# Exceptional Event Demonstration Package for the Environmental Protection Agency

Big Piney and Boulder , Wyoming Ozone Standard Exceedance s June 14 , 2012

122 West 25 TH 

### Street , Cheyenne, WY 82002 State of Wyoming Department of Environmental Quality/Air Quality

DivisionP a g e | 1

N OTE S TO READER:

This document contains several electronic enhancements such as time animations and figure enlargements. Viewing this document in its electronic format will aid the reader in reaching a better understanding of the material. In addition, t his document has been prepared to stand alone as a hard copy without th e electronic enhancements.

All time references refer to Mountain Stan dard Time (MST) unless otherwise noted. EPA utilizes Mountain Standard Time (MST) consistently throughout the entire year in respect to ambient and ground based meteorological monitoring data collection and reporting.P a g e | 2

LIST OF ACRONYMS AND TERMS

AG L Above Ground Level AJAX Alpha Jet Atmospheric eXperiment AMSL Above Mean Sea

- level AQI Air Quality Index AQS Air Quality System ° C KM - 1 Degrees Celsius per Kilometer CFR Code of Federal Regulations CO Carbon Monoxide DALR Dry Adiabatic Lapse Rate DU Dobson Unit ECC Electrochemical Concentration C ell EDAS Eta Data Assimilation System EPA Environmental Protection Agency ELR Environmental Lapse Rate GMD Global Monitoring Division GOES Geostationary Operational Environmental Satellite h7

- h5 700

- 500 mb layer HYSPLIT HYbrid Single

- Particle Lagrangian Integrated T rajectory IOP Intensive Operational Period IPV I sentropic P otential V orticity K Kelvin kPA K ilopascal LIDAR Light Detection And Ranging mb Millibar MDT Mountain Daylight Time MSL Mean Sea Level MST Mountain Standard Time NAAQS National Ambient Air Quality Standards NAM North American Mesoscale NARR North America Regional Reanalysis NCDC National Climatic Data Center NOAA National Oceanic and Atmospheric Administration NO N itric O xide NO 2 Nitrogen Dioxide NWS National Weather Service O 3 Ozone ppb Parts Per Billion Pphm/vol Parts Per Hundred Million / Volume PT Potential Temperature PVU Potential Vorticity Unit QA/QC Quality Assurance/Quality Control RAOB Radiosonde observat ions RAP Rapid Refresh model RAQMS Realtime Air Quality Modeling SystemP a g e | 3

RUC Rapid Update Cycle model RH Relative Humidity SI Stratospheric Intrusion SO 2 Sulfur Dioxide START08 Stratosphere

- Troposphere Analyses of Regional Transport 2008 UG Upper Green UGR B Upper Green River Basin UGWOS Upper Green Winter Ozone Study UTC C oordinated U niversal T ime UV Ultraviolet WDEQ/AQD Wyoming Department of Environmental Quality/Air Quality Division VOC Volatile Organic CompoundP a g e | 4

Table of Contents
LIST OF ACRONYMS AND TERMS

................................ ................................ ................................ .................. 2

EXECUTIVE SUMMARY

................................ ................................ ................................ ................................ .. 6

BACKGROUND

................................ ................................ ................................ ................................ ............. 10

Document Format

................................ ................................ ................................ ................................ ... 10

Ground Level Ozone Formation

................................ ................................ ................................ .............. 10
Atmospheric Structure

................................ ................................ ................................ ............................ 10
Composition of Stratospheric Air

................................ ................................ ................................ ............ 10
Stratospheric Intrusions, Tropospheric Folding, and Identifying Stratospheric Air

................................ 11
Background Summary

................................ ................................ ................................ ............................. 13

METHODOLOG Y FOR DIAGNOSING SI’S AND SI EVENTS

................................ ................................ ............ 14

SUMMARY OF DIAGNOSING SI EVENTS

................................ ................................ ................................ ...... 16

JUNE 14, 2012 EXCEPTIONAL EVENT

................................ ................................ ................................ .......... 17
Summary

................................ ................................ ................................ ................................ ................. 17
Public Notification and EPA’s Air Quality System Data

................................ ................................ ........... 17 Data QA/QC and Equipment

................................ ................................ ................................ ................... 19
Statistical Analysis

................................ ................................ ................................ ................................ ... 19
Supporting Meteorological Data: Weather Overview

................................ ................................ ........ 23
Supporting Meteorological Data: GOES Total Column Ozone Data

................................ ................... 24
Supporting Meteorological Data: AIRS Satellite Measurements of Carbon Monoxide

...................... 25
Supporting Meteo rological Data: Isentropic Potential Vorticity, Relative Humidity, and Potential Temperature Vertical Cross

- Sections

................................ ................................ ................................ .. 26
Supporting Meteorological Data: Back Trajectory Analysis

................................ ................................ 30
Supporting Meteorological Data: SI

- Composite Chart

................................ ................................ ....... 35
Supporting Meteorological Data: Vertical mixing as shown by lapse rates

................................ ....... 38
Supporting Meteorological Data: Upper Air RAOB’s

................................ ................................ .......... 40
Supporting Meteorological and Am bient Data: Surface

- based data

................................ .................. 43

SUMMARY AND CONCLUSIONS

................................ ................................ ................................ .................. 48
Bibliography

................................ ................................ ................................ ................................ ................ 51

APPENDIX A

- Doc umented Stratospheric Intrusion Events

................................ ................................ ....... 54
March 12, 1978

................................ ................................ ................................ ................................ ... 54

November 7

- 8, 1999

................................ ................................ ................................ ........................... 55P a g e | 5

April 28, 2008

................................ ................................ ................................ ................................ ...... 55

APPENDIX B

- D iagnosis Example

................................ ................................ ................................ ................ 57
Supporting Meteorological Data: Weather Overview

................................ ................................ ........ 57
Supporting Meteorological Data: GOES Band

- 12 Data

................................ ................................ ....... 58
Supporting Meteorological Data: Upper Air RAOB’s

................................ ................................ .......... 59
Supporting Meteorological Data: Isentropic Pot ential Vorticity, Relative Humidity, and Potential Temperature Cross

- Sections

................................ ................................ ................................ ............... 60

APPENDIX C

- NARR Explained

................................ ................................ ................................ .................... 62

APPENDIX D

- AQS Data

– AMP 350, Raw Data Report for Big Piney, Boulder, South Pass, Daniel, Pinedale, Juel Spring, Yellowstone and Grand Teton Na tional Parks 1

- hour average ozone for June 13

- 16,
2012.

................................ ................................ ................................ ................................ ........................... 65

APPENDIX E

- AQS Data

– AMP 350NW, Raw NAAQS Ozone Average Data Report for Big Piney, Boulder, South Pass, Daniel, Pinedale, Juel Spring, Yellowstone and Grand Teton National Parks for June 13

- 16,
2012.

................................ ................................ ................................ ................................ ........................... 66

APPENDIX F

- AQS Data

– AMP 350, Raw Data Report for Big Piney, Boulder, South Pass, Daniel, Pinedale, Juel Spring, Yellowstone and Grand Teton National Parks all air quality and meteorological parameters
for June 13

- 16, 2012

................................ ................................ ................................ ................................ ... 67

APPENDIX G

- AQS Data

– AMP 350, Raw Data Report for the State of Idaho all air quality and meteorological parameters for June 13

- 16, 2012.

................................ ................................ ..................... 68

APPENDIX H

- 2012 2 nd and 4 th Quarter QA Audit Reports.

................................ ................................ ........ 69P a g e | 6

EXECUTIVE SUMMARY

The Wyoming Department of Environmental Quality/Air Quality Division (WDEQ/AQD) has determined that a stratospheric i ntrusion created elevated ozone readings resulting in an 8

- hour ozone standard exceedance at the Boulder and Big Piney , Wyoming ozone monitor s located in the Upper Green River Basin (UGRB) of western Wyoming o n June 14 , 2012 (refer to Figure 1 for monitor location s )

. During the interval from late winter to late spring in the northern hemisphere, weather producing systems (i.e. tropospheric storm systems, upper level disturbances or upper level storm systems) aid in causing the tropopause to “fold” or descend into the troposphere where our weather occurs. Tropopause folding allows ozone

- rich air from the stratosphere to enter the troposphere, also called a stratospheric intrusion (SI), creating the potential for ground level ozone monitors over the higher terrain o f the western United States to experience elevated readings.
Throughout June 13

- 14, 2012, an upper level atmospheric disturbance with an associated SI moved over central Idaho injecting ozone

- rich air into the troposphere. The ozone

- laden air then moved o ver western Wyoming creating elevated ozone readings resulting in 8

- hour ozone standard exceedances of 76 and 77 ppb at the Boulder and Big Piney, Wyoming ozone monitors

, respectively.
Additionally, the Yellowstone and Grand Teton National Park ozone monit or s as well as t he AQD ozone monitors at South Pass, Daniel, Pinedale, and Juel Spring measured elevated 1

- hour
average ozone values from the upper 60’s to upper 70’s ppb during the SI event (refer to Figure 2 ). (Note to reader: the Pinedale CASTNET site was not operational during June 2012 due to a prolonged power outage).

It has been documented (T. S. ENVIRON 2008) that e levated ozone values can occur at the UGRB ozone monitors o f Boulder, Big Piney, Pinedale, Daniel, and Juel Spring becaus e of light winds

, snow cover , and strong inversions during the January

- March winter ozone season. However, during the June 14, 2012 period of elevated ozone, strong winds buffeted the UGRB prior to the SI event , and no snow cover or strong inversions were present. Accumulation of surface

- based ozone precursors did not occur because meteorological conditions were not supportive of precursor buildup prior to ele vated ozone readings.
Statistical analyses performed on the Boulder and Big Piney data show that the June 14 , 2012 ozone data w as statistically significantly higher than values recorded during June of each year from 200 5

- 2012 (Boulder) and 2011

- 2012 (Big Piney) . The AQD performed a thorough evaluation of the June 14 , 2012 episode, and is confident that the Boulder and Big Piney event presented in this document is the result of a stratospheric intrusion.
Quality Assurance/Quality Control (QA/QC) chec ks of the Boulder and Big Piney ozone monitor s during 2012 confirm that the monitor s w ere running properly. Independent audit results for the second and fourth quarters of 201 2 are consistent with 40 CFR Part 58, Appendix A, Section 3.2 and the Quality As surance Project Plan for the Boulder and Big Piney monitoring project s

. With the preceding points in mind, the WDEQ/AQD submits the June 14 , 2012 Boulder and Big Piney ozone exceedance s as a case for the Environmental Protection Agency’s (EPA)P a g e | 7

concurrence regarding the stratospheric intrusion of ozone as being an exceptional event as outlined by the final “Treatment of Data Influenced by Exceptional Events” Final Rule. T he W DEQ/A QD presents supporting evidence which clearly shows that the exceptional event passed the four required tests A

- D under 40 CFR 50.14 (3)(iii). Specifically:
(A) The event satisfies the criteria set forth in 40 CFR 50.1(j); (B) There is a clear causal relationship between the measurement under consideration and the event that is cla imed to have affected the air quality in the area; (C) The event is associated with a measured concentration in excess of normal historical fluctuations, including background; and (D) There would have been no exceedance or violation but for the event.

