### Analysis of Ozone Concentrations

Between Select Days During 2005

- 2006

and

Recent Years (2012

- 2014)

Using Comparative Weather Conditions

in the

Memphis Metropolitan Area

### Table of Contents

Overview................................................................................................

........ 1 Methodology............................................................................................. ......3 Water Vapor ...................................................................................................5
Clouds...........................................................................................................5
Wind Direction..................................................................................................7 Wind Speed......................................................................................................8
Other Factors.........

........................................... .. ............................................... 9
Results...........................................................................................................10 The Exceptional Outlier

- June 27 th , 2012 ...................................................................11
Conclusion......................................................................................................12

### Overview: Analysis of Ozone Concentrations Between Select Days During 2005

- 2006 and Recent Years (2012

- 2014) Using Comparative Weather Conditions in the Memphis Metro politan Area

Between the years 2005

- 2007, the 4 permanent ozone monitors in the Memphis m etropolitan area (Edmund Orgill Park

- Millington, TN; Frayser

- Memphis, TN; Marion, AR; and Hernando, MS) met or exceeded the current 2008 8

- hour ozone National Ambient Air Quality Standard ( NAAQS ) of 76 parts per billion (0.076 ppm) on 99 days. In 2011, a 5 th ozone monitor was installed (Shelby Farms is the NCOR site

- Memphis, TN). Even with an extra monitor, there were only a total of 21 days between the years 2012

- 2014 when the 2008 8

- hr ozone NAAQS was exceeded( a reduction of 78.8%). Although the 2015 ozon e season is ongoing at the time that this document i s being written (over 70% complete with the peak season waning) with ozone data that has not yet been certified, there has only been 1 day all year that has exceeded the 2008 8

- hr ozone NAAQS. If the 2015 season concludes with only 1 day above the NAAQS, the 3

- year total of NAAQS exceedance days (days that the Memphis metropolitan area has exceeded the 2008 8

- hr ozone NAAQS) for the Memphis Metropolitan area would be 3, a 97% reduction

.

0 5 10 15 20 25 30 35 40

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 (As of 8/25) 

### Number of Days that Exceeded the 2008 O3 NAAQS Memphis Metro Area

Days the 2008 O3 NAAQSExceededMemphis Metro AreaDaysExceeding 76 ppb-2008 O3

Year

Page | 1In addition to the massive reduction in the number of exceedance days, the ozone concentration levels have also significantly decreased. The ozone design values (the three

- year average of the 4 th highest daily 8

- hour ozone maximum per year, which determin es whether a monitor is violating the NAAQS) during the years 2005 and 2006 were 86 and 87 parts per billion (ppb), respectively. The ozone design values in 2013 and 2014 were 78 and 73 ppb, respectively ( with a design value in late August

- 2015 of 67 ppb). The design value graph can be found as Figure 1 in the Shelby/Crittenden/DeSoto Counties 8

- Hour Ozone Design Value of the “SCR R AMP

- 2015” For the 2008 Eight

- Hour Ozone National Ambient Air Quality Standard. After further research, the disparity between the start of the study (2005) and the end of the study (2014) continues to be significant when comparing the top ten daily maximum 8

- hr ozone concentrations for each year (data table can be found in the appendix with the graph shown below). Note that the 10 th

- highest ozone concentrations from both 2005 and 2006 were still greater than the strongest ozone concentrations in both 2013 and 2014.

The incredible difference be tween the number of ozone exceedances between the first few years of the comparative study and the last few years (The study mainly concentrated on the years 2005

- 2006 and 2012

- 2014) as well as the significant decrease in ozone concentrations during the period led to the hypothesis that weather alone could not be the driving factor in thes e vast ozone reductions during this 10

- year period. It was believed that for the most part, a known lower emissions inventory played a larger role in ozone reduction than weather conditions during the period of 2005

- 2014 (and is continuing to occur from th e initial data t hat is being compiled for 2015), but needed further study. 60 65 70 75 80 85 90 95 100 105 110

1 2 3 4 5 6 7 8 9 10 2005
2006
2013
2014 Top Ten Daily Max 8

- HR Ozone Conc.

