# Presentation: 844373

## Atlanta Ozone andPM2.5 Forecasting

**Atlanta Ozone and****PM2.5 Forecasting**

**Notes:**
Clean day-March 6, 2001

**Notes:**
Bad O3 day-Sept 11, 2002. Sounding for this day follows. 14 sites statewide had O3 violations, PM2.5 hourly reading was 40.2 microg/m3 at South Dekalb. Metro had 8 ozone violations, 13 statewide, including Fort Mountain.  McDonough had 113 hourly O3 avg.

## Forecasting:

- Began forecasting ozone for Metro Area in 1996.
- Began forecasting PM2.5 for Metro Area in 2003.

**Notes:**
Also forecasted for the Summer Olympics in 1996.

## Forecasting Program

- Team consists of meteorologists and air quality modelers from Georgia EPD and Georgia Tech.
- Forecasting Tools:
-  a. Multiple Linear Regression Model, Decision-Tree, Close Neighbor Models
-  b. UAM (3D clear-sky)
-  c. Meteorological and Chemical Data
-  d. NWS Synoptic Models (GFS,ETA....)
- Methodology:
-   Consensus Component, Submit forecast at 1330 LST.
- (Discussion with NC and SC)

**Notes:**
Ours is not fixed, every day we select from history what is close to tomorrow predictions. Increase size of selector. Based on color not number. Meteorological and Chemical data is real-time observations. European and Canadian models are also important. Regression models use independent variables (meteorological and chemical) to predict the value of a dependent variable. This model uses predictor variables (WSP, WDR, Tmax,Tmin, Sky, Pres, Day of week, Previous day maximum 8 hr average ozone, calendar date,  max daily Td, min daily Td. Decision Tree Model combines historical data with chemical and weather predictions. It uses 2448 historical records, where each record corresponds to an ozone-season day during the period 1987-2002. The Close Neighbor Model uses data from the NGM forecast model to find days in the past that are most meteorologically similar to the forecasted next day. The UAM is a 3Dphotchemical-transport grid model. The Atlanta UAM modeling domain is 40 x 40 horizontal grid of 4 x 4 –km cells with 5 vertical layers. In most cases UAM is executed as a diagnostic tool to simualte a past event. However, it is a prediction tool, so input parameters to the UAM-FM (Forecast Mode) are based on meteorological and chemical predictions. Biogenic emissions are computed daily based on ambient temperature and solar radiation. Anthropogenic emissions are assumed to be the same every day except for the variation between weekdays and weekends. It provides better spatial distribution of ozone concentrations than regression models. 

-  ATLANTA FORECASTING TEAM
-     O3 PREDICTIONS
- Successful predictions (1999-2003)
- Year    Binary           AQI #Viol
- ----------------------------------------
- 1999     83.7%         53.6%  69
- 2000     81.7%         58.2%  46
- 2001     86.9%         63.4%  20
- 2002     84.3%         66.0%  37
- 2003     93.3%         67.8%  13

**Notes:**
Binary=if orange or higher vs below orange. Ozone event to non-ozone event. Only 11 violations in 2003.

- PM2.5 PREDICTIONS
- Successful predictions (Oct 2003 - Jan 2004)
- Year      AQI Category
- -----------------------
- 2003         76.1%
- 2004          ??          (1 Viol)

## Metro Ozone Network

**Notes:**
We forecast for 4030 sq miles (13 county non-attainment area) for metro area. I’ll be talking about an ozone and a PM2.5 episode that occurred at Douglasville and Yorkville (indicated by blue line). Douglasville had the elevated ozone reading and Yorkville had the elevated PM2.5 reading.

## GA PM2.5 Network

**Notes:**
We forecast 4000 square miles for Metro area. 2 arrows denote location of elevated PM2.5 readings (Yorkville and Macon).

## PM2.5 and O3 Episode(8/19/03)

**Notes:**
34.4 micg/m3 at Yorkville (24 hr avg for 2300 LCL on Aug19). 8 hr ozone was 85 ppbv at Douglasville. I will first talk about O3 first, then PM2.5.

## Recirc at Douglasville(NW to SE flow)

**Notes:**
I will talk about ozone first, then PM.5. Ozone buildup plus recirculation at Douglasville. Winds swung from NW to SE. 

**Notes:**
Sometimes trajectories don’t tell the complete story, which is why I use synoptic charts first to check air mass. Using vertical motion (Kinematic method). Streamline analysis better to use here because of stationary front. Trajectory is verifying reciculation over Douglasville. Here is an example where sometimes the trajectory can help tell the story.

## PA1-LR 500,1000m WDR

**Notes:**
Sodar really does a nice job of showing recirculation episodes looking at 500m and 1000m winds. Note shift in WDR from WNW to SSE on 8/19. The SSE shift is coincident with Douglasville O3 increase on 8/19. So this was not just a surface feature. Spike on 18th (500m winds) is due to ambient noise (N) at surface.

## FFC Sounding 8/19/03

**Notes:**
Mixing height is important for PM2.5. Good mid-level drying with surface inversion and 700mb inversion. Split flow and strong surface inversion with minor instability, fairly steep lapse.We could still have an ozone violation, if afternoon convection holds off late enough in afternoon.