Figure 1 . WDEQ/AQD Air Quality Monitor Network Sites. Click to enlarge image.P a g e | 8

Figure 2 . 1

- hour average ozone data for Wyoming ozone monitors for June 13

- 16, 2012

.

Criteria (A) states that “[t]he event satisfies the criteria set forth in 40 CFR 50.1(j)”:
40 CFR 50.1 (j) requires that an exceptional event “affects air quality, is not reasonably controllable or preventable...” and is a “...natural event”. The Exceptional Events R ule Preamble and the 40 CFR 50 Appendices I & P specifically list stratospheric intrusion of ozone as a natural event that could affect ground level ozone concentrations. This packet includes data and graphics that display a weather disturbance

, and clear ly show an intrusion of stratospheric air that affected ambient air quality during June 14 , 2012 at the Boulder and Big Piney ozone

m onitor s

.
Criteria (B) states that “ [ t ] here is a clear causal relationship between the measurement under consideration and the event that is claimed to have affected the air quality in the area ” :

The causal relationship is a basic one in which the ozone standard exceedance s were cau sed by tropospheric folding bringing ozone

- rich air down to the earth’s surface. For the exceedance s that occurred on June 14 , 2012

, an intrusion of stratospheric air occurred over central Idaho upwind of the Boulder and Big Piney monitor s and injected ozone

- rich air into the area above and surrounding the Boulder and Big Piney ozone monitor s

. The causal nature of the SI’s impact on ozone values at the Boulder and Big Piney ozone monitor s is further supported by the corroboration of ground

- based air quality data to the spatial and temporal accuracy of the meteorological analysis. 0 10 20 30 40 50 60 70 80 90 100

6/13/12 12:00 AM 6/14/12 12:00 AM 6/15/12 12:00 AM 6/16/12 12:00 AM Ozone (ppb) 

## June 13

- 16, 2012 Ozone

South Pass

Boulder

Daniel

Pinedale

Big Piney

Juel Spring

Yellowstone

Grand TetonP a g e | 9

Criteria ( C) states that “ [ t]he event is associated with a measured concentration in excess of normal historical fluctuations, including background”:

Statistical analysis of June 14 , 2012 data clearly shows that the exceptional event was statistically significantly higher than data recorded during prior months of June from 2005

- 2012 (Boulder) and 2011

- 2012 (Big Piney)

.

Criteria (D) states that “[t]here would have been no exceedance or violation but for the event”:

Th e SI allowed ozone

- rich air to d escend to the Boulder and Big Piney ozone monitor s creating elevated 1

- hour average ozone values resulting in an 8

- hour ozone exceedance at both ozone monitors. T he exceedances of the ozone National Ambient Air Quality Standards ( NAAQS ) would not have occurred “b ut for” the SI.

T he 75 th percentile hourly ozone concentrations does not exceed 55 ppb for the month of June for the years tested 2005

- 2012 (Boulder) and 2011

- 2012 (Big Piney) for statistical significance

. Hourly concentration s monitored during June 14 , 2012 were outliers for the month s of June 200 5

- 2012 (Boulder) and 2011

- 2012 (Big Piney)

. Statistics demonstrating that ozone levels were unusually elevated affirm that the exceedance s of the ozone National Ambient Air Quality Standards (NAAQS) would not have happened “but for” the SI event having occurred during June 13

- 14 , 2012

. In brief, the WDEQ/AQD concludes that an SI occurred during June 13

- 14 , 2012 resulting in an exceptional ev ent. This exceptional event has passed the four criterion tests under 40 CFR 50.14 (3)(iii). Consequently, the WDEQ/AQD is requesting EPA ’s concurrence that the event was exceptional and for the exclusion from the Air Quality System (AQS) database of the Big Piney and Boulder 1

- hour average oz one data for the following times:

Table 1. Big Piney and Boulder times and dates for AQS data exclusion.

Site Begin Time/Date(s) End Time/Date(s) Big Piney 09 00 MST June 14, 2012 1 90 0 MST June 14, 2012 Boulder 0900 MST June 14, 2012 2100 MST June 14, 2012P a g e | 10

BACKGROUND

Document Format The following discussion provides background information on SI’s as well the methodolog y utilized in identifying SI’s. Subsequently, t he June 14, 2012 event is present ed with evidence support ing the premise that an SI occurred creating a period of elevated 1

- hour average ozone values resulting in ozone standard exceedances at the Boulder and Big Piney ozone monitors. The reader is encouraged to examine A ppendix A, “Documented Stratospheric Intrusion Events” and Appendix B, “Diagnosis Example” to obtain further information on SI’s

.
Ground L evel Ozone Formation

“ Ozone (O 3 ) is a gas composed of three oxygen atoms. It is not usually emitted directly into the air, but at ground le vel is created by a chemical reaction between oxides of nitrogen (NOx) [including nitrogen dioxide (NO 2 )] and volatile organic compounds (VOC s ) in the presence of sunlight. Ozone has the same chemical structure whether it occurs miles above the earth or a t ground level and can be "good" or "bad," depending on its location in the atmosphere. ” (Source: EPA website). Specifically, NO 2 is split up by ultraviolet (UV) sun light to give n itric o xide ( NO ) and an oxygen atom, which combines with molecular oxygen (O 2 ) to give ozone

. Calm winds, or stagnant conditions a ssist the process of allowing the O 3 precursors of NO x (NO 2 ) and VOCs to accumulate in order to produce O 3 . Unlike ozone of stratospheric origin, g round

- based ozone typically forms during the daylight hours under stagnant weather conditions (over several days in some cases) and dissipates a few hours after sunset.
Atmospheric Structure The troposphere is the layer of air adjacent to the earth’s surface and contains our weather (i.e. wind, rain, snow, thunderstorms, etc.) The troposphere also contains variable amounts of water vapor and carbon monoxide (CO), extends to a height of roughl y 11 km (6.8 mi) Above Mean Sea

- level ( AMSL ) , and varies in depth from the earth’s polar regions to the equator. Directly above the troposphere, the stratosphere exists with the tropopause separating the stratosphere from the troposphere. The tropopause is “...usually characterized by a n abrupt change of lapse
rate 1 ” (American Meteorological Society 2010)

. The stratosphere is the “...region of the atmosphere extending from the top of the troposphere [t he tropopause ] , at heig hts of roughly 10

– 17 km ...[and] is characterized by constant or increasing temperatures with increasing height and marked vertical stability ” (American Meteorological Society 2010)

. Composition of Stratospheric A ir “While the major constituents of the stratosphere are molecular nitrogen and oxygen, just as in the troposphere , the stratosphere contains a number of minor chemical species that result from photochemical reactions in the intense ultraviolet radiation envi ronment. Chief among these is

oz one...” (American Meteorological Society 2010)

. While the troposphere co ntains variable amounts of O 3 , CO , and water vapor, the stratosphere lacks CO and water vapor (Pan, Randel, et

1 Lapse rate is defined as the change of temperature with the increase of height in the atmosphere.P a g e | 11

al. 2004 ; Newell, et al. 1999; Stoller, et al. 1999 ) . Figure 3 demonstrates the typical concentration of ozone with height extending from the earth’s surface through the stratosphere.

Figure 3 . Vertical profile of ozone. (Graphic adapted from NASA).

Stratospheric Intrusions, Tropospheric Folding, and Identifying Stratospheric Air Weather producing systems (i.e. tropospheric storm systems, upper level disturbances or upper level storm systems) contain atmospheric spin or vorticity, which induces vertical motion: either upward or downward motion. From late winter to late spring in the northern hemisphere, vertical motion associated with upper level disturbances aids in causing the tropopause to “fold” or descend into the troposphere where our weather occurs (Danielsen 1968)

. Because of tropopause folding, an intrusion of stratospheric air containing high concentrations of ozone penetrates into the troposphere (Reed 1955) releasing ozone

- rich air from the stratosphere to the troposphere. As a result, the SI creates the potential for ground level ozone monitors over the higher terrain of the western United States to experience elevated ozone readings.

SI’s are a tangible phenomenon. One study ( Click to view press release regarding study ) analyzed over 105,000 aircraft soundings, and discovered that just over 50% of the soundings contained regions of high oz one and low water vapo r content occurring below the tropopause (Newell, et al. 1999) . The presence of areas of high ozone concentrations and low water vapor located below the tropopause are components of an SI signature.

While the concentrations of O 3 , CO , and relative humidity (RH) aid one in identifying air of stratospheric origin, additional stratospheric tracers 2 should be employed and include: isentropic potential vorticity (IPV) and potential temperature (PT). IPV is a proxy for atmospheric spin and is a conservative property 3 with values of up to two orders of magnitude [100 times] greater for stratospheric air than that of tropospheric air (Shapiro 1980) . Therefore, IPV can serve as a

2 “A chemical or thermodynamic property of the flow that is conserved during” air motion (American Meteorological Society 2010)

. 3 “ A property with values that do not change in the course of a particular series of events ” (American Meteorological Society 2010) . Namely, a property whose values do not change over the course of travel.P a g e | 12

tracer of stratos pheric air. One unit of IPV (1

- PVU) 4 typically represents the tropopause (Shapiro 1980) , and as one ascends beyond the tropopause into the stratosphere, the value of IPV increases correspondingly. However, within the last decade a s tudy by Pan revealed that using only IPV to define the tropopause is problematic. In fact, the thermal tropopause height “...spans a broad range of...” IPV values and varies latitudinally and seasonally (Pan 2004). Therefore, based on the AQD’s review o f the background material regarding IPV usage, the AQD recognizes that one cannot use IPV alone in identifying air of stratospheric origin.

Potential temperature is “t he temperature that an unsaturated parcel of dry air would have if brought adiabatically 5 and reversibly from its initial state to a standard pressure, p0, typically 100 kPa ” (or 1000 mb) (American Meteorological Society 2010) . Stratospheric air has much higher values of potential temperature than that of troposp heric air. As stratospheric air penetrates the troposphere, its potential temperature is higher than that of tropospheric air surrounding the SI. One can visualize this effect by cross

- section examination of IPV and PT. The slope of isolines 6 of potential temperature increase markedly showing this effect (Reed 1955) . Figure 4 shows a generic vertical cross

- section of IPV and PT. Note the area of sloping isolines of PT and the 1

- PVU surface juxtaposed on one another. The slope of the isoline s of PT increases significantly highlighting the signature of stratospheric air descending into the troposphere.

