringing increasing stability and offshore flow. During CRPAQS the 4 th 

### episode was the longest period at 28 days.

Stability and PM values steadily increased to the highest measured values of the episode on the 20 th 

### and 21 st 

### of November, with a secondary peak occurring on the 28 th



### . This episode was separated into two peaks due to a trough developing over the Great
Basin on the 22 nd 

### dispersing some of the PM which had built up over the region. Fresno and Bakersfield peak PM 2.5 

### measurements were observed on the 20 th 

### at 90 μ g/m 3 

### and

on the 21 st 

### at 96 μ g/m 3 

### , respectively. The highest measured PM 10 

### during this episode

was at Fresno on the 20 th 

### with a value of 114 μ g/m 3 

### . Fresno PM 2.5 

### measurement reached a secondary peak on the 28 th 

### at 89 μ g/m 3 

### . This episode was separated into two peaks due to a trough developing over the Great Basin on the 22 nd 

### dispersing some of the PM which had built up over the region.

### 56 According to Hackney, et., al, the 850 MB temperature measured +11 0 

### C and +14 0 

### C on
the 20 th 

### and 28 th 

### , respectively, were representative of an PM episode occurring, whereas, the 500 MB heights of 576 and 572 dm, were indicative of a weak PM episode. During this episode, the state standard was exceeded.

This episode was characterized by a mean mid-tropospheric ridge positioned along the West Coast, with brief drop in the PM measurements on the 29 th 

### and 30 th 

### , when a dry, front passed to the north of the area dropping to PM 2.5 

### measurements at Fresno to 35

μ g/m 3 

### on the 30 th 

### and Bakersfield to 22 μ g/m 3 

### on the 29 th



### .

The ridge began to breakdown late on the 7 th 

### , bringing decreasing stability, better dispersion, and lowering PM concentrations. A series of weak disturbances traversed the region from the 7 th 

### through the 15 th 

### , bringing very light precipitation to Fresno (total = 0.07 inches), increased boundary layer flow and mixing depths, which brought an end to the episode #4.

Episode #5: Saturday, December 16 –Friday, January 12

Episode #5 began on the 16 th 

### and was marked by the West Coast ridge building into California, resulting in lowering boundary layer mixing heights and increasing stability. PM region-wide uniformly increased with 500 MB heights and stability, with a minor intra-episode peak, with PM 10 

### measurement at Fresno of 110 μ g/m 3 

### and PM 2.5 

### measurement at Bakersfield Residential of 58 μ g/m 3 

### , occurring on the 20 th 

### . A weak upper level disturbance briefly broke down the ridge on the 24 th 

### resulting in slightly

lower PM 2.5 

### measurements in Fresno at 49 μ g/m 3 

### and Bakersfield 40 μ g/m 3 

### . After this weak trough passage, the ridge rebuilt in earnest and moderate stability and low mixing heights continued through the end of the episode on January 7 th



### .

During this episode the maximum PM measurements of the CRPAQS period were observed. The general synoptic pattern during this episode was strong high pressure aloft positioned along the West Coast providing a general area of subsidence and stable weather over the region, with an accompanying strong surface high located over Idaho. With high pressure over the Intermountain Region and lower pressures over the eastern Pacific, moderate offshore flow developed. Typically with this type of flow pattern, the normal nocturnal inversion at the surface is reinforced with a subsidence inversion aloft, created by adiabatic warming off the Sierra’s and general subsidence from the ridge.

The peak measurements of the fifth episode were recorded on the 1 st 

### and 7 th 

### with PM 10 

### measurements at Fresno of 193 μ g/m 3 

### (1 st 

### ) and 141 μ g/m 3 

### (7 th 

### ). PM 2.5 

### measurements at
Fresno of 148 μ g/m 3 

### (1 st 

### ) and 101 μ g/m 3 

### (7 th 

### ) and Bakersfield Residential at 133 μ g/m 3 

### (1 st 

### ) were also recorded. These high PM values corresponded with the highest 850 MB stability (+13.4 C at Oakland) measured during the CRPAQS period, which occurred
on the 2 nd 

### . The 850 MB temperature was very warm during this episode. At Oakland at 12Z, the 850 MB temperature was +13 0 

### C. This is representative of a strong PM episode. The 500 MB height was not indicative of a strong episode. At 574 dm, the value was not conducive to a significant PM episode. The combination of weak offshore

### 57 flow and mid-tropospheric stability, elevated the PM readings experienced across
central California.

A significant trough moved into the region on the 8 th 

### , with accompanying rainfall in
Fresno of 0.31 inches and Bakersfield of 0.29 inches. A series of disturbances within the trough traversed the region from the 8 th 

### to the 12 th 

### adequately dispersing the PM that had built up over the region during the episode and lowered PM 2.5 

### measurements into the upper teens by the 10 th 

### in both Fresno and Bakersfield.

Episode 6: Saturday, January 13 –Saturday, January 27

High pressure and increasing subsidence once again moved into the region on the 13 th 

### bringing increasing PM levels and leading to the beginning of the episode #6. This episode was characterized by ridging through the 17 th 

### , resulting in building PM 2.5 

### values

into the lower 60’s μ g/m 3 

### range. Shortly thereafter, more pronounced ridging and decreasing dispersion occurred on the 18 th 

### , when 500 MB heights climbed to near 578 dm with an 850 MB stability indices of +7 ° C (850 MB temperature of +7 0 

### C). The 500 MB height was conducive of an episode occurring, but the 850 temperature was not conducive of an episode. This peak in meteorological parameters corresponded with the highest recorded PM 10 

### measurement of the episode at Fresno at 104 μ g/m 3 

### on the
19 th



### .

PM 2.5 

### peaked at Fresno on the 21 st 

### with a measurement of 103 μ g/m 3 

### and also in
Bakersfield Residential on the 22 nd 

### at 103 μ g/m 3 

### . The southward progression of the peak PM 2.5 

### values can be accounted for by the pre-frontal / trough stability that progressively moved down-valley with the approach of the next system from the eastern
Pacific on the 23 rd



### .

A series of disturbances embedded within the trough moved through the region from the
23 rd 

### to the 27 th 

### , with adequate boundary layer mixing heights, moderate instability, and moderate southeasterly flow, dispersing PM levels into the low teens. From the 23 rd 

### to
the 25 th 

### , a series of strong cold frontal systems brought 1.19 inches of rainfall at Fresno, bringing an end to the 6 th 

### episode. The highest recorded rainfall during the trough passage occurred on 0.85 inches on the 24 th



### .

Episode 7: Sunday, January 28 –Saturday, February 3

The final (7 th 

### ) episode of CRPAQS began on the 28 th 

### , when strong high pressure built along the West Coast. Light boundary layer flow and increasing 850 MB stability
resulted in PM 2.5 

### levels gradually climbing into the early part of February. PM 2.5 

### measurements of 73 μ g/m 3 

### in Fresno on the 3 rd 

### and 92 μ g/m 3 

### in Bakersfield on the 4 th 

### marked the buildup that occurred during this episode.

### 58 

## 12.0 DISPERSION METEOROLOGY FOR THE FALL 2000 AND
WINTER 2001 CALIFORNIA REGIONAL PM 10 

## /PM 2.5 

## AIR QUALITY
STUDY EPISODE

During the Fall 2000 and Winter 2001 episode, strong high pressure at the surface and aloft resulted in limited morning and afternoon mixing and light offshore wind flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode. The California Regional Particulate Air Quality Study (CRPAQS) fall and winter measurements can be divided into seven distinct events. These events, characterized by limited atmospheric dispersion, were separated by vigorous trough passages. Analysis of synoptic patterns shows that once a particulate period begins, a deep trough must traverse the region at both the upper levels of the atmosphere and at the surface as a cold frontal boundary in order to significantly decrease particulate matter (PM) concentrations. These types of troughs are normally associated with strong vertical mixing, moderate to high boundary layer mixing heights, precipitation, and wind speed and directional sheer within the boundary layer.

The meteorological analysis for CRPAQS utilized synoptic analyses, precipitation patterns, and atmospheric stability parameters to determine episode strength and periodicity. Analysis of PM 2.5 

### /PM 10 

### ratios and nitrate levels reveal that when the overnight minimum temperature decreased to below 40 degrees Fahrenheit, coupled with significant warming aloft, fine particulate levels climbed. When prolonged periods of these conditions occurred, PM 2.5 

### levels climbed above the National Ambient Air Quality Standards (NAAQS). In even stronger more persistent stability regimes, PM 10 

### exceeded the NAAQS. Figure 31 shows precipitation, PM 2.5 

### , PM 10 

### , and stability parameters for the CRPAQS period at the Fresno-1 st 

### site. General patterns in these parameters were also evident at other sites. Precipitation influenced PM concentrations during CRPAQS. For the CRPAQS episode, when a frontal system was strong enough to produce precipitation of 0.10 inch or more of liquid water, 24 hour averaged PM 2.5 

### concentrations dropped to below 15 μ g/m 3 

### . Seven distinct events were identified when particulate levels lowered to near background levels.

Each event was marked by limited mixing heights with strong inversions of approximately 500 feet for 18 or more hours of the day. Maximum mixing depths of highest PM 2.5 

### concentration days ranged between 1,500 to 2,500 feet. Moisture availability from recent rainfall and minimal solar insulation, led to prime nitrate and sulfate forming conditions. Typically, light fog, with humidity measurements between 85 – 100% were needed in order to maximize particulate forming potential. The higher the humidity, the heavier and wetter the fog, resulted in the removal of particulates by wet deposition.

Within these seven distinct measurement periods, a violation of the Federal 24 hour
PM 2.5 

### standard of 65 micrograms/cubic meter were recorded during the 4 th 

### , 5 th 

### , 6 th 

### , and

7 th 

### events at various locations across the San Joaquin Valley. The following analysis will investigate the meteorological and dispersion conditions surrounding each event.