- Memphis Metro 2005

- 06 & 2013

- 14Ozone Concentration(ppb)

Rank

Page | 2Methodology In order to test the hypothesis, the 8

- highest ozone concentrations (8

- hour daily maximum ozone concentrations from the Memphis Metropolitan Area ozone monitors) were ch osen from 2005 and 2006 (4

- highest concentrations from each year) and compared to days with similar weather conditions during the years 2012

- 2014. Each of these 8 days would have been labeled a “Code Red” for ozone under the current 2008 8

- hr ozone NAAQS. Once an acceptable number of comparative days were compiled and analyzed, ozone values from each of the selected days could then be compared to determine if there might be another source of strong influence to the ozone development (or lack thereof) , such as emission inventory . Each of the 8 days from 2005 and 2006 were compared to 9

- 15 days from 2012

- 2014 with acceptably equivalent weather observations from the same surface station (Memphis International Airport) . The acceptability criteria will be explain ed later in the Methodology section

. For the last several years, the Shelby County Health Department has been collecting weather conditions at the Memphis International Airport (KMEM) in addition to the daily maximum 8

- hour ozone concentrations for each mo nitor in the metropolitan area. The weather parameters were initially collected in order to improve forecasting techniques, but have since proven to be useful for other means, as well. The example below shows the complete set of collected weather parameter s

.

A B C D E F G H I J K L M N O P Q R S T U V
6/27/2013 61 59 67 58 57 67 97 76 74 21 51 111 12

- 7p SCT

- W6 (TS/RA/SQ later) 9.88F 5 C 98/74 46 110

This example has been compacted in order to fit within the document. The headers were also removed due to space restrictions. The numbers under letters B

- F indicate the 8

- hr maximum ozone concentrations (in parts per billion) for the day and are color coded to the AQI with the monitor with the maximum concentration in the area for the day in bold type

. A=Date B=Edmund Orgill Park ozone monitor

- Millington, TN C=Frayser ozone monitor

- Memphis, TN D=Shelby Farms ozone monitor

- Memphis, TN E=Marion, AR ozone monitor F=Hernando, MS ozone monitor
G=Maximum 8

- hr ozone concentration (ppb) for the Memphis area on the given day

Page | 3H=Maximum daily temperature

- °F (all weather data observed at Memphis International Airport, unless otherwise stated) I=Dew Point (°F) at the time of the max temperature (at times it must be the best meteorological estimate, as max temperatures often are recorded between hourly observations) J=Minimum Daily Temperature (°F) K=Dew Point Depression at the time of the max temp (difference b etween Max Temp and Dew Point) L=Relative Humidity at the time of the max temp (%)
M=Heat Index

- °F at the time of the max temp (only recorded if 95 ° or higher) N=Hours of maximum ozone concentration at the high monitor (The 12:00 hour in 12

- 7 reflects the ozone observed from 11 am

- 12pm)
O=L abeled WX (weather) comments, but lists cloud cover, wind speed, wind direction, and any other pertinent information at the time of the max temp (in this case a thunderstorm, rain, and squall line pushed through the area later after the high temperature was recorded) P=Barometric Sea Level Pressure (SLP) equivalent at the airport during the max temp (in inches) as well as the pressure trend (in this case, the SLP was 29.88 inches and falling) Q=Daily Rainfall amount using GFS MOS categories (0=No rain or trace, 1=0.01

- 0.09 inches, 2=0.10

- 0.24 inches, 3=0.25

- 0.49 inches, 4=0.50

- 0.99 inches, 5=1.00

- 1.99 inches, 6=2.00 inches or more) R=Shows if a front or trough passed through the area on the given day and if so, the type (C= cold front, W=warm front, S=stationary front, T=trough, and Trop=tropical system) S=Shows if a front or trough passed through the area on the previous day (if there is no passage, the space will be left blank) T=West Memphis, AR airport weather observation station (WMEM) Max Temp/Dew Point U=WMEM Relative Humidity (%) at the time of the WMEM max temp V=WMEM Heat Index (°F) at the time of the WMEM max temp

Although this surface data is extensive, only six weather parameters were used in the comparison between the selected days. They were Max Temp (H); Dew Point Depression (K); Relative Humidity (L); Cloud Cover (which was expanded to include cloud heights in the study); Wind

Page | 4Direction; and Wind Speed (clouds, wind direction, and wind speed al l fall within the O column). The Max Temp, Dew Point Depression, and Relative Humidity parameters were compared during the hour when the maximum temperature was recorded. The Cloud Cover (as well as C loud H eight ), Wind Direction, and Wind Speed parameters were averaged over an 8

- hour period (11am

- 6pm CDT ) using the National Climatic Data Center database and then compared for the selected days. The Cloud Cover, Cloud Height, and Wind Direction parameters were each given a weighted value in order to quantify the comparison. The points given to each of these variables is called the Weather Relevance Score (WRS) and is explained in detail below.