Figure 4 . Vertical cross

- section of potential temperature (thin solid lines) and IPV (thick solid lines). Potential temperature units are degrees Kelvin (K). IPV units in potential vorticity units. Click image to enlarge.

4 IPV and PVU are utilized throughout this document and are synonymous. For further information, please consult: http://www.comet.ucar.edu/class/aes_canada/04

- 1/html/docs/PVintro.pdf
5 “Adiabatic process

— A process in which a system does not interact with its surroundings by virtue of a temperature difference between them. In an adiabatic process, any change in internal energy (for a system of fixed mass) is solely a consequence of worki ng. For an ideal gas and for most atmospheric systems, compression results in warming, expansion results in cooling” (American Meteorological Society 2010) . Compression and expansion arise from downward atmospheric vertical m otion and atmospheric upward vertical motion respectively.
6 “... a line of equal or constant value of a given quantity, with respect to either space or time ...” (American Meteorological Society 2010)P a g e | 13

Background Summary The stratosphere contains high concentrations of ozone compared to the troposphere . At times, from late winter until late sp ring in the northern hemisphere, tropospheric storm systems act synergistically with tropopause folds to inject stratospheric ozone into the troposphere via an SI. Compared to tropospheric air, stratospheric air is typically much drier, has higher values of IPV and PT, and contains lower quantities of CO.
Data from research aircraft have determined that tropopause folds (SI’s) contain ample O 3 , dry air, and low concentrations of CO. Mathematical calculations based on the aircraft data also verify that the SI’s had greater than 1

- PVU and had higher PT values compared to those of the troposphere surrounding the SI. 7

7 The reader is encouraged to e xamine Appendix A, “Documented Stratospheric Intrusion Events” and Appendix B, “Diagnosis Example” to obtain further information on SI’s.P a g e | 14

METHODOLOGY FOR DIAGNOSING SI’S AND SI EVENTS Since the majority of SI’s occur from the late winter to late spring (Da nielsen 1968) , elevated ozone episodes occurring during this time merit further analysis. The AQD recognizes that a combination of indicators should be employed when diagnosing an SI. One should not rely on any single indicator alone. The following offers a methodology to diagnose whether an SI has occurred:
Summary of the synoptic scale meteorology
An examination of the 500 mb heights and vorticity chart may indicate an SI if an upper level atmospheric disturbance occurred at some point before gro und level ozone values increased. By inspecting the 500 mb pressure chart by way of the North America Regional Reanalysis (NARR) 8 , one can establish whether an upper atmospheric disturbance took place.
Employ Geostationary Operational Environmental Satellite (GOES) data

“ GOES satellites provide the kind of continuous monitoring necessary for intensive data analysis. They circle the Earth in a geosynchronous orbit, which means they orbit the equatorial plane of the Earth at a speed matching the Earth 's rotation. This allows them to hover continuously over one position above the Earth’s surface. The geosynchronous plane is about 35,800 km (22,300 miles) above the Earth, high enough to allow the satellites a full

- disc view of the Earth ....t he main mis sion [of GOES satellites] is carried out b y the primary instruments, the i mager and the s ounder. The imager is a multichannel instrument that senses radiant energy and reflected solar energy from the Earth's surface and atmosphere. The Sounder provides d ata to determine the vertical temperature and moisture profile of the atmosphere, surface and cloud top temperatures, and ozone distribution. ” (Source: NOAA Satellite and Information Service, National Environmental Satellite, Data, and Information Service , Office of Satellite Operations website ).
Recent studies and research have shown that usage of GOES data is a useful tool in diagnosing SI’s (Jin, et al. 2008) . O ne can use the GO ES total column ozone 9 data in

8 “The North America Regional Reanalysis (NARR) Project is a reanalysis of historical observations using a 32

- km version of the National Centers for Environmental Prediction (NCEP) 1993 operational ETA model and ETA data assimilation system (EDAS). ...The domain of analyses includes North and Central America

... The pe riod of the reanalyses is from October 1978 to the p resent and analyses were made 8 times daily (3 hour intervals). Horizontal boundary conditions are derived from the NCEP/DOE Global Reanalysis.” For further information, please refer to visit this website: http://www.esrl.noaa.gov/psd/data/gridded/data.narr.html
9 Total column ozone (TCO) is estimated every hour using GOES Sounder data. The ozone retrieval is generated by application of a regression technique as described in Li et a l 2007. Estimates are currently limited to cloud

- free regions of the GOES

- E (12) &

- W (11) Sounder sectors. Each image is a Derived Product Image (DPI), wherein an 8

- bit brightness value representing TCO is assigned within the retrieval program for each cloud

- free Field

- of

- View (FOV). Band

- 8 (11.0um) is used for the DPI image background. Total column ozone is measured in Dobson Units (100 DU = 1 mm of thickness at Standard Temperature and Pressure (STP)). Features such as upper level low

pressure syste ms and frontal boundaries can often be identified in the TCO imagery. (Source: Data Center at the Space Science and Engineering Center (SSEC) of the University of Wisconsin

– Madison)P a g e | 15

Dobson Units (DU) 10 to locate areas of increased column ozone (Wimmers, et al. 2003; Knox and Schmidt 2005)

. Numerous studies have shown a positive correlation between an SI and an increase in the total column ozone. As the SI injects ozone into the troposphere, total column ozone increases (Reed 1950 ; Schubert and Munteanu 1988 ; Mote, Holton and Wallace 1991)

.
The GOES Band

- 12 channel is a water vapor channel that portrays the moisture content of the layer approximating 300

- 400 mb (Wimmers, et al. 2003)

. Use of the water vapor image helps highlight an area of substantially drier air originating from aloft mixing down to lower levels of the troposphere. Since SI’s contain dry air and transverse through the 300

- 400 mb tropospheric layer, one can use the 6.5

- micrometer GOES Band

- 12 water

va por channel to diagnose the presence of an SI signature.
Employ Radiosonde observations

Another way to diagnose the existence of stratospheric air is by examining Radiosonde observations ( RAOB ’ s )

. RAOB’s are comprised of three elements: a radiosonde (an instrument th at measures and transmits pressure, relative humidity, and temperature data to a ground receiver), a parachute, and a balloon. The balloon is released into the sky carrying the r adiosonde and parachute. A layer of dry air is a key signature of stratosphe ric air (as measured by a radiosonde) and is depicted by an increase in temperature and a decrease in dew po int (moisture) with height (Newell, et al. 1999 ; Stoller, et al. 1999 )

. When coupled with a radiosonde, an ozonesonde provides direct evidence of the vertical profile of ozone concentration. An ozonesonde contains an electrochemical concentration cell (ECC) that senses ozone as is reacts with a dilute solution of potassium io dide to produce a weak electrical current proportional to the ozone concentration (partial pressure) of the sampled air

. Employ 4

- D “0

- hour” Rapid Refresh (RAP) data (IPV, RH, and PT)

The RAP is a numerical weather analysis tool utilized by meteorologis ts to predict weather conditions. The R AP is initialized with real

- time data, and the 0

- hour analysis for any given hour is a very close approximation to initial actual conditio ns (Benjamin, et al. 2004). RAP “analysis” data can be used to illustrate the signature of an SI (refer to Figure 4) by portrayin g IPV, RH, and PT (Murray 2003) via a vertical cross

- section or a time

- height cross

- section of the atmosphere.

10 The Dobson Unit is the most common unit for measuring ozone concentr ation. One Dobson Unit is the number of molecules of ozone that would be required to create a layer of pure ozone 0.01 millimeters thick at a temperature of 0 degrees Celsius and a pressure of 1 atmosphere (the air pressure at the surface of the Earth). Expressed another way, a column of air with an ozone concentration of 1 Dobson Unit would contain about 2.69x1016 ozone molecules for every square centimeter of area at the base of the column. Over the Earth’s surface, the ozone layer’s average thickness is about 300 Dobson Units or a layer that is 3 millimeters thick.P a g e | 16

Perform trajectory analysis
A means of tracking the path of air parcels is by employing b ack ward and forward trajectories to demonstrate the origins of “pockets” of high ozone due to SI’s. One can use the HYSPLIT software package (Draxler and Rolph n.d.) to demonstrate not only the origin of air parcels but also evo lution of air parcels as they move through the troposphere. By selecting a range of altitude s and time s at a specific location , one can use HYSPLIT to analyze the path air parcels took prior to arriving at a selected point (backward trajectories). Conver sely, one can employ the same analysis technique to determine the eventual fate of air parcels originating from a specific point (forward trajectories). In the case of SI’s, trajectory analysis is used to show how “pockets” of air containing high ozone concentrations arrived at monitors which indicated elevated ozone levels (Sørensen and Nielsen 2001 ; Aulerio, et al. 2005)

.

SUMMARY OF DIAGNOSING SI EVENTS To review, the key features of a SI event are:
An upper level disturbance producing a tropospheric fold and subsequent SI.
Depicted in cross

- sections or time

- height cross

- sections by sloping lines of PT, by 1

- PVU or greater descending into the troposphere, and by an area of dry air.

A well

- mixed or even turbulent atmosphere resulting from an upper leve l disturbance and creating conditions for vertical movement of SI

- air to the earth’s surface

. Additionally, WDEQ/AQD is a member of a national EPA SI workgroup that was formed during 2012. The primary goal of the w orkgroup is to diagnose past SI events, i ncluding the June 13

- 14, 2012 event described in this document.P a g e | 17

JUNE 14 , 2012 EXCEPTIONAL EVENT

Summary During June 13

- 14, 2012, an upper level atmospheric disturbance associated with an SI moved over central Idaho injecting ozone

- rich air into the troposphere. The ozone

- laden air then moved over western Wyoming c reating elevated ozone readings resulting in 8

- hour ozone standard exceedance s of 76 and 77 ppb at the Boulder and Big Piney, Wyom ing ozone monitor s , respectively.
Additionally, the Yellows tone and Grand Teton National Park ozone monitors as well as the AQD ozone monitors at South Pass, Daniel, Pinedale, and Juel Spring measured elevated 1

- hour average ozone values from the upper 60’s to upper 70’s ppb during the SI event (refer to Figure 5) . (Note to reader: the Pinedale CASTNET site was not operational during June 2012 due to a prolonged power outage).

Furthermore, EPA’s June 14, 2012 daily peak ozone air quality index (AQI) map illustrates the effects of the SI over Idaho and western Wy oming (Figure 6) . Central/southern Idaho and western Wyoming were either in the “moderate” category (yellow shade) or “ unhealthy for sensitive groups ” category (orange shade).

It has been documented (T. S. ENVIRON 2008) that elevated ozone values can occur at the UGRB ozone monitors of Boulder, Big Piney, Pinedale, Daniel, and Juel Spring because of light winds, snow cover, and strong inversions during the January

- March winter ozone season. However, during the June 14, 2012 period of elevated ozone, strong winds buffeted the UGRB prior to the SI event, and no snow cover or strong inversions were present. Accumulation of surface

- based ozone precursors did not occur because meteorological conditions were not supportive of precursor buildup prior to elevated ozone readings.