### 59 Figure 31: Fresno-1st Fall 2000 and Winter 2001 Episode

0 20 40 60 80 100 120 140 160 180 20010/1/200010/8/200010/15/200010/22/200010/29/200011/5/200011/12/200011/19/200011/26/200012/3/200012/10/200012/17/200012/24/200012/31/20001/7/20011/14/20011/21/20011/28/2001PM10, PM 2.5(Micrograms/cubic^3) andprecipitation (inches)

-10 -5 0 5 10 15 20T850 Stability (C) PM10 (micrograms per cubic meter) Precipitation*100 (inches) PM 2.5 (micrograms/cubic meter) Oakland T850-T(FAT MIN) (Celsius)



### 12 3 7 5 4 6 Start of Episode



### Event #4: November 16 through December 14, 2000

Meteorologically, dispersion worsened and particulate formation conditions became
more favorable from November 16 th 

### to December 10 th 

### . As is evident in Figure 31

, event #4 lasted about 28 days and was marked by two main PM 2.5 

### peaks, which exceeded the Federal Standard. After the passage of a weak cold front on November 14, 2000, which brought a trace to a few hundredths of an inch of precipitation across the region, moisture became available for atmospheric chemistry reactions. Humidity measurements of 90 – 100 % in the morning across the Valley Floor showed a moist atmosphere, with light fog and haze being reported on measured high PM 2.5 

### days. These cool damp mornings and strong stability favored the formation of nitrates and sulfates. It does not appear that the water content of the atmosphere was high enough to create deposition of particles that exceeded formation.

Synoptically during the first part of event #4, the eastern Pacific high built over the
Pacific Northwest on November 17 th 

### then expanded southward on the 18 th 

### , bringing increasing stability and poor dispersion conditions through November 30 th 

### . From
November 17 th 

### through the 30 th 

### , the high strengthened and intensified on November
19 th 

### through the 20 th 

### and once again on November 24 th 

### through the 28 th 

### , further tightening the lid and trapping the pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place aloft and maximum high temperatures in the upper 50’s to low
60’s on the 19 th 

### and 20 th 

### , and upper 40’s to low 50’s on the 24 th 

### through the 27 th 

### , the afternoon hours were marked by limiting mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion

### 60 during a majority of the day (18 or more hours) on days when the fine particulates climbed above the standard. During the afternoon hours, there were high mixing depths (maximum mixing depth of 1,500 to 2,500 feet), but the bulk of the day had limited mixing. Maximum and minimum temperatures from November 19 th 

### through the 27 th



### , were below normal, indicating a potential for increasing residential wood burning emission activity, and nitrate forming reactions.

Light fog and haze were reported at the Valley surface during the early morning hours of
November 19 th 

### through the 27 th 

### , resulting in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the early morning fog and haze, low sun angle, and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Light fog would be indicative of moderate atmospheric water content that contribute to the formation of ammonium nitrate. Heavier fogs result in the removal of particulates by wet deposition.

Meteorological data during the first part of event #4 showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions across the San Joaquin Valley accumulated resulting in the exceedance of the 24-hour PM 2.5 

### standard
at Fresno-1 st 

### on November 19 th 

### , Modesto 14 th 

### , Clovis-Villa, Fresno-1 st 

### , Visalia-Church, Corcoran-Patterson, Oildale, Bakersfield-Golden and California on November 20 th



### , Bakersfield-California on November 21 st 

### , Fresno-1 st 

### on November 24 th 

### , BakersfieldCalifornia on November 25 th 

### , Bakersfield-Golden and California on November 26 th



### , Bakersfield-California on November 27 th 

### , and Clovis-Villa, on November 28 th



### .

A dissipating cold front moved over the San Joaquin Valley on the 29 th 

### , bringing an end to the first part of event #4 that lasted from November 16 th 

### through the 30 th 

### . The disturbance brought moderate dispersion conditions across the Valley, allowing for pollutants to lower into the 25 to 30 micrograms per cubic meter range

, but was not significant enough to drop PM 2.5 

### levels to background.

High pressure rebuilt over the region on December 1 st 

### , leading to the second part of event #4. Meteorologically, dispersion rapidly deteriorated and particulate formation
conditions became more favorable on December 2 nd 

### . Humidity measurements of 90 – 100 % in the morning across the Valley Floor showed a continued moist atmosphere, with light fog and haze being reported on measured high PM 2.5 

### days. These cool damp mornings and strong stability favored the formation of nitrates and sulfates.

Synoptically during the second part of event #4, the eastern Pacific high built along the
West Coast on the 1 st 

### then expanded eastward on the 2 nd 

### , bringing increasing stability and poor dispersion conditions through the end of event # 4 on December 12. During this period, the high strengthened and intensified on December 2 nd 

### and once again on
December 8 th 

### through the 10 th 

### , further tightening the lid trapping the pollutants within the San Joaquin Valley boundary layer.

### 61 With a strong lid in place aloft and maximum high temperatures in the upper 40’s to low 50’s, the afternoon hours of December 2 nd 

### through the 8 th 

### were marked by limiting mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion during a majority of the day (18 or more hours) on days when the fine particulates climbed above the standard. During the afternoon hours, there were high mixing depths (maximum mixing depth of 1,000 to 2,500 feet), but the bulk of the day had limited mixing.

Maximum and minimum temperatures from December 2 nd 

### through the 5 th 

### were slightly
below normal and from December 7 th 

### to the 12 th 

### were above normal. Light fog and haze were reported at the Valley surface during the early morning hours of December

2 nd 

### through the 10 th 

### , resulting in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the early morning fog and haze, low sun angle, and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Light fog would be indicated of moderate water content’s that contribute to the formation of ammonium nitrate. Heavier fogs result in the removal of particulates by wet deposition.

Meteorological data during the second part of event #4 showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Daily filter measurements at Bakersfield-California and Fresno-1 st 

### indicated
that between December 3 rd 

### and 4 th 

### , PM 2.5 

### levels dropped below the PM 2.5 

### standard in response to heavy fog, which lead to the removal of particulates by wet deposition. However, on the 7 th 

### and 8 th 

### the fog lifted to low clouds across the San Joaquin Valley causing both primary and secondary pollutants from local emissions across the region to accumulate resulting in the exceedance of the 24-hour PM 2.5 

### standard at various monitoring sites from December 5 th 

### through the 10 th 

### . An exceedance of the 24-hour
PM 2.5 

### standard were measured at Bakersfield California on December 5 th 

### through the
10 th 

### , Modesto-14 th 

### , Clovis-Villa, Fresno 1 st 

### , Visalia, Corcoran, Oildale, BakersfieldGolden, and Edison, on December 8 th 

### , and Fresno 1 st 

### on December 9 th 

### . A moderate cold front traversed over the San Joaquin Valley on December 11 th 

### bringing upwards to 0.05 to 0.10 of an inch of precipitation across different parts of the District. This frontal passage brought moderate dispersion conditions across the Valley, allowing for pollutants to lower to near background levels bringing an end to event #4.

Event #5: December 15, 2000 through January 11, 2001

Meteorologically, dispersion worsened and particulate formation conditions strengthened from December 10 th 

### to January 7 th 

### . As is shown in Figure 31 , event #5 lasted about 27 days and was marked by a gradual buildup of PM 2.5 

### that lead to multiple days the Federal PM 2.5 

### Standard was exceeded. During event #5, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore wind flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode.

### 62 After the passage of a cold front on December 11, 2000, which brought a few hundredths of an inch of precipitation to the region, moisture became available for atmospheric chemistry reactions. Humidity measurements of 90 – 100 % in the morning across the Valley Floor showed a moist atmosphere, with light fog and haze being reported on the exceedance days. These cool damp mornings and strong stability favored the formation of nitrates and sulfates.

Synoptically during event #5, the eastern Pacific high built over the San Joaquin Valley on December 12, 2000 and dominated the region’s weather through January 7, 2001. The event was divided into two periods from December 15 through December 24, 2000 and December 24, 2000 to January 11, 2001. A trough moved into northern California on December 24, allowing for slightly better dispersion conditions and a decrease in fine particulate levels across the San Joaquin Valley.

High pressure gradually intensified over the San Joaquin Valley between December 12 th 

### through the 20 th 

### , leading to PM 2.5 

### levels exceeding the National Ambient Air Quality
Standards on December 20 th 

### at Fresno-1 st 

### . However, by December 22 a weak trough moved into northern California providing improving dispersion conditions across the San Joaquin Valley and lowering fine particulate measurements to below the National and California Ambient Air Quality Standards.

By December 25 th 

### , the combination of increased local emissions due to the Christmas and New Year Holiday’s and intensifying stability aloft initiated an eleven day stretch were numerous sites across the San Joaquin Valley exceeded the PM 2.5 

### Standard. These violations began in the urban areas of Fresno, Modesto, and Bakersfield and spread regionally into the rural sections by the end of the episode on January 7. The meteorology surrounding this event were classified as an intense high dominating central California’s air quality, leading to strong stability and light wind flow.

With a strong lid in place aloft and maximum high temperatures in the upper 50’s to low 60’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion for 19 hours on January 1 st 

### , breaking out after 4:00 P.M and reforming shortly after 7:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 1,000 feet), but the bulk of the day had limited mixing.