Water Vapor As exact temperature comparisons were not as much of a concern as the Dew Point Depression or Relative Humidity, a 3

- degree cushion was allowed between the high historical day (2005

- 2006) and each of the days between 2012

- 2014. If the temperature difference exceeded the 3

- degree cushion, a 0.25 point per degree was given to the day with the higher tempera ture. For example, if day 1 recorded a max temp of 100 degrees and day 2 recorded a max temp of 94 degrees, day 1 would be given a temperature score of 0.75. This would then be added to the other variable s for a final WRS score. After many years of study, it has been determined that water vapor plays a major role in the development of ozone in the Memphis area. As such, the water vapor score was divided into Dew Point Depression (the difference between tem perature and dew point) and Relative Humidity. Although in many instances, the two parameters coincide in relation to the WRS, it was not always the case. Both variables were important to the outcome of the WRS. For each degree of difference in the Dew Poi nt Depression variable, a 0.25 point was given to the day with the higher Dew Point Depression. A higher Dew Point depression reveals drier air (more conducive to ozone development). Similarly, Relative Humidity also shows water vapor in the air relative t o the temperature. For each percentage point of difference, a 0.25 point was given to the day with the lower relative humidity percentage. Both water vapor variable scores were added to the WRS. The tables used to score the dew point depression, relative hu midity, and maximum temperature can be found in A ttachment II

. Clouds After compiling the temperature and water vapor scores (all were scored during the hour of maximum temperature), an 8

- hour window was used to compare cloud cover (including cloud height) , wind direction, and wind speed. These variables were then averaged, scored, and added to a final WRS score in order to determine if the weather conditions were comparable. If the weather scores were deemed comparable, ozone concentrations could then be s tudied. The 8

- hour window used surface data from Memphis International Airport (gathered from the National

Page | 5Climatic Data Center) , the official weather station for Memphis, and averaged observations from 11am

- 6pm CDT. Cloud clover was broken into 5 main categories with 4 sub

- categories to fill in the gaps. The 5 main cloud categories (with initials) are Clear (CLR), Few (FEW), Scattered (SCT), Broken (BKN), and Overcast (OVC). Each of these categories used show a percen tage of cloud cover (estimated for this study) and assigned a value.
CLR=0% cloud cover

- fair skies

- 0 points
FEW=10% cloud cover

- mostly sunny skies

- 1 point
SCT=50% cloud cover

- partly cloudy skies

- 5 points
BKN=80% cloud cover

- mostly cloudy skies

- 8 points
OVC =100% cloud cover

- overcast skies

- 10 points As the cloud cover can often fall between these categories and cloud heights can also reflect thickness (high cirrus clouds are generally not as dense and allow more radiation to reach the Earth’s surface), sub

- ca tegories were used in order to give the score a little more accuracy. The sub

- categories are High Overcast (OVC skies over 12,000 feet, but generally between 18,000

- 25,000 feet), High Broken (over 12,000 feet), High Scattered (over 12,000 feet), and a sub

category called Few

- High Scattered, which was only used when the average score was too high for few, but not enough to fall with the high scattered sub

- category. There were also occasions where an extra point would be added when the cloud heights had mixed cloud

- types, such as broken at 25,000 feet and scattered at 10,000 feet. The cloud coverage warranted a higher score in those circumstances. The ranges for the cloud categories and sub

- categories are as such:
Clear=0.0

- 0.5 points
Few=0.51

- 1.74 points
Few

- High Scattered=1.75

- 2.24 points High Scattered=2.25

- 4.24 points (High SCT given a value of 3.5 for a 1

- hour observation)
Scattered=4.25

- 5.00 points High Broken=5.01

- 6.49 points (High BKN given a value of 5 for a 1

- hour observation)
Broken=6.5

- 8.00 points

H igh Overcast=8.01

- 8.99 points (High OVC given a value of 8 for a 1

- hour observation)

Page | 6Overcast=9

- 10 points

Once the 8

- hour cloud cover total is averaged for each day, it is then given a category or subcategory. Each category will then be compared to one an other and given a score, which is then added to the WRS. If the categories match, no score is added. 1 category difference (i.e

. - CLR to FEW) is equal to 1 point on the WRS. 2 or more category differences will add 1.5 points for each additional category cha nge, as cloud cover can affect solar radiation and play a major role in ozone development. For example, if day 1 averages clear skies and day 2 averages broken skies, a difference in 3 categories, a 4