For the month of June from 2000 to 2012, Wyoming ground level, 1

- hour average ozone levels at all ozone monitors ranged from 3 4

- 5 2 ppb ( 25

- 75% interquartile range) with a mean of 4 2

. 6 ppb . However, when an SI occurs, 8

- hour average values [derived from the 1

- hour average] can exceed 80 ppb on a time scale of a few hours to a few days (Mohnen and Reiter 1977)

. While not exceeding 80 ppb, 8

- hour average ozone g reater than 75 ppb occurred for three consecutive hours at Boulder and Big Piney on June 14, 2012. At 4 pm MST on June 14 , 201 2 , the Boulder ozone monitor recorded the highest 1

- hour average ozone value of 80 ppb resulting in a daily maximum rolling 8

- hour average of 76 ppb. Furthermore, the Big Piney ozone monitor recorded the highest 1

- hour average ozone value of 83 ppb at 3 and 4 pm MST, June 14, 2012 resulting in a daily maximum rolling 8

- hour average of 77 ppb.

Publi c Notification and EPA’s A ir Q uality S ystem Data WDEQ/AQD’s Wyoming Visibility Monitoring Network (WyVisNet) website provide d near real

- time pollutant a nd meteorological data from Boulder and Big Piney and was operational during the June 14 , 2012 elevated ozone event. Citizens of Wyoming have continuous access to WyVisNet via the internet, which serves as a means of public information dissemination regarding elevated ozone readings. Additionally, Bould er and Big Piney ozone data are reported to the EPA’s AIRNow website

.P a g e | 18

The public also has access to EPA’s Air Quality System (AQS) database that houses validated data from the AQD’s monit oring stations. Figure 5 shows a time

- series of 1

- hour average ozone valu es from AQS for the period from June 13

- 1 6 , 201 2

.
Figure 5. Time s eries of 1

- hour average ozone (ppb) for Wyoming monitors from June 13

- 1 6 , 2012.

Figure 6. EPA Daily Peak Ozone AQI for June 1 4 , 2012. Click image to enlarge. 0 10 20 30 40 50 60 70 80 90 100

6/13/12 12:00 AM 6/14/12 12:00 AM 6/15/12 12:00 AM 6/16/12 12:00 AM Ozone (ppb) 

## June 13

- 16, 2012 Ozone

South Pass

Boulder

Daniel

Pinedale

Big Piney

Juel Spring

Yellowstone

Grand TetonP a g e | 19

Data QA/QC and Equipment Quality Assurance/Quality Control procedures were followed in accordance with 40 CFR Part 58, Appendix A, Section 3.2 Measurement Quality Checks of Automated Methods and the Quality Assurance Project Plan for the Boulder and Big Piney monitoring project s

. During second and fourth quarters of 2012, Technical & Business Systems, Inc. 11 conducted independent performance audit s of the ozone analyzer s at Boulder and Big Piney ( refer to Table 2 ). All tests met WDEQ/AQD specified data quality objectives, which are consistent with QA Handbook Vol II, Section 3.0

, Revision No: 1

.

Table 2. 2 nd and 4 th quarter audit statistics for 2012 for Big Piney and Boulder.

2012 Big Piney Ozone Audit Results

Slope Correlation Y

- Intercept Audit Point % Difference April 1 9 0.9 69 0.9999 0.000 Point 2 = 0

. 0 % Point 3 = - 2

. 5 % Point 4 = - 3.3 % November 1 1 0.9 88 1.0000

- 0.001 Point 2 = - 2.7 % Point 3 = - 2.4 % Point 4 = - 1. 6 %

2012 Boulder Ozone Audit Results

Slope Correlation Y

- Intercept Audit Point % Difference April 1 7 0.9 50 1.0000 0.00 0 Point 2 = - 2.9 % Point 3 = - 4.9 % Point 4 = - 4.9 % November 1 5 0.9 80 1.0000

- 0.001 Point 2 = - 5.3 % Point 3 = - 3.6 % Point 4 = - 2.2 %
Statistical Analysis A basic method for portraying the statistical significance of the June 14 , 2012 elevated ozone event is via a histogram. A histogram shows the frequency of occurrence of individual values, and often it takes the shape of a “Bell Curve” or “normal distribution”. Figure s 7 and 8 show t he 1

- hour average and daily maximum 8

- hour ozone for the Boulder and Big Piney ozone monitor s for each June from 200 5

- 2012 (Boulder) and from 2011

- 2012 (Big Piney)

, respectively. Note that the bell curve is elongated to the right where the June 14 , 2012 Boulder and Big Piney elevate d ozone concentration s reside. The daily 8

- hour maximum ozone histograms clearly show that the June 14, 2012 data points represent data of statistical significance.

11 Please refer to Appendix H for the 2 nd and 4 th Quarter 2012 QA Audit Reports.P a g e | 20

Figure 7

. Histogram s of Junes 2005

- 2012 for Boulder . Click image s to enlarge.

Figure 8

. Histogram s of Junes 2011

- 2012 for B ig Piney

. Click image s to enlarge.

An additional statistical measure of the significance of the June 14 , 2012 Boulder and Big Piney elevated ozone event is by means of a simple t

- test 12 between two means. A high t

- test score and very low p

- value 13 , shown in Table 3

, indicate that the June 14 , 2012 event was statistically significantly higher when compar ed to ozone values observed during June s of other years.

I f one analyzes the June 14, 2012 event from a cumulativ e percentage perspective, the Big Piney and Boulder daily maximum 8

- hour average ozone values of 77 and 76 reside in the greater than 99 th percentile for June 20 05

- 2012 (Boulder) and 2011

- 2012 (Big Piney) (refer to Table 4).

12 For further information on t

- tests, please consult: http://www.statsoft.com/textbook/basic

- statistics/#t

- test for independent samples . Note to reader: the WDEQ does not endorse any private business or its p roducts. The aforementioned site is for informational purposes only.
13 For further information on p

- values, please consult: http://www.statsoft.com/textbook/elementary

- concepts

- in

statistics/#What is "statistical significance" (p

- level) . Note to reader: the WDEQ does not endorse any private business or its products. The aforementioned site is for informational purposes o nly.P a g e | 21

Table 3. Boulder and Big Piney t

- test and p

- value statistics for 1

- hour average ozone for Junes of 2005

- 2012 and 2011

- 2012 , respectively

.

Dates Statistic

Number of Samples Arithmetic Mean Standard Deviation June 200 5

- 2012 5,181 44.30 1 3

. 30

Boulder J une 14

, 2012 9 75.56 3

. 17

t

- test= 29.61 p

- value=0.0 000

Dates Statistic

Number of Samples Arithmetic Mean Standard Deviation June 2011

- 2012 1,272 42.43 13.90

Big Piney June 14, 2012 7 79.14 4.74

t

- test=20.49 p

- value=0.0000

Table 4. Big Piney and Boulder 99 th and greater percentile for June 14, 2012 event. Site Daily 8

- Hour Maximum Ozone Count Cumulative Percent Big Piney 77 1 100.0000 Boulder 76 1 99.2958

A final m eans of di splay ing the June 14

, 2012 Boulder and Big Piney elevated ozone values as being statis tically significantly higher is by a “box

- and

- whisker” plot. Figure 9 shows how to int erpret a “box

- and

- whisker” plot. Figure s 10 and 1 1 show t hat the June 14 , 2012 Boulder and Big Piney 1

- h our average and daily maximum 8

- hour ozone concentrations are greater than the 75 th percentile concentration value, approaching the “ data outlier” range when compared to all June data from Boulder (2005

- 2012) and Big Piney ( 20 1 1

- 201 2 )

. The daily maximum 8

- hour ozone data for Boulder and Big Piney are statistical data “outliers” and are statistically significantly higher than the rest of the data.

Figure 9

. D escri ption of how to interpret a Box

- and

- Whiskers plot (Image courtesy Sonoma Technology, Inc.)

. Click image to enlarge.P a g e | 22

Figure 10

. Box

- and

- whiskers plot of Junes 2005

- 2012 for Boulder. Click images to enlarge.

Figure 1 1

. Box

- and

- whiskers plot of Junes 20 11

- 2012 for B ig Piney

. Click images to enlarge.P a g e | 23

Supporting Meteorological Data: Weather Overview The NARR depicts 14 a vigorous upper level disturbance over Washington at 8 am MST June 13, 2012 (refer to Figure 1 2 ). Throughout June 13, 2012, the disturbance moved east and arrived at central Idaho at 5 pm on June 13, 2012 (refer to Figure 1 3 ). By 2 am MST June 14, 2012, the upper level disturbance was over the Wyoming

- Montana border (refer to Figure 1 4 ).

Figure 1 2 . North America Reanalysis valid at 8 a m MST, June 13, 2012 . Click image to e nlarge. Click here for a time animation from 11 pm MST June 12 to 5 pm MST June 14, 2012. Graphic courtesy Fred Gadomski and the Penn State U niversity Department of Meteorology.

Figure 1 3 . North America Reanalysis valid at 5 p m MST, June 13, 2012

. Click image to enlarge. Graphic courtesy Fred Gadomski and the Penn State University Department of Meteorology.

14 Please refer to Appendix C to learn how to interpret the NARR.P a g e | 24

Figure 1 4

. North America Reanalysis valid at 2 a m MST, June 14, 2012

. Click image to enlarge. Graphic courtesy Fred Gadomski and the Penn State University Department of Meteorology.

Supporting Meteorological Data : GOES Total Column Ozone Data Because of the upp er air disturbance and associated SI, an enhanced green area (increased Dobson values) can be seen in the hourly GOES total column ozone data over Washington at 11
pm MST June 12 , 2012 (refer to Figure 1 5 ) . Figure 1 6 shows a dark

- green area over north central Idaho with lighter shades of green over central Idaho extending southward to northeast Nevada at 10 am MST June 13, 2012. The enhanced green areas were associated with t he upper level storm system and higher Dob son values

, providing additional evidence of an SI event that affected Wyoming. (Note to reader: GOES Band

- 12 data was unavailable during this time).

Figure 1 5 . GOES Total Column Ozone (DU) for 11 p m MST June 12, 2012 . Click to i mage to e nlarge. Click here for a time animation from 5 am MST June 13 to 11 am MST June 14, 2012. Image courtesy of the Data Center at the Sp ace Science and Engineering Center (SSEC) of the University of Wisconsin

– Madison.P a g e | 25

Figure 1 6 . GOES Total Column Ozone (DU) for 10 a m MST June 13, 2012 . Cl ick to i mage to e nlarge. Image courtesy of the Data Center at the Space Science and Engineering Center (SSEC) of the University of Wisconsin

– Madison

.