Maximum and minimum temperatures for the exceedance day were slightly above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog was reported at the Valley surface during the early morning hours of January 1 st 

### , resulting in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the early morning fog, low sun angle, and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Light fog would be indicative of moderate water content’s that favor the formation of ammonium nitrate. Heavier fogs result in the removal or particulates by wet deposition. Chemical composition and meteorological

### 63 data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants.

Meteorological conditions remained extremely stable between January 1 st 

### through the

4 th 

### , leading to elevated fine particulate conditions continuing across the San Joaquin Valley. Without a significant weather disturbance moving through the area to scour out the particulates, PM 2.5 

### concentrations continued to climb and exceeded the NAAQS at multiple urban and rural monitoring sites on January 4 th



### .

With a strong lid in place aloft and maximum high temperatures in the low 60’s, the afternoon hours on January 4 th 

### , were marked by limited mixing, resulting in increasing particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion for 20 hours on January 4 th 

### . During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing.

Maximum temperatures for this exceedance day were above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog reported at the Valley surface during the early morning hours, resulted in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the low sun angle and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. The following day, January 5 th 

### , PM 2.5 

### measurements recorded the highest levels during event #5.

Between January 5 th 

### and January 7 th 

### , meteorological conditions began to slowly improve leading to slightly lower but continued elevated particulate conditions across the San Joaquin Valley. Without a significant weather disturbance moving through the area to scour out the fine particulates, PM 2.5 

### and PM 10 

### concentrations continued to remain high and exceeded the Federal Standard, ( Table 20 and Figure 32, 33, 34, and
35 ). Humidity measurements of 85 – 100 % on the morning of January 7 th 

### , across the Valley Floor showed a relatively moist atmosphere, with light fog and haze being reported. The cool damp mornings and strong stability favored the formation of nitrates and sulfates. Synoptically, the eastern Pacific high began to slowly weaken and move into the Intermountain Region on January 7, 2001, slightly weakening the lid over the San Joaquin Valley.

On January 7 th 

### a moderately strong lid was in place aloft and maximum high temperatures were in the mid 60’s. The afternoon hours were marked by limited mixing, resulting in elevated particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion for 16 hours on January 7 th 

### . During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing. Maximum temperatures for this exceedance day were above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather.

### 64 Light fog reported at the Valley surface during the early morning hours, resulted in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the low sun angle and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulting in minimal transport and dispersion of pollutants. Event # 5 came to an end when a significant trough from the eastern Pacific moved through the region on January
8 th 

### , bringing superior dispersion conditions and measurable amounts of precipitation.

Table 20 PM 10 

### Chemical Composition Data 1 

### for January 1, 4 and 7, 2001 at selected
exceedance sites. Data Collected as part of the Routine and CRPAQS Networks.

Concentrations (μg/m 3 ) Percent of PM 10 Mass

SITE NAME Date PM 10 PM 2.5 Nitrate/
Sulfate TC Geological PM 2.5 Nitrate/
Sulfate TC Geological
Bakersfield-California 1/1/01 186 133 100 33 71 54 18
Bakersfield-California 1/4/01 190 127 98 30 67 51 16
Bakersfield-California 1/7/01 159 119 81 24 75 51 15
Bakersfield-Golden 1/1/01 205
Bakersfield-Golden 1/4/01 208 106 38 47 51 18 23
Bakersfield-Golden 1/7/01 174
Clovis-N. Villa 1/1/01 155 130 77 84 50
Corcoran-Patterson 1/7/01 165 121 93 73 56
Fresno-1st Street 1/1/01 193 148 76 51 7 77 40 26 4
Fresno Drummond 1/1/01 186
Fresno Drummond 1/4/01 159 58 52 29 37 33 18
Hanford-S. Irwin 1/7/01 185 105 57

Modesto-14 th St. 1/7/01 158 136 88 26 86 56 16
Oildale-Manor 1/1/01 158 141 96 89 61
Oildale-Manor 1/4/01 195 119 28 43 61 14 22

1 The following fonts were used in the table to distinguish data sources:

• Regular font for routine data (FRM mass and chemical composition)

• Underlined font for mass collected using dichotomous sampler Italics font for CRPAQS data

### 65 Figure 32: Fresno-1st (Coarse) and (PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200

1 2/

1 6/ 2 000

1 2/

1 8/ 2 000

1 2/ 2 0/ 2 000

1 2/ 2 2/ 2 000

1 2/ 2 4/ 2 000

1 2/ 2 6/ 2 000

1 2/ 2 8/ 2 000

1 2/ 3 0/ 2 000

1 /1 / 20

0 1 1 /3 / 20

0 1 1 /5 / 20

0 1 1 /7 / 20

0 1 1 /9 / 20

0 1Particulate Matter (micrograms/cubic meter) FAT-1st Coarse

FAT-1st PM2.5

FAT-1st PM2.5

Figure 33: Bakersfield California (Coarse) and (PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200

1 2/ 1 6/ 20

0 0 1 2/ 1 7/ 20

0 0 1 2/ 1 8/ 20

0 0 1 2/ 1 9/ 20

0 0 1 2/ 2 0/ 20

0 0 1 2/ 2 1/ 20

0 0 1 2/ 2 2/ 20

0 0 1 2/ 2 3/ 20

0 0 1 2/ 2 4/ 20

0 0 1 2/ 2 5/ 20

0 0 1 2/ 2 6/ 20

0 0 1 2/ 2 7/ 20

0 0 1 2/ 2 8/ 20

0 0 1 2/ 2 9/ 20

0 0 1 2/ 3 0/ 20

0 0 1 2/ 3 1/ 20

0 0 1 /1 /2 0 01 1 /2 /2 0 01 1 /3 /2 0 01 1 /4 /2 0 01 1 /5 /2 0 01 1 /6 /2 0 01 1 /7 /2 0 01 1 /8 /2 0 01 1 /9 /2 0 01Particulate Matter (micrograms/cubic meter) BFL-CAL Coarse

BFL-CAL PM2.5

BFL-CAL PM2.5

Figure 34: Bakersfield Golden (Coarse), (PM10), and (PM2.5) and Bakersfield California (PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200 220

1 2/ 16

/2 00

0 1 2/ 17

/2 00

0 1 2/ 18

/2 00

0 1 2/ 19

/2 00

0 1 2/ 20

/2 00

0 1 2/ 21

/2 00

0 1 2/ 22

/2 00

0 1 2/ 23

/2 00

0 1 2/ 24

/2 00

0 1 2/ 25

/2 00

0 1 2/ 26

/2 00

0 1 2/ 27

/2 00

0 1 2/ 28

/2 00

0 1 2/ 29

/2 00

0 1 2/ 30

/2 00

0 1 2/ 31

/2 00

0 1 /1 / 200

1 1 /2 / 200

1 1 /3 / 200

1 1 /4 / 200

1 1 /5 / 200

1 1 /6 / 200

1 1 /7 / 200

1 1 /8 / 200

1 1 /9 / 200

1Particulate Matter (micrograms/cubic meter) BFL-Gold PM10

BFL-Gold Coarse

BFL-Gold PM2.5

BFL-CAL PM2.5

### 66 Figure 35: Hanford, Oildale, and Modesto (PM10) and Fresno-1st & Bakersfield-California(PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200

1 2/ 16

/2 00

0 1 2/ 17

/2 00

0 1 2/ 18

/2 00

0 1 2/ 19

/2 00

0 1 2/ 20

/2 00

0 1 2/ 21

/2 00

0 1 2/ 22

/2 00

0 1 2/ 23

/2 00

0 1 2/ 24

/2 00

0 1 2/ 25

/2 00

0 1 2/ 26

/2 00

0 1 2/ 27

/2 00

0 1 2/ 28

/2 00

0 1 2/ 29

/2 00

0 1 2/ 30

/2 00

0 1 2/ 31

/2 00

0 1 /1 / 200

1 1 /2 / 200

1 1 /3 / 200

1 1 /4 / 200

1 1 /5 / 200

1 1 /6 / 200

1 1 /7 / 200

1 1 /8 / 200

1 1 /9 / 200

1Particulate Matter (micrograms/cubic meter) Hnf PM10

Oil PM10

Mod PM10

FAT PM2.5

BFL-CA PM2.5



### Event #6: January 12, 2001 through January 24, 2001

Meteorologically, dispersion worsened and particulate formation conditions became more favorable from January 14 th 

### to January 23 rd 

### . As is shown in Figure 31 , event #6 lasted about 12 days and was marked by a gradual buildup of PM 2.5 

### that lead to multiple days the Federal PM 2.5 

### Standard was exceeded. After the passage of a trough on January 13 th 

### , which brought measurable precipitation across the region, moisture became available for atmospheric chemistry reactions. Humidity measurements of 90 – 100 % in the morning across the Valley Floor showed a moist atmosphere, with light fog and haze being reported on measured high PM 2.5 

### days. These cool damp mornings and strong stability favored the formation of nitrates and sulfates.

Synoptically during event #6, the eastern Pacific high built over the Pacific Northwest on January 15 th 

### then expanded southward on the 18 th 

### , bringing increasing stability and poor dispersion conditions through January 22 nd 

### . During this period, the high strengthened and intensified on January 18 th 

### , further tightening the lid and trapping the pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place aloft and maximum high temperatures in the low 50’s on the
18 th 

### and 19 th 

### , and low 60’s on the 20 th 

### through the 22 nd 

### , the afternoon hours were marked by limiting mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion during a majority of the day (20 or more hours) on days when the fine particulates climbed above the Standard. During the afternoon hours, there were high mixing depths (maximum mixing depth of 1,500 to 2,500 feet), but the bulk of the day had limited mixing. Maximum and minimum temperatures from January 18 th 

### through the 21 st 

### , were below normal, indicating a potential for increase residential wood burning emission activity, and nitrate forming
reactions.

### 67 Light fog and haze were reported at the Valley surface during the early morning hours of January 18 th 

### through the 22 nd 

### , resulting in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the early morning fog and haze, low sun angle, and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Light fog would be indicated of
moderate water content’s that contribute to the formation of ammonium nitrate.

Meteorological data showed during event #6 limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions across the San Joaquin Valley accumulated resulting in the exceedance of the 24-hour PM 2.5 

### standard at Fresno-1 st 

### on January 16 th 

### through January 22 nd 

### , Visalia-Church, Corcoran-Patterson, Oildale-Manor, Bakersfield-Golden, Bakersfield-California, Angiola, and Edison, on January 19 th



### , Modesto-14 th 

### , Angiola, and Bakersfield-Californian on January 20 th 

### , Angiola and Bakersfield-California on January 21 st 

### , Angiola, Bakersfield-California, CorcoranPatterson, Visalia-Church, and Bakersfield-Golden on January 22 nd 

### . A vigorous cold front moved over the San Joaquin Valley on January 23 rd 

### , bringing and end to event # 6 that lasted from January 12 th 

### through January 24 th 

### . This disturbance brought superior dispersion conditions across the Valley, allowing pollutants to lower into the 5 to 11 micrograms per cubic meter range (background levels).