**Notes:**
Potential temp constant with height indicates unstable layer (good mixing), theta changing with height indicates top of mixed layer(very stable layer). Gradual change of theta with height indicates slow evolution of the mixing height on 8/19. Here you can see potential temperature slowly changing with height throughout the day. 

**Notes:**
The Synoptic Situation at the surface showed a quasi-stationary diffuse occluded front across Ga (with weak Atlantic flow over NE Ga, but not strong, since High is not positioned far enough offshore).

**Notes:**
This Synoptic Upper Air chart for 19 August shows a broad strong upper level ridge building over eastern US. This chart is based on 500mb rawinsonde upper air data. Close to 6000m geopotential height ridge is very strong for the SE. This verifies that we have strong High pressure over the SE with fairly stable conditions over north Ga.

**Notes:**
More Synoptic Upper Air: 500mb forecast heights and Absolute Vorticity Chart for 20 August. Note Weak PVA to west moving along trough axis which punches up or intensifies ridge. This was the forecasted product which shows a wave upstream.

## Yorkville and Macon PM2.5  8/19/03-8/20/03

**Notes:**
Yorkville PM2.5 levels remained high on the 20th, whereas Macon PM2.5 levels dropped off on the 19th due to afternoon convection.  It was also interesting to look at Macon PM2.5 and see what was going on just south of Metro. Yorkville is in Metro area, and although Macon is not, Macon still had elevated PM2.5 values. Note we have 2 different days here for PM2.5 (19th and 20th). Note the gradual buildup as WSP stays less than 5 m/s at both sites. Note PM2.5 bounced back above 20 microg/m3 after isolated convection at Macon late on the 19th. Yorkville had a 44 microg/m3 (24 hr avg) on the 20th which is considered unhealthy (orange) for sensitive groups.

**Notes:**
 METEOROLOGICAL SUMMARY of 19th and 20th at FFC (Half way between Yorkville and Macon). Here is a nice product that summarizes surface and upper air from NOAA ARL. NW shift to SE shift on 19 August showing recirculation (circled area). Kink in 500 mb heights indicative of weak diffuse stationary front. We had an increase in RH and a decrease in WSP on the 20th, which is why PM2.5 stayed high at Yorkville. Light WSP during the afternoon on August 19. Neutral 500mb heights on 20 August. This meteogram gives a nice overall summary which depicts stationary front over central Ga. High 850RH in conjunction with low wind speed late in day on the 20th gave high PM2.5 at Yorkville.

## Forecast for 8/19/03

- Upper level ridge maintains grip over SE showing only minor weakness in the extended period. Expect diurnal convection and Cu field to continue over north GA with late afternoon isolated convection mostly central and south GA. Light SW flow should keep _PM2.5 levels in high moderate range_, _while O3 for Metro could sneak into low orange for Tuesday_ with some residual buildup over next 24 hrs. Could be advection fog around tomorrow AM with increase in warm air advection below 850mb.

**Notes:**
Typical forecast discussion – had PM2.5 and O3 violation. I plan to analyze this particular case study. I’ll run you quickly through an interesting case study where the PM2.5 and O3 both increased in concert.

**Notes:**
This is what makes it so tough to forecast PM2.5. This visible satellite imagery shows afternoon convection breaking out along a stationary front. Although afternoon convection around, Macon and Yorkville both increased in PM2.5 on 19 August (17Z).  Afternoon convection in Macon (green arrow) bumped PM2.5 down a little but did rebound somewhat, while Yorkville PM2.5 (denoted by red arrow) stayed high through the 20th  and had a violation, indicating that PM2.5 problem is not really spatially homogeneous in this particular synoptic situation.

## Conclusion

- Ozone increase at Douglasville was primarily due to recirculation.
- Concurrent PM2.5 increase at Yorkville was due to multiple inversions, slow evolution of mixing height, and light boundary layer winds.
- Macon PM2.5 levels were affected by front and afternoon convection.
- Broad upper level ridge was dominant synoptic feature for this O3 and PM2.5 episode.
- .

**Notes:**
Metro maybe has 20 % recirculation episodes a year. The tough ones to forecast are when both the PM2.5 and the O3 are both high. Different things are happening in the boundary layer which could be more conducive to higher PM2.5 levels than for O3. This episode was interesting because here we had a day where O3 ramped up due to recirculation, while PM2.5 gradually climbed due to multiple surface inversions and the slow evolution of the mixing height. The dominant synoptic feature to give the slow evolution of the mixing height was a broad upper level ridge (almost 6000m). Ozone episode seemed more clear-cut than PM2.5 episode. PM2.5 behavior at Macon was different than at Yorkville due to a weak stationary front positioned over central Ga.

## Future:

- LIDAR and SODAR will be useful in probing evolution of mixing height and capturing smaller-scale recirculation episodes.
-  Understanding strength of nocturnal inversion and early morning cap is critical concerning O3 and PM2.5 interplay.

##           The End