Supporting Meteorological Data : AIRS Satellite Measurements of Carbon Monoxide As mentioned in the introduction of this package, stratosperhic air contains little CO (Pan, Randel, et al. 2004 ; New ell, et al. 1999; Stoller, et al. 1999 )

. AIRS 15 satellite measurements of total column CO and CO at 618 mb (approximate level of the SI) show lower CO concentrations

over western Wyoming on June 14 , 2012 (refer to Figure s 17

- 18 , respectively ). The realtiv ely lower concentration of CO over western Wyoming is another piece of evidence of an SI event having affected western Wyoming.

Figure 17. AIRS satellite derived total column CO for June 14, 2012

. Figure courtesy the Giovanni online data system, developed and maintained by the NASA GES DISC

.

15 For more information on AIRS satellite data, please visit this website: http://airs.jpl.nasa.gov/

.P a g e | 26

Figure 18. AIRS satellite derived CO at 618 mb (descending pass) for June 14, 2012. Figure courtesy the Giovanni online data system, developed and maintained by the NASA GES DISC

.

Supporting Meteorologica l Data: Isentropic Potential Vorticity, Relative Humidity, and Potential Temperature Vertical Cross

- Sections S tratospheric air can be “tagged” by identifying areas characterized by approximately greater than or equal to 1

- PVU, dry air, and tightly packed ( and sloping) isolines of PT. Using the 20

- km RAP model 0

- hour analyses, a descending SI can be illustrated by examining atmospheric vertical cross

- sections over a time range. One can visualize an SI approaching the earth’s surface by observing the temporal and vertical evolution of the greater than 1

- PVU isoline, dry air, and the pattern of PT isolines superimposed on a cross

- section of the earth’s terrain.
Figure 1 9 shows the line used to create a north

- south cross

- section over Idaho. As the upper level system moved over Idaho during the day, an SI descended (as shown by the descending red isoline of greater than 1

- PVU, less than 15% RH area, and sloping P T isolines) over central Idaho as depicted b y Figures 20

- 2 2 . Note that less than 15% relative humidity air and tightly packed isolines of PT coincide with the descending 1

- PVU red isoline throughout June 13, 2012. The 1

- PVU isoline descended to between 3 200 and 3800 mean sea level ( msl ) ( refer to bottom graphic of Figure 22 )

. These cross

- sections provide further evidence of an SI having occurred over central Idaho during June 13, 2012.P a g e | 27

Figure 1 9

. Map view of terrain, IPV, RH, and PT cross

- section.

Figure 20 . RAP 20

- km, 0

- hour analysis showing s outh

- to

- north cross

- section (left

- to

- right) terrain (solid dark line), IPV (colored contours starting at 1

- PVU), RH (shaded areas depicting RH values less than 15%), and PT (thin
black contours ) cross

- sect ion valid at 9 am MST, June 13, 2012. Click image to enlarge. Click here for a time animat ion from 5 am MST June 13 to 11 am MST June 14, 2012. Data below terrain not real.P a g e | 28

Figure 21

. RAP 20

- km, 0

- hour analysis showing s outh

- to

- north cross

- section (left

- to

- right) terrain (solid dark line), IPV (colored contours starting at 1

- PVU), RH (shaded areas depicting RH values less than 15%), and PT (thin black contours ) cross

- section valid at 5 p m MST, June 13, 2012. Click image to enlarge. Data below terrain not real.P a g e | 29

Figure 22

. Top: RAP 20

- km, 0

- hour analysis showing s outh

- to

- north cross

- section (left

- to

- right) terrain (solid dark line), IPV (colored contours starting at 1

- PVU), RH (shaded areas depicting RH values less than 15%), and PT (thin black contours ) cross

- section valid at 7 p m MST, June 13, 2012. Bottom: RAP 0

- hour analysis showing IPV

cross - section valid at 7 pm MST June 13,2 012 with altitude in msl on the vertical axis. Click top image to enlarge. Dat a below terrain not real.P a g e | 30

Supporting Meteorological Data : Back Trajectory Analysis While cross

- section analysis confirms an SI having occurred over central Idaho, a trajectory analysis is warranted to examine the path the ozone

- rich a ir took from the SI to the UGRB. As already shown by Figure 22 , the SI descended to between 3200 and 3800 msl over central Idaho. Therefore, a trajectory analysis was performed using the central Idaho location as a start/endpoint of air parcel trajectori es. Forward and backward trajectory analyses occurred using the HYSPLIT program with archived NAM 12

- km data from June 13

- 14, 2012. Instead of analyzing one trajectory, t he option of using HYSPLIT in ensemble mode was chosen to provide a more realisti c li kelihood of the air’s pathway. Figure 2 3 shows backward trajectories emanating at 2600 msl over the UGRB for 1 1

a m MST June 14, 2012 and ending over central Idaho near the SI at 5 pm MST June 13, 2012

. Figure 2 3 is further evidence of air originating from the SI and arriving at the UGRB around the same time elevated ozone values were observed.
Figures 2 4

- 2 5 portra y forward trajectories starting at 3600 and 3200 at 5 pm MST June 13, 2012 over central Idaho and end ing at 10 am MST June 14, 2012

, respectively. Figure 2 6 shows forward trajectories starting at 3700 msl at 6 pm MST June 13, 2012 and ending at 10 am MST June 14, 2012

. From Figures 2 4

- 2 6 , it is apparent that air parcels emanating from the SI over Idaho arrived at the UGRB approximately the same time 1

- hour average ozone values started to increase; further evidence of air of SI origin having affect ed ozone monitors in the UGRB.P a g e | 31

Fig ure 2 3

. Top: map view of e nsemble of back trajectories starting at the middle of the UGRB at 1 1 am MST June 14, 2012 and ending at 5 pm M S T June 13, 2012 . Starting trajectories height : 2600 msl

. Bottom: vertical profile of back trajectories (height is agl)

. Click i mage s to e nlarge.P a g e | 32

Fig ure 2 4

. Top: map view of c entral Idaho ensemble of forward trajectories emanating from 3600 msl starting at 5 pm MST June 13, 2012 and ending at 10 am MST June 14, 2012. Bottom: vertical profile of back trajectories. (height is agl) Click i mage s to e nlarge.P a g e | 33

Fig ure 2 5

. Top: map view of c entral Idaho ensemble of forward trajectories emanating from 3200 msl starting at 5 pm MST June 13, 2012 and ending at 1 0 am MST June 14, 2012. Bottom: vertical profile of back trajectories. (height is agl) Click i mage s to e nlarge.P a g e | 34

Fi g ure 2 6

. Top: map view of c entral Idaho ensemble of forward trajectories emanating from 3700 msl starting at 6 pm MST June 13, 2012 and ending at 1 0 am MST June 14, 2012. Bottom: vertical profile of back trajectories. (height is agl) Click i mage s to e nlarge.P a g e | 35

Supporting Meteorological Data : SI

- Composite Chart Another means of showing the SI event is by showing an “SI composite chart” of IPV, RH, and daily maximum 8

- hour surface ozone data . This “quick look chart” is an easy way to visualize IPV, RH, and surface ozone on one chart. Figure 2 7 shows the 0

- hour RAP 20

- km analysis of the 500 mb height patter n , greater than 1

- PVU

, and relative humidity less than 3 0 % at 6 25 mb (approximate height of the SI) valid at 6 am MST, June 13 , 2012. Superimpose d on the chart is EPA’s AQS daily maximum 8

- hour ozone greater than 6 0 ppb. Figure 2 8 displays the same aforementioned parameters valid at 1 0 am MST, June 13 2012 while Figure 2 9 sh ows the same information valid at 12 pm June 13 , 2012. The noteworthy aspe ct of the “S I composite chart” is that at 10 am MST, June 1 3 , 2012 and 12 p m June 1 3 , 2012 , all of the parameters are juxtaposed on one another. Specifically, the greater than 1

- PVU area is coincident with RH values less than 3 0% aiding in producing the greater than 70 ppb maximum (“bulls

- eye”) over eastern Idaho and extreme western Wyoming. Coincident with the aforementioned juxtaposition

, the ozone monitor at Grand Teton National Park (located in northwestern Wyoming) experie nce d elevated 1

- hour average ozone a s shown in Figure 5

. On June 14, 2012, the SI

- composite charts valid at 4 am and 11 am MST (Figures 30 and 31 ) show the same pattern as was mentioned in the previous paragraph: a greater than 1

- PVU area with less than 30% RH juxtaposed on a “bulls

- eye” of greater than 75 ppb.
The “SI composite chart” provides further evidence of an SI causing an increase in surface

ozone.

Figure 2 7

. 6 am MST, June 13, 2012 RAP 20

- km, 0

- hour analysis of 500 mb heights in meters (solid black) , 6 25 mb IPV >= 1

- PVU blue isolines , 6 25 mb RH <= 3 0% in grey, and EPA AQS Daily Max 8

- hour O3 in ppb >= 6 0 ppb in colored shading

. Click i mage to e nlarge.P a g e | 36

Figure 2 8

. 10 am MST, June 13, 2012 RAP 20

- km, 0

- hour analysis of 500 mb heights in meters (solid black) , 6 25 mb IPV >= 1

- PVU blue isolines , 6 25 mb RH <= 3 0% in grey, and EPA AQS Daily Max 8

- hour O3 in ppb >= 6 0 ppb in colored shading

. Click i mage to e nlarge.

Figure 2 9

. 12 p m MST, June 13, 2012 RAP 20

- km, 0

- hour analysis of 500 mb heights in meters (solid black) , 6 25 mb IPV >= 1

- PVU blue isolines , 6 25 mb RH <= 3 0% in grey, and EPA AQS Daily Max 8

- hour O3 in ppb >= 6 0 ppb in colored shading

. Click i mage to e nlarge.P a g e | 37

Figure 30

. 4 am MST, June 1 4 , 2012 RAP 20

- km, 0

- hour analysis of 500 mb heights in meters (solid black) , 6 25 mb IPV >= 1

- PVU blue isolines , 6 25 mb RH <= 3 0% in grey, and EPA AQS Daily Max 8

- hour O3 in ppb >= 6 0 ppb in colored shading

. Click i mage to e nlarge.