Event #7: January 25 th 

### through February 7 th 

### , 2003

A series of Pacific storms moved through the region from January 25 th 

### through January
30 th 

### , resulting in superior dispersion conditions over the San Joaquin Valley, with PM 2.5 

### concentrations nearing background levels. As is evident in Figure 31 , event #7 lasted about 13 days and was marked by a gradual buildup of PM 2.5 

### that lead to multiple days
the Federal PM 2.5 

### Standard was exceeded. High pressure rebuilt over the region on January 31 st 

### , leading to building particulate concentrations over the central and southern portions of the District. Meteorologically, dispersion rapidly deteriorated and particulate formation conditions became more favorable on February 1 st 

### . Humidity measurements of 90 – 100 % in the morning across the Valley Floor showed a continued moist atmosphere, with light fog and haze being reported on measured high
PM 2.5 

### days. These cool damp mornings and strong stability favored the formation of
nitrates and sulfates.

Synoptically during event #7, the eastern Pacific high built along the West Coast on February 1 st 

### then expanded eastward on the 2 nd 

### , bringing strengthening stability and poor dispersion conditions through the end of event # 7 on February 6 th 

### . During this period, the high strengthened and intensified on February 1 st 

### , further tightening the lid trapping the pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place aloft and maximum high temperatures in the mid to upper 60’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion

### 68 during a majority of the day (18 or more hours) on days when the fine particulates climbed above the NAAQS. During the afternoon hours, there were high mixing depths (maximum mixing depth of 1,000 to 2,500 feet), but the bulk of the day had limited mixing. Maximum and minimum temperatures from February 3 rd 

### through the 5 th 

### were above normal. Light fog and haze were reported at the Valley surface during the early morning hours of February 3 rd 

### through the 5 th 

### , resulting in slightly lower solar radiation
intensities.

Along with lower solar radiation intensities due to the early morning fog and haze, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Light fog would be indicated of moderate water content’s that contribute to the formation of ammonium nitrate. Meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. An exceedance of the 24-hour PM 2.5 

### standard were measured at Bakersfield California on February 3 rd 

### through the 5 th 

### , Bakersfield Golden on February 3 rd 

### and 6 th



### , Corcoran on February 3 rd 

### , Fresno 1 st 

### on February 3 rd 

### and 4 th 

### , and Clovis on February
3 rd 

### . A cold front traversed over the San Joaquin Valley late in the afternoon on February 6 th 

### , producing trace amounts of precipitation across different parts of the District. This frontal passage brought weak to moderate dispersion conditions across the Valley, lowering PM2.5 levels to below the NAAQS. A vigorous upper level system moved through the region on the 7 th 

### , allowing for pollutants to lower to near background levels, bringing an end to event #7.

### 69 

## 13.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND
METEOROLOGY DURING THE JANUARY 2001 EPISODE

The January 2001 particulate episode was characterized by a prolonged period (three and a half weeks) of strong stability and light wind flow, which resulted in poor atmospheric dispersion conditions across the San Joaquin Valley. Coarse and fine particulates accumulated during the period leading to three separate days exceeding the National Ambient Air Quality Standards (NAAQS). These exceedances occurred on January 1, 4, and 7, 2001 and were measured by Federal Reference Monitoring (FRM) sites and MiniVol Samplers, which were part of the California Regional Particulate Air Quality Study (CRPAQS). The CRPAQS exceedances are not considered for compliance with the Federal Standards, but are used in the discussion to provide context to the episode. PM 10 

### and PM 2.5 

### concentrations, chemical composition, and meteorological data around January 1, 4, and 7, 2001 were evaluated and analyzed to identify the characteristics and uniqueness of the exceedances at the FRM and CRPAQS PM 10 

### monitoring sites.

PM 10 

### and PM 2.5 

### Mass Concentrations

Daily PM 2.5 

### sampling and meteorological conditions suggest that PM 10 

### exceedances began on December 31, 2000 and continued through January 7, 2001 at various monitoring sites across the San Joaquin Valley. PM 2.5 

### exceedances began a few days earlier on December 25 and 26, 2000, when real-time monitors captured readings
above the Federal Standard of 65 μ g/m 3 

### . Although PM 10 

### sampling is not conducted daily, information from more frequent PM 2.5 

### sampling combined with an assessment of changes in the meteorological conditions suggest that the highest PM 10 

### concentrations were not captured on the sampled days. The highest PM 10 

### concentrations may have occurred on January 1 st 

### and January 6 th 

### , when Fresno 1 st 

### measured a peak PM 2.5 

### concentration of 148 and 129 μ g/m 3 

### , respectively. PM 10 

### samples were available on January 1 st 

### . However, no PM 10 

### data was available on January 6 th 

### . Particulate material concentrations were dominated by fine particulates (PM 2.5 

### ) of ammonia nitrate and sulfate and were most prevalent across the entire San Joaquin Valley.

Although dispersion was poor, given the length of the episode and the large contributions from secondary components, there was an underlying regional component to this episode as it progressed through January 7 th 

### . Local carbon and geologic contributions added to this regional component and influenced site to site concentration variations. As the episode continued, PM and precursors became more homogeneous across the region. This resulted in PM 2.5 

### concentrations at rural sites lagging those of urban sites, and rural concentrations continued to build throughout the episode.

The FRM sites which exceeded the Federal PM 10 

### standard on January 1, 2001, were
Clovis-Villa 155 μ g/m 3 

### , Fresno-1 st 

### 193 μ g/m 3 

### , Fresno-Drummond 186 μ g/m 3



### , Bakersfield-California 186 μ g/m 3 

### , Bakersfield-Golden 205 μ g/m 3 

### , and Oildale-Manor 158

μ g/m 3 

### ( Figure 36, 37, 38, and 39 and Table 21 ). PM 10 

### at other Valley locations were elevated but not over the Standard. For example, Stockton-Wagner and Visalia-Church

### 70 recorded 119 μ g/m 3 

### and 143 μ g/m 3 

### , respectively. The size fraction data on January 1 st 

### across the Valley indicated that most of the PM 10 

### mass was in the PM 2.5 

### fraction, with an average PM 2.5 

### /PM 10 

### mass ratio greater than 0.7. This was further supported by the high PM 2.5 

### concentrations that reached 148 μ g/m 3 

### at Fresno-First and 133 μ g/m 3 

### at Bakersfield-Golden ( Figure 36 and 38 ).

Stagnation conditions continued through January 4, 2001, when three MiniVol Samplers, which were part of the California Regional Particulate Air Quality Study (CRPAQS) and one federal reference monitor (FRM) registered exceedances of the Federal Standard. The CRPAQS monitors measured at Fresno-Drummond, 159 μ g/m 3



### , at Bakersfield-Golden, 208 μ g/m 3 

### , and at Oildale-Manor, 195 μ g/m 3 

### ( Figure 38 and 39

and Table 21 ). The FRM PM 10 

### concentration at Bakersfield-California was 190 μ g/m 3 

### ( Figure 37 and Table 21 ). The size fraction data across the Valley on January 4 th



### indicated that most of the PM 10 

### was in the PM 2.5 

### fraction, with an average PM 2.5 

### /PM 10 

### mass ratio greater than 0.8. This was further supported by the high PM 2.5 

### concentrations that reached 106 μ g/m 3 

### at Fresno-First and 127 μ g/m 3 

### at BakersfieldCalifornia ( Figure 36, 38, & 39 ).

Poor dispersion conditions continued through January 7, 2001, when five FRM monitors registered exceedances of the Federal Standard. The FRM sites, which exceeded the

Federal PM 10 

### Standard on January 7 th 

### , were Bakersfield-California, 159 μ g/m 3



### , Bakersfield-Golden, 174 μ g/m 3 

### , Corcoran-Patterson, 165 μ g/m 3 

### , Hanford-Irwin, 185

μ g/m 3 

### , and Modesto-14 th 

### , 158 μ g/m 3 

### ( Figure 37, 38, and 39 and Table 21 ). The size fraction data across the Valley on January 7, 2001 indicated that most of the PM 10 

### was in the PM 2.5 

### fraction, with an average PM 2.5 

### /PM 10 

### mass ratio greater than 0.75. This was further supported by the high PM 2.5 

### concentrations that reached 101 μ g/m 3 

### at
Fresno-First and 119 μ g/m 3 

### at Bakersfield-California ( Figure 36 & 37 ). Chemical composition data was than analyzed to identify the characteristics and uniqueness of the exceedances at the FRM and CRPAQS PM 10 

### monitoring sites.

Figure 36: Fresno-1st (Coarse) and (PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200

1 2/ 16

/2 00

0 1 2/ 18

/2 00

0 1 2/ 20

/2 00

0 1 2/ 22

/2 00

0 1 2/ 24

/2 00

0 1 2/ 26

/2 00

0 1 2/ 28

/2 00

0 1 2/ 30

/2 00

0 1 /1 / 200

1 1

/3 / 200

1 1

/5 / 200

1 1

/7 / 200

1 1

/9 / 200

1Particulate Matter (micrograms/cubic meter) FAT-1st Coarse

FAT-1st PM2.5

FAT-1st PM2.5

### 71 Table 21 PM 10 

### Chemical Composition Data 1 

### for January 1, 4 and 7, 2001
at selected exceedance sites.

Data collected as part of the Routine and CRPAQS Networks.