- point score will be given to day 1 (1+1.5+1.5=4). If th e sub

categories High SCT, High BKN, and High OVC are involved, the category score would be halved. For example, if day 1 averages a High SCT and day 2 averages a SCT, then day 1 would be given 0.5 points to add to the WRS, as high SCT is considered to hav e less cloud cover. If day 1 averaged a high SCT and day 2 averaged BKN skies, this would be considered a difference of one and a half categories and day one would be given 1.75 points for the WRS score (1 category would be a full point and the half catego ry would split the difference of a second category difference 1.5/2=.75 for a total of 1.75 WRS points). The FEW

- High SCT category splits a category and a sub

- category and then only adds a total of 0 .25 WRS points. For example, if day 1 averages a FEW

- High SCT and day 2 averages SCT conditions, then 0.75 WRS points would be given to day 1 for a half category plus the 0.25 point bonus. The tables that were used for scoring and averaging the cloud cover can be found in A ttachment II

.

Wind Direction The wind direction variable can determine not only which monitor will most likely be affected , but can also play a role in the concentration levels. Although calm winds are usually associated with wind speed, if the parcel of air is remaining in one place during favorable hours (late morning to early evening), this can help ozone levels increase rapidly and therefore would be given added value when quantifying this parameter (will explain in detail below). Variable winds tend to be light in nature and can a lso be associated with increasing ozone concentrations. If there are several hours of light and variable winds, ozone levels can increase as the parcel tends to remain over an area for an extended period of time. Variable winds have also been given added v alue, although not as great as a calm wind observation.

In general and depending on wind speed, a forecaster can determine which monitor will see higher levels of ozone with an accurate wind direction forecast. Southeasterly winds will

Page | 7generally increase ozone concentrations at the Frayser and Marion monitors . Southerly winds can affect the Marion, Frayser, Edmund Orgill Park, and Shelby Farms monitors. Northerly and northwesterly winds can affect Hernando monitor. Easterly winds can affect the Marion, Fr ayser, and Shelby Farms monitors. Westerly winds can affect the Shelby Farms monitor. The only directional condition that does not affect the area ozone monitors is Northeasterly. This is because there are no ozone monitors southwest of the Memphis area (p ossibly due to sparse population in the area).

The wind direction variable had to be quantified in a way that increased during conditions when ozone conditions were more favorable and decreased due to a known factor that was presentwhen ozone levels were lower. On the comparative days, each hourly wind direction observation at Memphis International Airport during the 11am

- 6pm CDT period was given a value. All of the directional winds (N, S, E, W, NW, SW, SE, ESE, SSE, SSW WSW, WNW, and NNW) were given the value of 1 with the exception of NE and its variations (NNE and ENE). Because the ozone values are generally lower on days with a prevalent northeasterly wind, NE was given the value of 0.5 0 . NNE and ENE were each given the value of 0.75. Since calm winds are associated with increased levels of ozone, a calm observation was given the value of 1.50. Light and variable winds are also associated with higher levels of ozone, but not quite as high as calm winds, so a variable observation was given the value of 1 .25. The 8

- hour period was totaled and averaged. If one day averaged more than 0.125 than another, it would be given a WRS value of 0.25 to add to the total score. If one day averaged more than 0.375 in comparison to another, it would be given a value of 0 .50 to add to the WRS score. For example, day 1 recorded an 8

- hour (11a

- 6p) average of 1.22, while day 2 averaged a score of 1, then day 1 would be given a point value of 0.25 to add to the WRS score. If neither day has an advantage of over 0.125, then no score is given for the wind direction variable for that specific comparison of days. The tables that were used for scoring and averaging the wind direction can be found in A ttachment II

.

Wind Speed The wind speed variable is very important in the process of ozone development. Winds at the surface and aloft not only help to transport ozone and its components, but create atmospheric mixing, which causes dilution reducing the amount of ozone (as well as many other pollutants). Calm to light winds will not create much atmospheric mixing, which make conditions favorable for rapid ozone development. Although winds above the surface are critical to the development of ozone, Memphis does not have a definitive way to measure them, as there is no regular

soun ding in the area (weather balloon). The nearest locations that have sounding measurements are Little Rock, AR; Jackson, MS; and Nashville, TN. None will be used in this comparison, due to distance. We will use the surface winds as a surrogate, since the ob servation station is relative

Page | 8to the area and the ozone monitors. For instance, calm winds are usually the product of strong high pressure at the surface and aloft. Several hours of calm winds during the hours when ozone is most likely to develop are indic ative of strong ridging. Days that have higher wind speed averages can still experience ridging, but may also have a pressure gradient building into the area. Short wave troughs can also produce higher wind speeds in areas that are under high pressure. I f an inversion breaks late in the afternoon, wind speeds can increase after being fairly dormant for much of the day.