Figure 31

. 11 am MST, June 1 4 , 2012 R AP 20

- km, 0

- hour analysis of 500 mb heights in meters (solid black) , 6 25 mb IPV >= 1

- PVU blue isolines , 6 25 mb RH <= 3 0% in grey, and EPA AQS Daily Max 8

- hour O3 in ppb >= 6 0 ppb in colored shading

. Click i mage to e nlarge.P a g e | 38

Supporting Meteorological Data : Vertical mixing as shown by lapse rates An additional method for depicting a well

- mixed atmosphere supportive of vertically transporting air of SI origin to the earth’s surface is by means of mid

- tropospheric lapse rate analysis. By showing the juxtaposition of 7 0 0

- 5 0 0 mb environmental layer lapse rates (ELR’s) and greater than 1

- PVU at 6 25 mb, one can visualize conditions conducive for vertical mixing up to the SI . As the magnitude of the ELR start s to approach the dry adiabatic lapse rate of 9.8o C km

- 1 ( D A LR ) , the atmosphere is better able to mix in the vertical. Figure 32 shows an axis (blue isolines) of greater than 1

- PVU over southern Idaho and a “ bulls

- eye” of greater than 1

- PVU over west central Wyoming at 3 am MST June 14, 2012. At 11 am MST June 14 , 2012

, Figure 33 shows two “bulls

- eyes” over western Wyoming of greater than 1

- PVU superimposed with ELR’s ranging from 6 to 8o C km

- 1. At 12 pm MST June 12, 2012, a greater than 1

- PVU “bulls

eye” was near Big Piney and Boulder coincident with ELR’s from 6 to 8 o C km

- 1 (refer to Figure 3 4 )

. From early morning to midday of June 14 , 2012, the ELR increased in magnitude and assisted the SI air to re ach the vicinity of the Boulder and Big Piney ozone monitors. This is additional evidence of ozone rich air from the central Idaho SI having been able to mix to the ground creating elevated ozone values.

Figure 32

. 7 0 0

- 5 0 0 mb lapse rate and 6 25 mb IPV im age at 3 am MST, June 14 , 2012 RAP 20

- km, 0

- hour analysis . Lapse rate units are degrees C km

- 1. IPV units are potential vorticity units. Click i mage to e nlarge.
Click here for a time animation from 2 am to 1 pm MST June 14, 2012.P a g e | 39

Figure 3 3

. 7 0 0

- 5 0 0 mb lapse rate and 6 25 mb IPV image at 11 am MST, June 14 , 2012 RAP 20

- km, 0

- hour analysis . Lapse rate units are degrees C km

- 1. IPV units are potential vorticity units. Click i mage to e nlarge.

Figure 3 4

. 7 0 0

- 5 0 0 mb lapse rate and 6 25 mb IPV image at 12 p m MST, June 14 , 2012 RAP 20

- km, 0

- hour analysis . Lapse rate units are degrees C km

- 1. IPV units are potential vorticity units. Click i mage to e nlarge.P a g e | 40

Supporting Meteorological Data : Upper Air RAOB’s Recall that a lowering of the tropopause or the existence of a dry air layer is another indication of a stratospheric air. By examining the June 13

- 14, 2012 RAOB’s from Boise, Idaho, Great Falls, Montana, and Riverton, Wyoming, one can detect the presence of SI

- air. The 5 am MST June 13, 2012 Boise RAOB shows a dry air layer from 600 to 500 mb (Figure 3 5 ). At 5 pm MST June 13, 2012, the Boise RAOB shows that the dry air layer was between 675 and 575 mb (Figure 3 6 ). Meanwhile, the 5 am MST June 14, 2012 Riverton RAOB portrays the dry air layer between 650 and 550 mb as shown by Figure 3 7 . By 5 pm MST June 14, 2012, the Great Falls and Riverton RAOB’s show the dry air layer between 650

- 600 mb and 700

- 500 mb

, respectively (Figures 3 8 and 3 9 ).
Figures 3 6 and 3 8

- 3 9 show that the atmosphere was well

- mixed (as shown by th e dry adiabatic lapse rate (DALR)) vertically up to the ozone

- laden, dry air layer providing another piece of evidence that supports air from an SI having vertically mixed to the earth’s surface.

Figure 3 5

. Boise, Idaho RAOB at 5 a m MST, June 13, 2012. C lick i mage to e nlarge. Image courtesy Plymouth State University Department of Atmospheric Science & Chemistry.P a g e | 41

Figure 3 6

. Boise, Idaho RAOB at 5 p m MST, June 13, 2012. Click i mage to e nlarge. Image courtesy Plymouth State University Department of Atmospheric Science & Chemistry.

Figure 3 7

. Riverton, Wyoming RAOB at 5 a m MST, June 14, 2012. Click i mage to e nlarge. Image courtesy Plymouth State University Department of Atmospheric Science & Chemistry.P a g e | 42

Figure 3 8

. Great Falls, Montana RAOB at 5 p m MST, June 14, 2012. Click i mage to e nlarge. Image courtesy Plymouth State University Department of Atmospheric Science & Chemistry.

Figure 3 9

. Riverton, Wyoming RAOB at 5 p m MST, June 14, 2012. Click i mage to e nlarge. Image courtesy Plymouth State University Department of Atmospheric Science & Chemistry.P a g e | 43

Supporting Meteorological and Ambient Data : Surface

- based data

Figure s 40

- 4 1 show the June 13

- 15 , 2012 1

- hour average ozone and hourly relative humidity data for the Big Piney and Boulder monitors

. The data show a decrease in relative humidity that coincided with an increase in 1

- hour average ozone values. Recall that air of stratospheric origin is dry as depicted by very sma ll relative humidity values. An increase in ozone concentration and a decrease in relati ve humidity at Big Piney and Boulder is further evidence of an SI event having occurred on June 14 , 2012 16

.

It has been documented (T. S. ENVIRON 2008) that elevated ozone values can occur at the UGRB ozone monitors of Boulder, Big Piney, Pinedale, Daniel, and Juel Spring because of light winds, snow cover, and strong inversions during the January

- March winter ozone season. However, d uring the June 14, 2012 period of elevated ozone, strong winds (refer to Figure 42 ) buffeted the UGRB prior to the SI event, and no snow cover or strong inversions were present. Accumulation of surface

- based ozone precursors did not occur because meteorol ogical conditions were not supportive of precursor buildup prior to elevated ozone readings.

Figure 40

. June 13

- 15, 2012 Big Piney ozone and relative humidity.

16 Please refer to Appendices D

- G for the complete AQS dataset including all air quality and meteorological parameters for June 13

- 16, 2012. 0 10 20 30 40 50 60 70 80

0 10 20 30 40 50 60 70 80 90

6/13/12 12:00 PM 6/14/12 12:00 PM 6/15/12 12:00 PM Relative Humidity (%) Ozone (ppb) 

## Big Piney 1

- Hour Average Ozone and

Relative Humidity

Ozone

RHP a g e | 44

Figure 41

. June 13

- 15, 2012 Boulder ozone and relative humidity

.

Figure 42

. June 13

- 15, 2012 S outhwest Wyoming surface wind speeds. 0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70 80 90

6/13/12 12:00 PM 6/14/12 12:00 PM 6/15/12 12:00 PM Relative Humidity (%) Ozone (ppb ) 

## Boulder 1

- Hour Average Ozone and Relative

Humidity

Ozone

RH

0 2 4 6 8 10 12 14 16 18 20

6/13/12 12:00 PM 6/14/12 12:00 PM 6/15/12 12:00 PM Wind Speed (m/s) 

## June 13

- 15, 2012 Wind Speed

South
Pass

Boulder

Daniel

Pinedale

Big Piney

Juel SpringP a g e | 45

Lastly

, NO 2 plays an important role in ozone formation. Without attempting to quantify NO 2 levels as they pertain to resultant ozone levels, a relative comparison of NO 2 levels can be made. Figure 4 3 depicts June 13

- 15, 2012 NO 2 for South Pass, Boulder, Daniel, Pinedale, Big Piney, and Juel Spring. With the exception of Pinedale, 1

- ho ur average NO 2 levels ranged between 0 and 2 ppb ; near the detection level of the instrum ent

. Figures 4 4 and 4 5 present the month of June 2012 and June 14, 2012 Pinedale hourly NO 2 , respectively. June 14, 2012 is representative of the diurnal cycle observed during the entire month of June. Furthermore, Figures 4 6 and 4 7 show the distributio n ( Box

- and

- whiskers plots ) of 2009

- 2012 and June 2012 Pinedale hourly NO 2 values from midnight to 11 pm MST, correspondingly. O n both box

- and

- whiskers plots , NO 2 concentration increases during the early morning hours, decreases late in the morning, and increases during mid

- evening. The June 14, 2012 hourly NO 2 displays a similar pattern compared to Figures 4 6 and 4 7

.

Figure 4 3

. June 13

- 15, 2012 S outhwest Wyomin g NO 2 .

0 5 10 15 20 25 30 35

6/13/12 12:00 PM 6/14/12 12:00 PM 6/15/12 12:00 PM NO 2 (ppb) 

## June 13

- 15, 2012 NO 2

South
Pass

Boulder

Daniel

Pinedale

Big Piney

Juel SpringP a g e | 46

Figure 4 4

. June 2012 Pinedale hourly NO 2 .

Figure 4 5

. June 14, 2012 Pinedale hourly NO 2 . 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

6/1/12 12:00 AM 6/16/12 12:00 AM 7/1/12 12:00 AM NO 2 (ppb ) 

## June 2012 Pinedale Hourly NO 2

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

12:00 AM 3:00 AM 6:00 AM 9:00 AM 12:00 PM 3:00 PM 6:00 PM 9:00 PM 12:00 AM NO 2 (ppb ) 

## June 14, 2012 Pinedale Hourly NO 2P a g e | 47

Figure 4 6

. 2009

- 2012 Pinedale box

- and

- whiskers plots of hourly NO 2 values from midnight to 11 pm MST. Click i mage to e nlarge.

Figure 4 7

. June 2010

- 2012 Pinedale box

- and

- whiskers plots of hourly NO 2 values from midnight to 11 pm MST. Click i mage to e nlarge.P a g e | 48

SUMMARY AND CONCLUSIONS During the interval from late winter to late spring in the northern hemisphere, weather producing systems (i.e. tropospheric storm systems, upper level disturbances or upper level storm systems) aid in causing the tropopause to “fold” or descend into the troposphere where our weather occurs. Tropopause folding permits ozone

- rich air from the stratosphere to enter the troposphere, also called a stratospheric intrusion (SI), creating the potential for ground level ozone monitors over the higher terrain of the western United States to experience elevated readings.
Throughout June 13

- 14, 2012, an upper atmospheric disturbance associated with an SI moved over central Idaho injecting ozone

- rich air into the troposphere. The ozone

- laden air then moved over western Wyoming creating elevated ozone readings resulting in 8

- hour ozone standard exceedances of 76 and 77 ppb at the Boulder and Big Piney, Wyoming ozone monitors respectively.
Additionally, the Yellowstone and Grand Teton National Park ozone monitors as well as the AQD ozone monitors at South Pass, Daniel, Pinedale, and Juel Spring measured elevated 1

- hour average ozone values from the upper 60’s to upper 70’s ppb during the SI event (refer to Figure 5). (Note to reader: the Pinedale CASTNET site was not operational during June 2012 due to a prolonged power outage).