Concentrations (μg/m 3 ) Percent of PM 10 Mass

SITE NAME Date PM 10 PM 2.5 Nitrate/
Sulfate TC Geological PM 2.5 Nitrate/
Sulfate TC Geological
Bakersfield-California 1/1/01 186 133 100 33 71 54 18
Bakersfield-California 1/4/01 190 127 98 30 67 51 16
Bakersfield-California 1/7/01 159 119 81 24 75 51 15
Bakersfield-Golden 1/1/01 205
Bakersfield-Golden 1/4/01 208 106 38 47 51 18 23
Bakersfield-Golden 1/7/01 174
Clovis-N Villa 1/1/01 155 130 77 84 50
Corcoran-Patterson 1/7/01 165 121 93 73 56
Fresno-1st Street 1/1/01 193 148 76 51 7 77 40 26 4
Fresno Drummond 1/1/01 186
Fresno Drummond 1/4/01 159 58 52 29 37 33 18
Hanford-S Irwin 1/7/01 185 105 57
Modesto-14th St. 1/7/01 158 136 88 26 86 56 16
Oildale-Manor 1/1/01 158 141 96 89 61
Oildale-Manor 1/4/01 195 119 28 43 61 14 22

1 The following fonts were used in the table to distinguish data sources:

• Regular font for routine data (FRM mass and chemical composition)

• Underlined font for mass collected using dichotomous sampler

• Italics font for CRPAQS data

### 72 Figure 37: Bakersfield California (Coarse) and (PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200

1 2/ 16

/2 00

0 1 2/ 18

/2 00

0 1 2/ 20

/2 00

0 1 2/ 22

/2 00

0 1 2/ 24

/2 00

0 1 2/ 26

/2 00

0 1 2/ 28

/2 00

0 1 2/ 30

/2 00

0 1 /1 / 200

1 1

/3 / 200

1 1

/5 / 200

1 1

/7 / 200

1 1

/9 / 200

1Particulate Matter (micrograms/cubic meter) BFL-CAL Coarse

BFL-CAL PM2.5

BFL-CAL PM2.5

Figure 38: Bakersfield Golden (Coarse), (PM10), and (PM2.5) and Bakersfield California (PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200 220

1 2/ 16

/2 00

0 1 2/ 18

/2 00

0 1 2/ 20

/2 00

0 1 2/ 22

/2 00

0 1 2/ 24

/2 00

0 1 2/ 26

/2 00

0 1 2/ 28

/2 00

0 1 2/ 30

/2 00

0 1 /1 / 200

1 1

/3 / 200

1 1

/5 / 200

1 1

/7 / 200

1 1

/9 / 200

1Particulate Matter (micrograms/cubic meter) BFL-Gold PM10

BFL-Gold Coarse

BFL-Gold PM2.5

BFL-CAL PM2.5

Figure 39: Hanford, Oildale, and Modesto (PM10) and Fresno-1st & Bakersfield-California(PM2.5) January 2001 Episode

0 20 40 60 80 100 120 140 160 180 200

1 2/ 16

/2 00

0 1 2/ 17

/2 00

0 1 2/ 18

/2 00

0 1 2/ 19

/2 00

0 1 2/ 20

/2 00

0 1 2/ 21

/2 00

0 1 2/ 22

/2 00

0 1 2/ 23

/2 00

0 1 2/ 24

/2 00

0 1 2/ 25

/2 00

0 1 2/ 26

/2 00

0 1 2/ 27

/2 00

0 1 2/ 28

/2 00

0 1 2/ 29

/2 00

0 1 2/ 30

/2 00

0 1 2/ 31

/2 00

0 1 /1 / 200

1 1 /2 / 200

1 1 /3 / 200

1 1 /4 / 200

1 1 /5 / 200

1 1 /6 / 200

1 1 /7 / 200

1 1 /8 / 200

1 1 /9 / 200

1Particulate Matter (micrograms/cubic meter) Hnf PM10

Oil PM10

Mod PM10

FAT PM2.5

BFL-CA PM2.5



### Chemical Composition Data

Ammonium nitrate and sulfates increased prior to the exceedance day on January 1, 2001, whereas total carbon and geological remained stable. Chemical composition

### 73 data on January 1, 2001 showed the exceedances were driven by high concentrations of ammonium nitrate and sulfate that comprised of 40 to 60 % of the PM 10 

### mass. The other major chemical components of the samples were 18 to 26 % total carbon and 4 to 20 % geological of the PM 10 

### mass ( Table 21 ). At Fresno-First the concentration of total carbon (26 % of PM 10 

### mass) and coarse material (4 % of PM 10 

### mass) indicated the constituents of the particulate samples on January 1 st 

### may predominantly come from local sources, such as residential wood burning ( Table 21 ). Since December 2000 No Burn Day’s were declared District-wide; consequently, agricultural burning was probably not a contributing source of PM on the exceedance days in January. However, burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Overnight minimum temperatures in the low 30’s on January 1, 4 and 7, 2001 suggested that residential wood burning may have been a significant source of
PM 10 

### . The potential of increased residential wood burning on New Year’s Day, may have led to elevated concentrations of total carbon in the samples.

Local emission source activity and meteorological conditions led to PM 10 

### concentrations at Bakersfield-Golden, Oildale-Manor, and Bakersfield-California climbing between January 1 st 

### and the 4 th 

### . Fresno-Drummond PM 10 

### concentrations lowered during this same period. Because limited mixing and light winds remained over the area, this
decrease in PM 10 

### at the site may have been due to lower emission activity there. Analysis of ammonium nitrates and sulfates indicates that Oildale-Manor and Bakersfield-California registered higher levels compared to non-exceedance locations, indicating potentially that local emissions sources may have impacted these sites. The exceedances at Fresno-Drummond, Oildale-Manor, and Bakersfield-California and Golden on January 4 th 

### , were driven by high concentrations of ammonia nitrate and
sulfate and/or total carbon.

The concentration at Bakersfield-Golden of ammonium nitrate and sulfate (106 μ g/m 3 

### ), total carbon (18 μ g/m 3 

### ), and geological (23 μ g/m 3 

### ), was the highest PM 10 

### mass in the Valley on January 4 th 

### ( Table 21 ). The concentration at Oildale-Manor, BakersfieldCalifornia, Fresno-Drummond, were the second, third and fourth highest PM 10 

### mass in the Valley ( Table 21 ). The constituents of the particulate samples on January 4, 2001 may predominantly come from local sources (residential wood burning and urban / agricultural geologic). The lack of precipitation since December 9 th 

### may have also contributed to the increasing geological component. PM 10 

### and PM 2.5 

### concentrations showed that meteorological conditions led to the pollution buildup. Ammonium nitrate and sulfates, and geological increased prior to the exceedance on January 4, 2001,
whereas total carbon remained stable.

Local emission source activity and meteorology led to PM 10 

### concentrations at HanfordIrwin, Corcoran-Patterson, and Modesto-14 th 

### climbing between January 4 th 

### and the 7 th



### , while PM 10 

### concentrations at Bakersfield-Golden and California lowered. Because dispersion conditions remained poor, local emission activity around Bakersfield may have decreased prior to January 7 th 

### leading to lowering PM 10 

### levels. Both Bakersfield California and Golden measured lower ammonium nitrate and sulfate levels compared
to the 4 th 

### , further indicating that potentially local emission source activity may have

### 74 decreased on the 7 th 

### at these sites. Analysis of ammonium nitrates and sulfates
indicates that Modesto-14 th 

### , Hanford-Irwin, Corcoran-Patterson, registered higher levels compared to non-exceedance locations, indicating potentially that local emissions sources may have impacted these sites.

The exceedances at Bakersfield-California, Bakersfield-Golden, Corcoran-Patterson, Hanford-Irwin, and Modesto-14 th 

### were driven by high concentrations of ammonia nitrate and sulfate and/or total carbon, which remained high and elevated between January 4 th 

### and January 7 th 

### . Ammonium nitrate and sulfates, and total carbon increased prior to the exceedance on January 7, 2001 at Modesto-14 th 

### , Corcoran-Patterson, and HanfordIrwin whereas at Bakersfield-Golden and California ammonium nitrate and sulfates, and total carbon slightly decreased. The concentration at Hanford-Irwin of ammonium nitrate and sulfate (105 μ g/m 3 

### ) and no total carbon and geological measurements, had the highest PM 10 

### mass in the Valley on January 7 th 

### ( Table 21 ). The concentration at Bakersfield-Golden, Corcoran-Patterson, Bakersfield-California, Modesto-14th, had the second, third, fourth, and fifth highest PM 10 

### mass in the Valley ( Table 21 ). The constituents of the particulate samples on January 7, 2001 may predominantly come from local emission sources (residential wood burning and urban / agricultural geologic).