For this comparison, the 8

- hour (11a

- 6p CDT ) wind speed averages were used for the days that were being equated. Gusts were incorporated when determining the average by calculating the difference in the sustained speed and the gust speed and then dividing by 2, since the full gust would not be an accurate indication of the hourly wind speed. The gust would show that there was an occasional increase and therefore stronger mixing rates, so it was important to incorporate this factor. The total difference in gust and sustained speeds for the 8

- hour average was calculated, divided by two, and added to the total of sustain ed speed for a new total and then divided by 8 for the average wind speed for the period. For example, if 3 of the hours recorded sustained speeds of 8 mph for each hour with gusts of 12, 14, and 16 mph, respectively, the total difference between the susta ined winds and the gusts would be 18 mph (12

- 8=4, 14

- 8=6, 16

- 8=8, thus 4+6+8=18). The number 18 would then be cut in half to 9, which would be added to the total of the 8

- hour sustained speed s and then divided by 8 for the average of the period.

The days with lighter wind speed averages were rewarded with WRS points . Rounding was used when the days were compared. A value of 0.25 was given to the day for each difference in mph for the 8

- hour average. For example, day 1 averaged 5 mph and day 2 averaged 10 m ph. The difference of 5 miles per hour would give day 1 a score of 1.25 to use for the WRS. The tables that were used for scoring and averaging the wind speed can be found in Attachment II

.

Other Factors Upper

- air factors such a pressure, wind speed, and w ind directions are very important, but cannot be quantified due to a lack of localized measurements. However, archived upper air charts are included in the appendix to give a synoptic look at the comparative days. These charts are provided to show how the upper air patterns were structured synoptically on the given days.

I t should be noted that the 8 days from 2005 and 2006 were compared with days from 2012

- 2014 during similar periods. A 3

- week time frame was imposed for the comparison in order to accuratel y compare the dates with similar sun angles, solar radiation, and length of day. For

Page | 9example, to accurately compare the 6/23/2005 date, the window of acceptable comparative dates would have to come from a period in 2012

- 2014 from 6/2 to 7/14, 21 days befor e or after the historic date. The 2005

- 2006 dates as well as the 2012

- 2014 dates with the comparative scoring tables , upper air and surface charts, and hourly weather observations from the National Climatic Data Center can be found in the appendix.
Reviewi ng the comparative dates to include in the study was a bit difficult. There were many examples of both acceptable and unacceptable weather conditions, but the report needed to be revised to a reasonable amount of qualified dates to be both produced and rev iewed. Determining the threshold for acceptable weather conditions was difficult, but there appeared to be moderate differences past the

- 2.5 mark for the 2012

- 2014 dates. The positive 2.5 +WRS scores showed differences as well, but were chosen to rema in included in the study. The strong positive WRS

scores translated to weather conditions that were strongly more favorable than the 2005 and 2006 dates, but still showed mu ch lower ozone concentrations. Most of t he days with strong negative number ed days were left out, as they showed low ozone . This would be expectedwith weather conditions that were not conducive to ozone development . A score of zero was a match for the

we ather conditions. Scores of 0.0 to 2.50 (or

- 2.50) were consider ed a good match. Scores of 2.75 to 3.50 (

- 2.75

- 3.50) were considered fair. A WRS score above (or below) the 3.50 (

- 3.50) mark were not considered as a good or fair match . As stated above however, many of the strongly positive scores from 2012

- 2014 were inc luded because the conditions showed that they were much more favorable toward ozone development, but showed lower concentrations than the 2005

- 2006 dates.