It has been documented (T. S. ENVIRON 2008) that elevated ozone values can occur at the UGRB ozone monitors of Boulder, Big Piney, Pinedale, Daniel, and Juel Spring because of light winds, snow cover, and strong inversions during the January

- March winter ozon e season. However, during the June 14, 2012 period of elevated ozone, strong winds (refer to Figure 39) buffeted the UGRB prior to the SI event, and no snow cover or strong inversions were present. Accumulation of surface

- based ozone precursors did not o ccur because meteorological conditions were not supportive of precursor buildup prior to elevated ozone readings.
Statistical analyses performed on the Boulder and Big Piney data show that the June 14, 2012 ozone data w as statistically significantly higher than values recorded during June of each year starting from 2005

- 2012 (Boulder) and 2011

- 2012 (Big Piney). The AQD performed a careful evaluation of the June 14, 2012 episode, and is confident that the Boulder and Big Piney event presented in this document is the result of a stratospheric intrusion.

The “ Supporting Meteorological Data” sections o f this document clearly show that an upper atmospheric disturbance and its attendant SI carried ozone

- rich air from the strat osphere over central Idaho to the area around the Boulder and Big Piney ozone monitor s during the June 13

- 14 , 2012 . Due to the disturbance, tropospheric conditions were conductive for vertical mixing over the Boulder and Big Piney area as evidenced by the “ Backward and Forward Trajectory Analyses ” , “ Vertical mixing as shown by lapse rate analysis ”, and “ Upper Air RAOB’s ” section s of this document. As a result, 1

- hour average ozone values at the Boulder and Big Piney ozone monitor s increased during June 1 4 , 2012

. The SI meets the definition of a stratospheric intrusion as outlined in the preamble to “Treatment of Data Influenced by Exceptional Events” 40 CFR Parts 50 and 51 section IV(D)(5)(e). Specifically, air originated in the stratosphere and was tr ansported directly to the earth’s surface via an upper level disturbance causing the Boulder and Big Piney June 14 , 2012 exceptionalP a g e | 49

event. This event meets the specific criterion established in 40 CFR 50.14 (3)(iii) as described below.

Criteria (A) states that “[t]he event satisfies the criteria set forth in 40 CFR 50.1(j)”:
40 CFR 50.1 (j) requires that an exceptional event “affects air quality, is not reasonably controllable or preventable...” and is a “...natural event[s]”. The Exceptional Event s Rule Preamble and the 40 CFR 50 Appendices I & P specifically list stratospheric intrusion of ozone

as a natural event that could affect ground level ozone concentrations. This packet includes data and graphics that display a weather disturbance

, and cl early show an intrusion of stratospheric air that affected ambient air quality during June 14, 2012 at the Boulder and Big Piney ozone monitors

.
Criteria (B) states that “ [ t ] here is a clear causal relationship between the measurement under consideration a nd the event that is claimed to have affected the air quality in the area ” :

The causal relationship is a basic one in which the ozone standard exceedance w as cau sed by tropospheric folding resulting in an SI. For the exceedance s that occurred on June 14, 2012 an intrusion of stratospheric air occurred over central Idaho upwind of the Boulder and Big Piney monitors, and injected ozone

- rich air into the area above and surrounding the Boulder and Big Piney ozone monitor s. The causal nature of the SI’s impact on ozone values at the Boulder and Big Piney ozone monitors is further supported by the corroboration of ground

- based air quality data to the spatial and temporal accuracy of the meteorological analysis.

Criteria (C) states that “ [ t]he even t is associated with a measured concentration in excess of normal historical fluctuations, including background”:

Statistical analysis of June 14, 2012 data clearly shows that the exceptional event was statistically significantly higher than data recorded during prior months of June from 2005

- 2012 (Boulder) and 2011

- 2012 (Big Piney)

.

Criteria (D) states that “[t]here would have been no exceedance or violation but for the event”:

Th e SI allowed ozone

- rich air to descend to the Boulder and Big Piney ozone monitor s creating

e levated 1

- hour average ozone values. The exceedances of the ozone National Ambient Air Quality Standards ( NAAQS ) would not have occurred “b ut for” the SI.

T he 75 th percentile hourly ozone concentrations doe s not exceed 55 ppb for the month of June for the years tested (200 5/11

- 20 12 ) for statistical significance . Hourly concentrations monitored during June 14, 2012 were outliers for the months of June 2005

- 2012 (Boulder) and 2011

- 2012 (Big Piney)

. Statistic s demonstrating that ozone levels were unusually elevated affirm that the exceedance s of the ozone National Ambient Air Quality Standards (NAAQS) would not have happened “but for” the SI event having occurred during June 14, 2012.
In brief, the WDEQ/AQD co ncludes that an SI occurred during June 13

- 14, 2012 resulting in an exceptional event. This exceptional event has passed the four criterion tests under 40 CFR 50.14 (3)(iii). Consequently, the WDEQ/AQD is requesting for EPA concurrence that the event wasP a g e | 50

exceptional and for the exclusion from the Air Quality System (AQS) database of the Big Piney and Boulder 1

- hour average oz one data for the following times:

Table 5

. Big Piney and Boulder times and dates for AQS data exclusion.

Site Begin Time/Date(s) End Time/Date(s) Big Piney 0900 MST June 14, 2012 1900 MST June 14, 2012 Boulder 09 00 MST June 14, 2012 21 00 MST June 14, 2012P a g e | 51

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- horizontal layers in the troposphere." Nature. Vol. 398. 1999. 316

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- A Case Study." Physics and Chemistry of the Earth 26, no. 10 (2001): 801

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Wimmers, Anthony J., et al. "Signatures of tropopau se folding in satellite imagery." Journal of Geophysical Research 108, no. D4 (2003): 8/1

- 8/11.P a g e | 54

APPENDIX A

- Documented Stratospheric Intrusion Events

March 12, 1978

Much of the literature regarding SI’s refers to Shapiro’s May 1980 paper outlin ing the results of a research flight that flew through an SI on March 12, 1978 (Shapiro 1980) . Equipped with a “fast

- response ozone” analyzer, a research plane flew several transects through an SI over California. Shapiro produced vertical cross

- sections of IPV, PT, and O 3 concentration from the flight data. Figures A and B portray cross

- sections of IPV, PT, and the flight track and clearly show that the O 3 concentration increased when the plane flew through the SI.

Figur e A. Cross

- section through the 5 pm MST March 13, 1978 tropopause folding event. Potential temperature (K) thin solid lines; wind speed (meters per second) heavy dashed lines; flight track, thin dashed lines; the 100 x 10

- 7 K mb

- 1 s

- 1 potential vorticity Tropopause (1

- PVU), heavy solid line; troposphere, stippled area. Click i mage to enlarge. Figure courtesy Mel Shapiro per personal communication.

Figure B. Cross

- section through the 5 pm MST March 13, 1978 tropopause folding event. Ozone concentra tion analysis, parts per hundred million by volume (pphm/vol). Analysis for upper flight track data, dotted lines; lower flight track analysis, solid lines; tropopause, interfaces between stipple and cl ear area. Click i mage to

e nlarge. Figure courtesy M el Shapiro per personal communication.P a g e | 55

November 7

- 8, 1999

During 1999, the Mesoscale Alpine Programme captured an SI event over northern Italy from evidence obtained by using remote optical sensing technology known as the Raman Light Detection And Ranging (LIDAR) sensor (Aulerio, et al. 2005) . The Raman LIDAR measures water vapor concentration, and combined with back trajectory analyses, an SI was detected which descended to 4 km AMSL and was ~500 meters thick in 1999 o ver northern Italy. In other words, the SI lowered to within 16,000 feet of the earth’s surface and extended over the length of five football fields upward.

April 28, 2008

During 2008, the Stratosphere

- Troposphere Analyses of Regional Transport (START08) field project utilized a research aircraft to measure a multitude of ambient air quality and meteorological parameters (L. L. Pan 2010) . On April 28, 2008, Research Flight 4 penetrated the upper portion of an SI , which occurred over northern Missouri (refer to Figure C). Data from the flight reveals more direct evidence that O 3 concentrations increased as the plane entered the SI. Figure D shows the height of the flight path, and a cross

- section with corresponding flight times, IPV, and PT as the plane entered the SI. As the plane penetrated the SI, the O 3 concentration increa sed to over 400 ppb, CO decreased, PT increased, and the RH decreased providing further evidence of an SI as evidenced by Figures E and F.

Figure C. Thin red line in plan

- view is the flight path. Click i mage to e nlarge.

Figure D. Cross

- section of fl ight pat h and IPV. Times are in MDT. Click image to enlarge.P a g e | 56

Figure E. Time series of ozone, carbon monoxide, and relative humidity dur ing flight. Times are in MDT. Click i mage to e nlarge.

Figure F. Time series of ozone and potential temperature plotted. Times are in MDT

. Click i mage to e nlarge.P a g e | 57

APPENDIX B

- Diagnosis Example
Event : March 26, 2006 SI moving ov er Colorado ground based ozone monitors

. Between March 25, 2006 and March 27, 2006, a strong upper level system moved ove r Colorado and Wyoming. Air closest to the ground was well mixed due to winds associated with the movement of the weather system across the region. A well

- mixed environment enhances the likelihood that stratospheric air can “mix

- down” to the surface. In this instance, an SI associated with the passing weather disturbance injected ozone

- rich air into the area resulting in abnormally high hourly ozone readings. Figure A shows several Colorado ozone monitors “spiking” well into the 70’s and lower 80’s ppb during the morning of March 26, 2006 for 1

- hour average

ozone.

Figure A

. Various Colorado and Wyoming 1

- hour average Ozone concentrations (ppb) from March 24

- 27, 2006 (Note: Ti me in Mountain Standard Time). Click i mage to e nlarge.

Supporting Meteorological Data: Weather Overview The NARR for March 25

- 27, 2006 shows that an upper level weather system moved over Colorado. Figure B is a 4

- panel graphic of 500 mb heights and vorticity, 700 mb heights and relative humidity, 850 mb heights/temperatures/relative humidity, and the surfac e pressure pattern at 11 am MST on March 26, 2007 (Please refer to Appendix C for a further explanation on how to interpret the NARR charts). Note the 500 mb circulation center over Colorado and Wyoming. Recall that upper level weather systems aid in tro popause folding, or the descent of

ozone

- rich air into the troposphere. Time stamps on the NARR charts are in UniversalP a g e | 58

Coordinate Time (UTC). To convert to Mountain Standard Time, subtract 7 hours from UTC (e.g. 18 UTC equates to 11 am MST).

Figure B

. North America Reanalysis valid at 11 am MST, March 26, 2006. Click i mage to enlarge. Click here for a time animation from 11 a m March 25, 2007 to 11 am March 27, 2006. Graphic courtesy Fred Gadomski and the Penn State University Department of Meteorology.