Dispersion Meteorology

During the January 2001 episode, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore wind flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode. Meteorologically, dispersion worsened and particulate formation conditions strengthened from December 10 th 

### to January 7 th 

### . After the passage of a weak cold front on December 9, 2000, which brought a few hundredths of an inch of precipitation to the region, moisture became available for atmospheric chemistry reactions. Humidity measurements of 90 – 100 % in the morning across the Valley Floor showed a moist atmosphere, with light fog and haze being reported on the exceedance days. These cool damp mornings and strong stability favored the formation of nitrates and sulfates. Synoptically, the eastern Pacific high built over the San Joaquin Valley on December 10, 2000 and dominated the region’s weather through January 7, 2001. The high strengthened and intensified a few days prior to January 1 st 

### , further tightening the lid and trapping pollutants within the San Joaquin Valley boundary layer.

With a strong lid in place aloft and maximum high temperatures in the upper 50’s to low 60’s, the afternoon hours were marked by limited mixing, resulting in increasing particulate potential. Mixing heights at Fresno remained below 500 feet under a strong inversion for 19 hours on January 1 st 

### , breaking out after 4:00 P.M and reforming shortly after 7:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 1,000 feet), but the bulk of the day had limited mixing. Maximum and minimum temperatures for the exceedance day were slightly above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog was reported at the Valley surface during the early morning hours of January 1 st 

### , resulting in slightly lower solar radiation intensities. Along with lower solar

### 75 radiation intensities due to the early morning fog, low sun angle, and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Light fog would be indicative of moderate water content’s that favor the formation of ammonium nitrate. Heavier fogs result in the removal or particulates by wet deposition. Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions around Clovis-Villa, Fresno-1 st 

### , Fresno-Drummond, Bakersfield-California, Bakersfield-Golden, and Oildale-Manor accumulated resulting in the exceedance of the 24-hour PM 10 

### standard on January 1, 2001.

Meteorological conditions remained extremely stable between January 1 st 

### through the

4 th 

### , leading to elevated particulate conditions continuing across the San Joaquin Valley. Without a significant weather disturbance moving through the area to scour out the particulates, PM 10 

### concentrations continued to climb and exceeded the NAAQS at both the FRM and CRPAQS PM 10 

### monitoring sites on the second measured exceedance day on January 4 th 

### . With a strong lid in place aloft and maximum high temperatures in the low 60’s, the afternoon hours on January 4 th 

### , were marked by limited mixing, resulting in increasing particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion for 20 hours on January 4 th 

### . During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing. Maximum temperatures for this exceedance day were above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog reported at the Valley surface during the early morning hours, resulted in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the low sun angle and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion ofpollutants. Both primary and secondary pollutants from local emissions around FresnoDrummond, Bakersfield-Golden, Oildale-Manor, and Bakersfield-California accumulated resulting in the exceedance of the 24-hour PM 10 

### standard on January 4, 2001. The January 4 th 

### exceedances recorded the highest PM 10 

### levels during the January 2001 episode.

Between January 4 th 

### and January 7 th 

### , meteorological conditions began to slowly improve leading to slightly lower but continued elevated particulate conditions across the San Joaquin Valley. Without a significant weather disturbance moving through the area to scour out the particulates, PM 10 

### concentrations continued to remain high and
exceeded the Federal Standard at five FRM PM 10 

### monitoring sites on the third measured exceedance day on January 7 th 

### . The FRM PM 10 

### concentrations at Bakersfield-California (159 μ g/m 3 

### ), Bakersfield-Golden (174 μ g/m 3 

### ), Corcoran-Patterson (165 μ g/m 3 

### ), Hanford-Irwin (185 μ g/m 3 

### ), and Modesto-14 th 

### (158 μ g/m 3 

### ) were captured on January 7 th 

### ( Figure 37, 38, and 39 ). Humidity measurements of 85 – 100 % on the morning of January 7 th 

### , across the Valley Floor showed a relatively moist atmosphere, with light fog and haze being reported. The cool damp mornings and strong stability

### 76 favored the formation of nitrates and sulfates. Synoptically, the eastern Pacific high began to slowly weaken and move into the Intermountain Region on January 7, 2001, slightly weakening the lid over the San Joaquin Valley.

On January 7 th 

### a moderately strong lid was in place aloft and maximum high temperatures were in the mid 60’s. The afternoon hours were marked by limited mixing, resulting in elevated particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion for 16 hours on January 7 th 

### . During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing. Maximum temperatures for this exceedance day were above normal, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog reported at the Valley surface during the early morning hours, resulted in slightly lower solar radiation intensities. Along with lower solar radiation intensities due to the low sun angle and reduced daylight hours, the atmospheric chemistry reactions may have favored the secondary particulate forming regime. Chemical composition and meteorological data showed limited mixing depths and light and disorganized wind flow resulting in minimal transport and dispersion of pollutants. Both primary and secondary pollutants from local emissions around Bakersfield-California and Golden, Corcoran-Patterson, Hanford-Irwin, and
Modesto-14 th 

### , accumulated resulting in the exceedance of the 24-hour PM 10 

### standard on January 7, 2001.

Conclusion

The 2001 episode was marked by a prolonged period of very strong stability and limited mixing, resulting in widespread exceedances of the Federal PM 10 

### Standard across the San Joaquin Valley. Although dispersion was poor, given the length of the episode and the large contributions from secondary components, there was an underlying regional component to this episode as it progressed through January 7 th 

### . Local carbon and geologic contributions added to this regional component and influenced site to site concentration variations. As the episode continued, PM and precursors became more homogeneous across the region. This resulted in PM 2.5 

### concentrations at rural sites lagging those of urban sites, and rural concentrations continued to increase throughout the episode. Historically, the strength of the stability and length of the episode has not occurred often. The January 2001 exceedances were unique in that the meteorology was so strong and lasted for so long, that PM remained trapped and accumulated in the San Joaquin Valley, leading to widespread exceedances of the Federal PM 10 

### Standard by the end of the episode.

### 77 

## 14.0 NOVEMBER 9, 2001 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION

October 31, 2001- November 10, 2001

The period from October 31 through November 10, 2001 was marked by 11 days of strong stability and poor atmospheric dispersion conditions. Strong high pressure both at the surface and aloft over the Intermountain Region dominated the period, leading to light and disorganized wind flow and limited dispersion. The period began with the passage of a vigorous cold front and upper level trough on the 31 st



### , Figure 40.
Between the 31 st 

### and the 10 th 

### , strong stability, light and disorganized wind flow, and poor dispersion conditions resulted in a PM 10 

### exceedance at Hanford on November 9 th



### .

Figure 40: T850 Stability and Precipitation vrs. PM10

at Hanford

Fall and Winter 2001

0 20 40 60 80 100 120 140 16010/1/200110/8/200110/15/200110/22/200110/29/200111/5/200111/12/200111/19/200111/26/200112/3/200112/10/200112/17/200112/24/200112/31/2001PM10(micrograms/meter^3) andPrecipitation (inches)/100

-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14T850 Stability Parameter(C) PPT

PM10 T850 Stability



### At Hanford, a 24-hour PM 10 

### (Particulate Matter) concentration of 155 μ g/m 3 

### was measured. Table 22 outlines federal reference method (FRM) Daily Average Particulate Matter measurements for sites across the San Joaquin Valley (SJV). In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, and aircraft soundings leading to the episode were analyzed.

### 78 TABLE 22: Federal Reference Method (FRM) Daily Average Particulate Matter measurements for sites across the SJV for November 9, 2001.

FRM FRM FRM Site Name 24-Avg. Site Name 24-Avg. Site Name 24-Avg.

10 2.5 10 2.5 10 2.5

Bakersfield-Gold 102 Modesto 115 69 Corcoran* 117 46

Bakersfield-CA 38 Merced-M St. 69 34 Stockton** 97 55

Visalia 74 38 Clovis 68 32 Fresno-1st 70 46

Hanford 155 Fresno-Drum 97 Turlock 124

* -Patterson **- Hazleton

units in μ g/m 3



### The meteorological synoptic analysis showed a period of moderately strong atmospheric stability from October 31 st 

### through the November 10 th 

### . Ahead of a developing trough over the eastern Pacific, a strong mid and upper level ridge developed over the region on the 9 th 

### . This ridge strengthened the inversion over the San Joaquin Valley trapping particulates within the Valley boundary layer. The morning
surface charts of the 9 th 

### depicted a strong surface high over the Intermountain Region, with a surface ridge extending southwestward across central California. The 12Z (4 a.m.) surface pressure gradient was –4.1 millibars from San Francisco (SFO) to Las Vegas (LAS), with isobars (constant surface pressure) orientated southeast to northwest. The alignment of the isobars and the –4.1 (SFO-LAS) millibars pressure gradient, represents light southeasterly wind flow across the San Joaquin Valley. Visibilities throughout the day across the San Joaquin Valley were reporting haze.

The morning temperature aircraft sounding over Fresno on the 9 th 

### showed a strong inversion (stable layer) of 16 degrees Fahrenheit from the surface up to 1,000 feet, turning isothermal (constant temperature) up through 2,500 feet as is evident in Figure
41. The morning temperature sounding over Bakersfield showed a very strong inversion of 22 degrees Fahrenheit from the surface up to 1,500 feet. The temperature sounding on the 9 th 

### , is conducive of elevated PM levels due to low mixing depths and very strong surface based inversions, which keep pollutants trapped near the surface. During the early morning surface observations across the San Joaquin Valley were cold. The minimum temperature recorded at Fresno was 49 degrees Fahrenheit. The minimum temperatures recorded at Bakersfield and Hanford were 45 degrees Fahrenheit. The maximum high temperatures recorded at Fresno and Hanford were 80 degrees Fahrenheit. The maximum high temperature recorded in Bakersfield was 83 degrees Fahrenheit. Fresno hourly temperature data shows very limited mixing conditions below 1,000 feet for over 18 hours of the day, increasing with afternoon

### 79 heating to a maximum mixing depth of 2,000 feet on the 9 th



### .

Figure 41: Atmospheric Temperature Profile at Fresno on November 9, 2001

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

50 55 60 65 70 75

Temperature (deg F)Feet (AGL)



### Upper level charts indicated a strong high over the Intermountain Region, with a ridge extending westward across central California. An upper level trough 750 NM west of San Francisco developed and moved closer to the Californian coastline on the 9 th



### . Weak pressure gradients over the region remained rather flat through the day, leading to light southeasterly wind flow across the San Joaquin Valley.

Table 23 shows the 24 hour daily average wind speeds at SJVAPCD monitoring, ASOS, and CIMIS sites for November 09, 2001.