Results Once the acceptable comparative dates were compiled, the scores were then matched against

ea ch historic (2005

- 2006) date within the comparative study. Since the threshold for a good Weather Relevance Score (WRS) was 2.5 (or

- 2.5), it was determined that each WRS point would be calculated to equal 4 parts per billion (ppb) of ozone per 1 WRS point . This would translate to up to 10 ppb within the good range for weather relevance acceptability and 14 ppb for the fair range of acceptability. T he WRS for each recent date (2012

- 2014)of comparison was multiplied by 4 with the sum then added (or subtracted ) to the ozone concentration of the individual historic date of comparison (See the associated tables and graphs in A ttachment II ). The results show that for the most part, a significant increase in the 8

- hour ozone concentrations would have occurred had t he ambient air conditions of 2005 and 2006 been matched against the actual ozone concentrations and weather conditions from the comparative dates in 2012

- 2014. The 2012

- 2014 dates with the highest levels of ozone experienced weather conditions that were far more conducive to very high ozone levels, but were still found to have lower concentrations than the historic dates f rom 2005 and 2006. This strongly suggests that weather did not play a

Page | 10role in the decreased ozone concentrations over the last 8

- 10 years (See the R esults tables and graphs in A ttachment II ).

It is important to note that this study and the results are not intended to be interpreted as exact projections, but should be used to illustrate the concept that the weather conditions have not been the major factor in the reduction of the number of days that ozone has exceeded the NAAQS as well as the reduction in o verall ozone concentrations in the Memphis metropolitan area. The study and its associated tables and graphs were produced to assist the reader in visualizing the vast difference in ozone exceedance days and concentration levels in the last 8

- 10 years.

Th e Exceptional Outlier

- June 27 th , 2012 One date from the most recent few years was left out of the study, as the weather conditions were so exceptional, it was determined that it might skew the rest of the comparison. Therefore, it was compared to the historic dates on its own. On June 27 th , 2012, the Frayser monitor recorded an 8

- hour ozone maximum of 124 ppb

- Code Purple (also on that date, Shelby Farms

- 98 ppb

- Code Red; Marion

- 88 ppb

- Code Orange; Orgill

- 80 ppb

- Code Orange). The weather conditions on th is day were incomparable with any other date in recent memory. The max temperature for the day

was 98 degrees F with a dew point of 47 degrees, a 51

- point dew point depression! The relative humidity at the time of the max temperature was 18%, which can be likened to near
- desert conditions. Every sky observation at KMEM during the 8

- hour period that was being used in this study to determine average cloud cover (11am

- 6pm) was clear. The 8

- hour average wind speed was just over 2 MPH with the wind direction sco re averaging just between the calm and variable categories.

These conditions were due in part to an incredibly strong upper

- air ridge that was over the middle portion of the country including the Memphis metropolitan area. A very strong surface high pres sure system over the Southeast U.S. complimented the conditions on 6/27/2012. On the previous day as the ridge was over the eastern Great Plains, Houston recorded a Code Purple with cities east of Memphis recording Code Red and Code Purple conditions on 6/ 28/2012. Very strong high pressure continued to affect the weather and ozone in the Memphis metropolitan area for the next few days with several exceedance days , but nothing close to the conditions that were recorded on the 27 th . After using HYSPLIT to det ermine if transport was a factor from the Houston area or other cities west of Memphis, it was proven that there was no transport from those areas.

Page | 11Using the same WRS scoring method to attempt to compare the weather conditions on 6/27/2012 to the historic high ozone days of 2005 and 2006, it was found that the conditions on the 27 th were profoundly stronger than any of the historic dates. The 2005 and 2006 Weather Relevance Scores when compared to the weather conditions on 6/27/2012 were between

- 8.25 and

- 18.50! See the chart and the graph to see how the WRS scores affected projected ozone levels.

Conclusion Before the study, it was suspected that factors other than weather were the major force in the reduction of days and concentration levels of ozone. Weather patterns had not appeared to change drastically and yet Memphis was experiencing incredible reductio ns in less than a decade. Although the 2015 ozone season is waning, but not complete, the monitored data has been consistent with a vast reduction in ozone exceedances and concentration levels from the 2013 and 2014 seasons. The comparison between the 2005

- 2006 data and the 2012

- 2014 data show similar weather comparisons (with several days in the recent period showing weather conditions more conducive to favorable ozone), the 2005

- 2006 seasons still showed much higher levels of ozone . After incorporating th e ozone scoring (4 ppb per 1 WRS point), the 2005

- 2006 dates projected an average increase of more than 51% compared to the actual ozone data of the comparative dates of 2012

- 2014. This strongly suggests that weather was not the driving factor in the reduc tion of ozone exceedance days and overall concentration levels. Other factors, such as significantly reduced emissions in the Memphis metropolitan area (see emissions portion for further details) may have played an increased role in the overall air quality improvement for the Memphis metropolitan area.

Page | 12