Supporting Meteorological Data: GOES Band

- 12 Data 17 In Figure C, GOES Band

- 12 data shows an upper level weather disturbance located over Colorado and Wyoming at 11 am MST on March 26, 2006. Note the dry air, depicted by the light green color in the 400 to 300 mb layer over southern Wyoming and northern Colorado. The same time convention of UTC applies for the GOES Band

- 12 im ages as in the case for the NARR graphics.

Figure C. 11 am MST, Marc h 26, 2006 GOES Band

- 12 image. Click image to enlarge. Click here for a time animation from 5 pm March 25, 2006 to 4 pm March 26, 2006. Image courtesy of the Data Center at the Space Science and Engineering Center (SSEC) of the University of Wisconsin

- Madison.

17 GOES total column ozone data was unavailable during this SI event.P a g e | 59

Supporting Meteorological Data: Upper Air RAOB ’ s RAOB’s taken at the Denver airport on March 26, 2006 at 5am and 5pm, portray the lowering of the tropopause associated with the passing upper air disturbance and attendant dry air intrusion. Figures D and E show that the tropopause was approximatel y at the 200 mb level at 5 am (1200Z), and lowered to 450 mb at 5 pm (0000Z) 18 . To understand this comparison, note in Figure D the red line veering steeply to the right toward the top of the graphic. This represents the tropopause at 200 mb because air a bove the tropopause will start to warm with height. Figure E depicts the lowering of the tropopause to 450 mb. Note that the warming of air occurs closer to the bottom of the graphic representing a “lowering of the tropopause”. One can determine the lac k of moisture in the air by the increasing distance between the red contour and dashed black contour when comparing both graphics.

Figure D

. Denver, Colorado upper air sounding at 5 am MST, March 26, 2006. Click i mage to e nlarge. Image courtesy Plymouth State University Department of Atmospheric Science & Chemistry.

Figure E

. Denver, Colorado upper air sounding at 5 pm MST, March 26, 2006. Click i mage to e nlarge. Image courtesy Plymouth State University Department of Atmospheric Science & Chemistry.

Additional evidence of an SI having occurred on March 26, 2006 comes from the Global Monitoring Division (GMD) of the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration. The GMD released weekly ozonesondes that provide ozone, relative humidity, and potential temperature data from an instrument package attached to a ballo on. An ozonesonde is like a RAOB but geared specifically toward capturing ozone concentrations. The GMD launched an ozonesonde on March 26, 2006 at 12:56 pm MST from Boulder, Colorado while an SI passed overhead. Figure F depicts the instrument flight d ata in

18 Atmospheric pressure increases with altitude. When one descends in the atmosphere, pressure values increase.P a g e | 60

the vertical. The SI is identified by its signature: a layer of dry air, higher ozone concentrations, and a potential temperature contour that steepens sharply indicating a fast rate of increase.

Figure F

. Boulder, Colorado ozonesonde data from Ma rch 26, 2006. Click i mage to e nlarge.

Supporting Meteorological Data: Isentropic Potential Vorticity, Relative Humidity, and Potential Temperature Cross

- Sections Using the 20

- km RUC 0

- hour analysis in time series, one can view the lifecycle of an SI. Figure G shows a map view where the cross

- section was taken for use in this analysis.

Figure G

. Map view of analysis cross

- section. Click i mage to e nlarge.

Figure H depicts IPV and PT along with a map view of the 500 mb heights and vorticity at 11 am March 26, 2006. The Denver

- Colorado Springs I

- 25 corridor is approximately in the middle of the cross

- section. The animated loop illustrates the 1

- unit IPV surface descending along with theP a g e | 61

steeply sloping potential temperature surfaces, a clear SI sign ature. The right side of Figure H reveals that the passage of the 500mb storm system vorticity core over the Denver

- Colorado Springs I

- 25 corridor corresponds to the 1

- unit IPV surface having reached its lowest altitude.

Figure H

. 11 am March 26, 2006 cr oss - section of IPV and potential temperature (left panel). 500 mb heights (black)/vorticity (blue

- red) (right panel). Click i mage to e nlarge. Click here for a time animation from 6 am to 3 pm, March 26, 2006.

Figure I depicts IPV and RH along the same Denver

- Colorado Springs I

- 25 corridor as in Figure 16. In the area where 1

- unit of IPV descended to its lowest altitude, the air entrained was significantly drier than the air surrounding the intrusion. The combination of descending IPV and low RH air is another aspect supporti ng the presence of an ozone

- rich stratospheric intrusion.

Figure I

. 11 am MST March 26, 2006 cross

- section of IPV and relative humidity (left panel). 500 mb heights (black)/vorticity (blue

- red) (right panel). Click i mage to e nlarge. Click here for a time animation from 6 am to 3 pm, March 26, 2006.P a g e | 62

APPENDIX C

- NARR Explained

Example of the 4

- panel NARR plot of 500 mb heights and vorticity, 700 mb heights and relative humidity, surface pressure and 1000

- 500 mb thickness, and 850 mb heights, temperature, and relative humidity. Explanation on how to interpret this chart follows. Graphic and NARR description courtesy Fred Gadomski and the Penn State University Department of Meteorology.

NARR 500mb Heights and Vorticity Panel

– Top Left
The 500mb Heights and Vorticity Panel can be used to describe the steering flows of the atmosphere. These steering flows are located about 20,000 feet up (about halfway through the atmosphere) and generally direct major weather systems across the country. The black contours are isohypse (lines of constant height), and are contoured every 6 dm (the values on the isohypse are in decameters, i.e. 570 would actually be 5700m). The height of the 500mb level is how far you would have to go up in the atmosphere before the pressure drops to 500mb. Lower heights are usually found to the north while hig her heights are usually found off to the south.
The red and purple shading on the map indicate areas of vorticity in the atmosphere. Vorticity is a measure of rotation throughout the atmosphere. Vorticity can either strengthen or weaken storm systems. Area s of red shading on the panel indicate positive vorticity, while areas ofP a g e | 63

purple shading indicate negative vorticity. The darker the shading is, the stronger the vorticity. Areas of positive vorticity can strengthen areas of low pressure, and are sometimes referred to as “upper

- level disturbances” or “upper

- level energy”. The numbers on the map near areas of vorticity indicate the magnitude of the vorticity.
NARR 700mb Heights and Relative Humidity Panel

– Bottom Left
The 700mb Heights and Relative Humidity Panel is an important panel used by meteorologists. The black contours are isohypse at the 700mb level (roughly 10,000ft), and are contoured every 3dm (the isohypse are in decameters, so 300dm is actually 3000m). The height of the 700mb level is how far y ou would have to go up in the atmosphere before the pressure drops to 700mb. The green and brown shading indicates the amount of relative humidity in the atmosphere at 700mb. (NOTE: This is NOT the relative humidity found at the surface). The green shadin g represents areas with a 700mb RH greater than 70% as indicated by the legend below the panel. Darker green shaded regions represent areas that have a 700mb RH greater than 90%. Light brown areas are regions where 700mb RH is less than 30%, with dark brow n areas less than 10%. White areas on the map indicated regions where the RH is between 30% and 70%.

NARR Surface Pressure and 1000

- 500mb Thickness Panel

– Top Right

The Surface Pressure and 1000

- 500mb Thickness Panel is useful when predicting where storm systems are moving and the type of precipitation that may fall from them. The black lines on this panel are isobars, (lines of constant pressure), and are contoured every four millibars (mb). Some of the isobars are labeled with numbers that usually range from 960mb (a strong low

- pressure system), to 1050mb (a strong high pressure system). Low pressure systems are denoted by a red “L” while high pressure systems are denoted by a blue “H”.
The red and green dashed contours on the map are 1000

- 500mb thickness contours. The 1000

- 500mb thickness is the average depth of a column of air from 1000mb (surface level) to 500mb. The thickness can also be inferred to be the average temperature of a column of air from 1000mb to 500mb. The red dashed thickness contours ar e primary thickness contours (contoured every 30dm, the value on the thickness contours is in decameters), while the green dashed contours are secondary thickness contours (contoured every 6dm). The three primary thickness contours on the panel above are 5 10dm, 540dm, and 570dm. Thickness values lower than 510dm usually represent a dry, arctic air mass found in Canada or along the northern portion of the United States during winter, while thickness values higher than 570dm usually represent a warm and moist tropical air mass from the south. Thickness values can also be very useful in forecasting the different precipitation types from winter storm systems. More information on this can be found here.
850mb Temperature, and Relative Humidity
The 850mb Temperatu re and Relative Humidity panel is used by forecasters to get a general sense of what is going on in the lower

- levels of the atmosphere just above ground level. The 850mb level is about 1500m above ground level, and is a valuable level to use when forecasti ng different the precipitation types associated with major winter storms.
The 850mb relative humidity (like the 700mb relative humidity), is scaled from 0% to 100%, with low humidity values shaded in a dark brown, and high humidity values shaded in a darkP a g e | 64

green. The difference between the relative humidity at 700mb and the relative humidity at 850mb is that the 850mb RH samples the lower

- levels of the atmosphere and can be used to determine if low clouds such as stratus will form. It can also be used to g ive an estimate of the low level moisture in the atmosphere if you know the temperature of the air.
The other contours on the map are isotherms. The yellow contour on the map labeled with a 0 is the 850mb 0°C isotherm. Isotherms in intervals of 5°C are sh own as well, with the

- 10°C isotherm shown as a blue dashed line, the

- 20°C shown as a pink dashed line, the 10°C isotherm shown as a solid orange line, and the 20°C isotherm shown as a solid red line.P a g e | 65

APPENDIX D

- AQS Data

– AMP 350, Raw Data Report for Big Piney, Boulder, South Pass, Daniel, Pinedale, Juel Spring, Yellowstone and Grand Teton National Parks 1

- hour average ozone for June 13

- 16 , 201 2 (Click image to read report).P a g e | 66

APPENDIX E

- AQS Data

– AMP 350 NW , Raw NAAQS Ozone Average Data Report for Big Piney, Boulder, South Pass, Daniel, Pinedale, Juel Spring, Yellowstone and Grand Teton National Parks for June 13

- 16 , 201 2 (Click image to read report).P a g e | 67

APPENDIX F

- AQS Data

– AMP 350, Raw Data Report for Big Piney, Boulder, South Pass, Daniel, Pinedale, Juel Spring, Yellowstone and Grand Teton National Parks all air quality and meteorological parameters for June 13

- 16 , 201 2 (Click image to read report).P a g e | 68

APPENDIX G

- AQS Data

– AMP 350, Raw Data Report for the State of Idaho all air quality and meteorological parameters for June 13

- 16 , 201 2 (Click image to read report).P a g e | 69

APPENDIX H

- 2012 2 nd and 4 th Quarter QA Audit Reports (Click image s to read report s ).