SJVAPCD Monitoring Sites ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

Clovis 2.4 Fresno 1.5 Shafter/USDA 3.0 Famoso 2.3

Fresno SSP 2.2 Bakersfield 5.3 Firebaugh/Telles 2.3 Westlands 4.1

Corcoran 2.3 Hanford 1.2 Stratford 1.8 Panoche 2.4

Edison 3.6 Madera 3.9 Kettleman 2.8 Arvin-Edison 3.0

Parlier 2.9 Merced 3.6 Visalia/Americas 2.1 Lindcove 2.1

Arvin 2.5 Parlier 1.2 Kesterson 2.4

Visalia 1.4 Blackwells Corner 3.5 Lodi West 1.3

Los Banos 2.5 Modesto 3.4

Manteca 2.8 Fresno State 2.3



### Due to the strong stability lasting for over 10 days, PM 10 

### steadily increase region-wide until the sampling day on November 9 th 

### . With the mid and upper level stability aloft, surface based inversion, and light southeasterly wind flow, this weather pattern was
conducive of elevated PM 10 

### measurements. As is evident in the PM data, local emissions contributed to the exceedance of the National Ambient Air Quality Standards (NAAQS) at Hanford on the 9 th 

### . The preceding day (the 8 th 

### ) had higher atmospheric stability compared to the 9 th 

### , thus PM measurements would have been higher Valley

### 80 wide. Due to decreasing stability and increasing dispersion conditions into the 10 th 

### , PM gradually lowered with the approach of the trough from the eastern Pacific. Widespread showers developed across the region on the 10 th 

### , bringing an end to the November 9 th



### PM event.

### 81 

## 15.0 INTEGRATED ANALYSIS OF ATMOSPHERIC CHEMISTRY AND METEOROLOGY DURING THE NOVEMBER 9, 2001 EPISODE

The November 9, 2001 particulate episode was characterized by a medium length period (a week and a half) of strong stability and light wind flow, which resulted in poor atmospheric dispersion conditions across the San Joaquin Valley. Coarse and fine particulates accumulated during the period, leading to an exceedance of the 24-hour standard at one air monitoring site on November 9, 2001. Concentrations were dominated by the coarse particulates (PM 10 

### ) and were most prevalent across Kern County early in the episode then progressively spread northward to Stanislaus and San Joaquin Counties toward the end of the episode. The highest PM 10 

### measured was 155

μ g/m 3 

### ( Figure 42 ) at Hanford-S Irwin. PM 10 

### at other Valley locations were lower

between 115 to 125 μ g/m 3 

### ( Figure 43 ). During the period, strong high pressure at the surface and aloft resulted in limited afternoon mixing and light offshore wind flow. Cool damp mornings and strong stability contributed to the formation of nitrates and sulfates during the episode. These meteorological conditions led to elevated particulate concentrations. Chemical composition and meteorological data around November 9, 2001, was evaluated and analyzed to identify the characteristics and uniqueness of the
exceedance at Hanford-S Irwin.

Figure 42: Hanford (PM10)

and Fresno 1st (PM2.5) November 9, 2001 Episode

0 20 40 60 80 100 120 140 160

10/28/2001 10/29/2001 10/30/2001 10/31/2001 11/1/2001 11/2/2001 11/3/2001 11/4/2001 11/5/2001 11/6/2001 11/7/2001 11/8/2001 11/9/2001 11/10/2001 11/11/2001Particulate Matter (micrograms/cubic meter) HNF PM10

FAT-1st PM2.5



### Although PM 10 

### sampling is not conducted daily, information from more frequent PM 2.5 

### sampling combined with an assessment of changes in the meteorological conditions suggest that the highest PM 10 

### concentration was not captured on the sampled day. Daily PM 2.5 

### sampling and meteorological conditions suggested that the highest PM 10 

### concentrations may have occurred on November 8 th 

### , when Fresno 1 st 

### measured a peak

PM 2.5 

### concentration of 67 μ g/m 3 

### . No chemical composition data was available for the exceedance day. However, the size fraction data across the Valley indicated that most
of the PM 10 

### was in the coarse fraction, with an average PM 2.5 

### /PM 10 

### ratio of slightly greater than 0.40 at nearby Corcoran ( Figure 43 ).

### 82 Figure 43: Corcoran (PM2.5 & Coarse) and Fresno 1st (PM2.5) November 09, 2001 Episode

0 20 40 60 80 100 120 140 160

1 0 /2 8 /2 0 01 1

0 /2 9 /2 0 01 1

0 /3 0 /2 0 01 1

0 /3

1 /2 0 01 1

1 /1 /2 0 0 1 1

1 /2 /2 0 0 1 1

1 /3 /2 0 0 1 1

1 /4 /2 0 0 1 1

1 /5 /2 0 0 1 1

1 /6 /2 0 0 1 1

1 /7 /2 0 0 1 1

1 /8 /2 0 0 1 1

1 /9 /2 0 0 1 1

1 /1 0 /2 0 01 1

1 /1

1 /2 0 01Particulate Matter (micrograms / cubic meter) COR Coarse

COR PM2.5

FAT-1st PM2.5



### The concentration of coarse material may have been highest at the exceedance site as indicated by the higher coarse fraction at nearby Corcoran compared to other sites in the Valley. In November, many agricultural land preparing and harvesting activities were occurring, potentially contributing to the elevated concentrations of geological material found in the sample. Agricultural burning probably did not contribute to PM on the exceedance day, because November 8 and 9, 2001 were declared No Burn Day’s District-wide. However, burn variances and noncompliant agricultural burns may have contributed to a small portion of the samples. Overnight minimum temperatures in the mid to upper 40’s suggest that residential wood burning may have been a source of
PM 10 

### . The PM 2.5 

### temporal patterns across the Valley showed highest concentrations in Bakersfield on November 3 and 4 followed by peak concentrations on November 5 at Fresno, then the following day on November 6 at Corcoran. A few days later on November 9, the exceedance day at Hanford, peak PM 2.5 

### concentrations were recorded in the northern portions of the Valley (Modesto and Stockton). As discussed below,
both PM 10 

### and PM 2.5 

### concentrations showed that meteorological conditions led to the temporal variability and pollution buildup.

Meteorologically, dispersion worsened and particulate formation conditions strengthened from November 2 nd 

### to the 7 th 

### . However, on November 8 th 

### the day before the exceedance day at Hanford, dispersion conditions began to slightly improve under weaker stability. After the passage of a cold front on October 30 th 

### , which brought 0.16 inches of rainfall to Hanford, moisture was available for atmospheric chemistry reactions. Humidity measurements of 80 – 95% in the morning across the Valley Floor showed a moist atmosphere, with light fog and haze being reported. The cool damp mornings and strong stability favored some formation of nitrate and sulfate particulates. The eastern Pacific high built over the San Joaquin Valley on November 2 nd 

### , and dominated the region’s weather through the 10 th 

### . The high began to slowly break down
on the 8 th 

### , but remained strong through the exceedance day (November 9 th 

### ), trapping pollutants within the San Joaquin Valley boundary layer.

### 83 With a strong lid in place and maximum high temperatures in the upper 70’s to low 80’s on November 9, the afternoon hours were marked by limited mixing, resulting in elevated particulate conditions. Mixing heights at Fresno remained below 500 feet under a strong inversion for 16 hours on November 9, 2001 breaking out by 10:00 A.M. and reforming by 5:00 P.M. During the afternoon hours, there were higher mixing depths (maximum mixing depth of 2,000 feet), but the bulk of the day had limited mixing. Maximum temperatures were above normal for the November 2001 episode, further illustrating the intensity of the high pressure system that was controlling the region’s weather. Light fog being reported at the Valley surface on November 9 th



### , resulted in slightly lower levels of solar radiation intensity. Along with lower solar radiation intensities due to the low sun angle and decreasing daylight hours, atmospheric chemistry reactions may have favored the secondary particulate forming regime.

Chemical composition and meteorological data showed that limited mixing depths and light and disorganized wind flow resulted in minimal transport and dispersion of pollutants. Due to the seasonality of the November 9 th 

### exceedance, the PM 10 

### concentration at Hanford had a dominant coarse fraction compared to exceedances, which occur later in the winter. The duration, moisture availability, light winds, and maximum and minimum temperatures influenced the atmospheric chemistry reactions, during the episode. This led to higher coarse fractions and geological components compared to episodes later in the year. With stagnant weather conditions, local geological sources around Hanford led to the exceedance. Both primary and secondary pollutants from local emissions around Hanford-S Irwin accumulated, resulting in the
exceedance of the 24-hour PM 10 

### standard on November 9, 2001.

### 84 

## 16.0 MAY 19 AND 20, 2002 EPISODE SYNOPTIC METEOROLOGICAL
DISCUSSION

May 19, 2002

A wind blown dust event occurred across parts of the central and southern San Joaquin Valley on May 19, 2002. At McFarland, a 24-hour PM 10 

### (Particulate Matter)

concentration of 407 μ g/m 3 

### was measured. The McFarland measurement was taken 8AM to 8AM daily, whereas all other sites are measured midnight to midnight daily.
Table 24 outlines the Peak and Daily Average Particulate Matter Measurements at McFarland, Corcoran, Clovis, and Fresno-1 st 

### . In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, aircraft soundings, pibal (balloon) wind measurement, and lower air profiler measurements leading to the episode were analyzed.

TABLE 24: Peak and Daily Average Particulate Matter Measurements for sites across the SJV for May 19, 2002

PM 10 

### -Teom PM 10 

### -BAM PM 2.5 

### -BAM Site Name Peak 24-Avg. Peak 24-Avg. Peak 24-Avg.
McFarland * 407 # 

### * * * *

Corcoran 235 39 674 84 27 13
Clovis 106 29 * * * *

Fresno-1 st 

### * * * * 8 4
*-N/A

units in μ g/m 3



### The meteorological synoptic analysis showed that an unseasonably, deep trough developed across the eastern Pacific, the morning of the 19 th 

### . The trough slowly pushed southeastward across California during the afternoon hours. The morning surface charts depicted a surface high pressure ridge draped across central California to Reno, with a thermal low near Las Vegas. The 12Z surface pressure gradient was +9.4 millibars from San Francisco (SFO) to Las Vegas (LAS). A +9.4 millibars pressure gradient means onshore or down-valley flow, which results in strong northwesterly winds across the San Joaquin Valley. A developing cold front curved southward into
the eastern Pacific from a moderate low 600 NM west of Eureka.

The morning temperature soundings over Fresno showed an isothermal (slightly stable) layer up to 4,000 feet. At Bakersfield the temperature sounding showed a similar isothermal layer up to 3,000 feet. The morning pibal wind measurement from Fresno, depicted strong northwesterly flow decoupled from the surface at 37 knots at 1,000 feet continuing northwesterly up to 4,000 feet, then shifting westerly up to 5,000 feet, and then backing southerly above 5,000 feet.

### 85 Upper level charts indicated a strong low 750 NM west of Eureka, with a trough digging southward across the eastern Pacific. A strong temperature gradient (packing) at 850 MB and an intense upper level (300 MB) jet were evident across northwestern California on the 12Z analysis maps. The strong temperature gradient aloft, along with an intense upper level jet, manifested the surface pressure gradient, resulting in strong to gusty winds measured at several hourly-surface meteorological monitoring sites and aloft at the Visalia and Lost Hills lower air profiler sites. Table 25 shows the 24 hour daily average wind speeds at SJVAPCD air monitoring, ASOS, and CIMIS sites for May 19,
2002.

Table 25: 24 hour average wind speeds at SJVAPCD air monitoring, ASOS, and CIMIS sites for May 19, 2002.

SJVAPCD Air Monitor ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

BFLD-Gold 6.8 BFLD Meadows 11.6 FivePoints 11.2 Famoso 5.2 Clovis 7.5 Fresno YI 9.4 Shafter/USDA 6.3 Orange Cove 5.5 Fresno SSP 4.4 Hanford 9 Firebaugh/Telles 5.9 Madera 7.2 Madera Pump 7.5 Madera-AP 10.2 Stratford 7.5 Belridge 6.8
Maricopa 9.2 Merced-AP 8.7 Kettleman 5.2 Merced 4.4

Merced-Coffee 6.2 Modesto-AP 6.7 Visalia/Americas 5.1 Patterson 6.8

Parlier 8.4 Stockton-AP 6.6 Parlier 6.6 Lodi West 2.2 Tracy 9.0 Blackwells Corner 14 Tracy 7.3

Turlock 4.8 Los Banos 8.6 Porterville 4.9

Visalia LAP 6.8 Manteca 4.6 Lost Hills 9.1

Modesto 6.4 Delano 6.1

Fresno State 6.7 Westlands 8.1

Lindcove 3.9 Panoche 6.8

Kesterson 6.1 Arvin-Edison 6.1



### Lower air profiler data from Visalia and Lost Hills showed that with solar insulation (heating) the stable isothermal layer present in the morning began to mix out by 11-12 PDT (18Z-19Z), resulting in strong winds aloft mixing to the surface (Figure 44 and 45)

. The ASOS hourly observations showed northwesterly flow across the San Joaquin Valley (down-valley). At Bakersfield, Hanford, and Lemoore, winds were light and variable in the morning. As the strong temperature gradient aloft and upper level jet began to nose into the region, combined with the strong surface gradient and afternoon heating, gusty northwesterly winds developed across the southern San Joaquin Valley during the afternoon; with Hanford ASOS reporting winds at 10.4 mph gusting to 20 mph and Lemoore with winds at 12.7 mph gusting to 23 mph at the 13:55 PDT
observation. Reduced visibilities of 5 miles were later noted at Hanford around 16:53 PDT when winds were at 17.3 mph gusting to 26.5 mph. Gusty winds continued into the early evening hours and began diminishing after 21:00 PDT. TEOM and BAM hourly measurements, at Corcoran immediately showed the diminishing wind speeds, by measurements lowering to 20 μ g/m 3



### .

### 86 Figure 44: Visalia Lower Air Profiler image for May 19-May 20 th 

### , 2002.

Figure 45: Lost Hill Lower Air Profiler Image for May 19-May 20 th 

### , 2002.

### 87 The wind event on May 19 th 

### , 2002 lasted six to eight hours and resulted in one real time monitoring site at McFarland (407 μ g/m 3 

### ) exceeding the Federal 24-hour PM 10 

### standard. Since other real time particulate monitoring sites did not register above the Federal 24-
hour PM 10 

### standard, the McFarland measurement signifies local wind and emission characteristics. The meteorology did suggest that winds were strong enough to reduce visibilities and impact locally other southern San Joaquin Valley communities during the peak of the dust event.

May 20, 2002

Isolated cases of wind blown dust continued across parts of the central and southern San Joaquin Valley on the 20 th 

### . At Bakersfield Golden, a 24-hour PM 10 

### concentration of

189 μ g/m 3 

### was measured, whereas at Bakersfield California, the PM 10 

### concentration

was 65 μ g/m 3



### . Table 26 outlines the Peak and Daily Average Particulate Matter Measurements at McFarland, Corcoran, Clovis, Fresno-1 st 

### , Bakersfield Golden and California. In order to understand the variability of these measurements, an in depth examination of the synoptic pattern and surface winds and observations, aircraft soundings, pibal balloon measurement, and lower air profiler measurements leading to the episode were analyzed.

TABLE 26: Peak and Daily Average Particulate Matter Measurements for sites across the SJV for May 20, 2002.

10-Teom 10-BAM 2.5-BAM FRM-10
Site Name Peak 24- Avg. Peak 24- Avg. Peak 24- Avg. 24- Avg.
McFarland * 45 * * * * *

Corcoran 45 12 45 20 22 11 15
Clovis 21 6 * * * * 8
Fresno-1 st 

### * * * * 10 1 7

Bak-Gold * * * * * * 189

Bak-Cal * * * * * * 65
*-N/A

units in μ g/m 3



### The meteorological synoptic analysis showed the jet stream carving a deep trough across central California on the morning of 20 th 

### . The morning surface charts depicted a strong surface cold front draped southwestward from Tonopah to Big Sur. The 12Z surface pressure gradient was +4 millibars from San Francisco (SFO) to Las Vegas (LAS). A +4.0 millibars pressure gradient means onshore or down-valley flow.

The morning temperature sounding over Fresno showed a weak inversion of 2 degrees Fahrenheit from the surface up to 500 feet turning unstable through 5,000 feet. At Bakersfield the temperature sounding showed an unstable atmosphere. The morning pibal measurement from Fresno depicted moderate to strong south-southwesterly flow from the surface up to 7,000 feet.

### 88 Upper level charts indicated a strong low 250 NM west of Eureka, with a broad trough covering the eastern Pacific and California. A strong temperature gradient at 850 MB and an intense upper level (300 MB) jet were evident across southern California on the 12Z analysis maps. Along with daytime heating, scattered thunderstorms developed across the southern San Joaquin Valley on the 20 th 

### . These thunderstorms coupled with an intense upper level jet, brought gusty winds across isolated parts of the Valley. In Madera, a small tornado touched down. Table 27 shows the 24 hour daily average wind speeds at SJVAPCD air monitoring, ASOS, and CIMIS sites for May 20, 2002.

Table 27: 24 hour average wind speeds at SJVAPCD air monitoring, ASOS, and CIMIS sites for May 20, 2002.

SJVAPCD Air Monitor ASOS CIMIS

WS WS WS WS

MPH MPH MPH MPH

BFLD-Gold 7.3 BFLD Meadows 11.2 FivePoints 10.4 Famoso 6.6 Clovis 5.9 Fresno YI 9.3 Shafter/USDA 8.1 Orange Cove 5.2 Fresno SSP 5.5 Hanford 8.9 Firebaugh/Telles 5.7 Madera 6.0 Madera Pump 6.3 Madera-AP 10.2 Stratford 7.9 Belridge 7.7
Maricopa N/A Merced-AP 7.2 Kettleman 4.5 Merced 3.3

Merced-Coffee N/A Modesto-AP 7.2 Visalia/Americas 4.2 Patterson 8.3

Parlier 8.2 Stockton-AP 6.7 Parlier 6.3 Lodi West 2.9 Tracy 7.9 Blackwells Corner 14.2 Tracy 5.8

Turlock 6.5 Los Banos 5.8 Porterville 4.6

Visalia LAP 7.3 Manteca 4.6 Lost Hills 11.2

Modesto 7.2 Delano N/A

Fresno State 5.9 Westlands 6.1

Lindcove 4.6 Panoche 5.8

Kesterson 7.5 Arvin-Edison 5.3



### Bakersfield Golden had higher wind speeds on the 20 th 

### compared to the 19 th



### . Figure
46 shows on the 19 th 

### wind characteristics at Bakersfield Golden were marked by a short duration event of elevated winds. On the other hand, the 20 th 

### was marked by gusty, strong winds occurring for most of the day. Peak one hour average wind speed measurements at Bakersfield California measured 13.8 mph at 18-19 PDT, with a 11.8 mph wind speed measured at 17-18 PDT and 19-20 PDT. At the Bakersfield ASOS a peak one hour wind speed measurement was 26 mph on the 20 th 

### . The wind event on

the 20 th 

### at Bakersfield Golden resulted in a PM 10 

### measurement of 189 μ g/m 3 

### ; exceeding
the Federal 24-hour PM 10 

### standard. Since Bakersfield California and other real time and Federal Reference Method (FRM) PM monitoring sites did not measure PM above
the Federal 24-hour PM 10 

### standard, the Bakersfield Golden measurement signifies local
wind and emission characteristics.

### 89 Figure 46: Hourly Average Wind Speeds at Bakersfield Golden
on May 19 and 20, 2002

0 1 2 3 4 5 6 7 80123456789101112131415161718192021222301234567891011121314151617181920212223

May 19 | May 20Wind Speed (meters per second) Wind Speeds at Bakersfield Golden(mps)

### 90 

## 17.0 REFERENCES

Hackney, Richard, Larimer Xo, and Ranzieri, Andrew. 1991. Analysis of Upper Air Synoptic Parameters Relating to PM10 Episodes in the San Joaquin Valley. California Air Resources Board, Sacramento, California.

http://www.arb.ca.gov/airways/CRPAQS/DA/PMEpisodes.htm . June 24, 2004. PM Episodes: Central California Air Quality Studies – CCOS & CRPAQS. California Air Resources Board. Sacramento, California.