# Presentation: 931407

## Ozone Maximum ModelForecast Version

- Prepared by Bryan Lambeth
- Texas Commission on Environmental Quality
**February 2006**
- Presentation for the National Air Quality Conference
- February 2006 Meeting

**Notes:**
Title slide

## Ozone Maximum Model

- Simple objective technique to estimate magnitude and location of daily ozone maximum concentration for an urban area
- Can be run in diagnostic or forecast mode
- Can be used to optimize monitor siting
- Can be used for screening cases to be examined by dispersion model runs

**Notes:**
Model description

## Basic Concepts

- Background ozone level- level that would occur if there were no local influences - estimated based on levels in areas not downwind- measurements often show a range in background levels
- Peak downwind ozone level- measurements often under-estimate the peak- peaks sometimes occur well outside monitored area
- Local ozone add-on- local peak minus background- critical for local control strategy assessment- important for numerical dispersion model evaluation

**Notes:**
Model concepts

## Measured Ozone Background Levels

**Notes:**
Example of daily measured background levels for the Dallas-Fort Worth area for the summer of 2003.  On individual days, the measured ozone background level can very by as much as 10 or 20 ppb – indicating gradients in the regional background level coming into the area.

## Measured Peak Ozone and Average Background

- Difference is estimate of local add-on

**Notes:**
The difference between the area measured daily maximum 8-hour ozone and the average of the background levels gives a rough approximation of the local add-on.  On most days, the area maximum is probably under-measured by at least a few ppb because the actual peak is often not close enough to the nearest monitor to be fully measured.  On some days the under-measurement may be as much as 5 or 10 ppb or more when the actual peak is well away from the nearest monitor.  The other source of error is possible gradients in the background levels as shown in the previous slide.

## Model Assumptions

- Mobile and area source ozone precursor emissions dominate local ozone production
- May not work as well for areas with large industrial precursor emissions – especially for location estimate
- Peak precursor emissions occur during morning rush hour traffic and greatest pooling of precursor emissions is near sunrise
- Uniform mid-day wind, temperature, and solar radiation field over entire area
- Location estimate may not work as well for complex terrain or coastal environments

**Notes:**
Model assumptions

## Model Input

- Monitored or forecast ozone levels
- Monitored or forecast meteorological data from a representative site
- Wind
- Temperature
- Solar Radiation
- Approximate emissions factor
- Can be calibrated based on past data or estimated based on area precursor emissions totals or area population

**Notes:**
Model input

## Ozone Background Analysis

- _Diagnostic_: use ozone maximums from upwind sites to estimate background level for each day
- Use mid-day wind vector to classify upwind and downwind ozone sites
- Currently using 10 am to 4 pm LDT (6 hours)
- _Forecast_: use today’s estimated ozone regional background levels and forecast transport winds to estimate tomorrow’s ozone background level
- Can also use forecast dispersion model estimate of background levels

**Notes:**
Ozone background analysis

## Local Ozone Peak Calculation

- O3=Upwind+EmFactor*(Tmax-Tb)*SRd/(WSa*0.1+WSp*0.5+1)
- where
- O3 - Local ozone peak prediction
- Upwind - Upwind ozone background level
- EmFactor - Precursor emissions related factor
- Tmax - Maximum temperature in degrees F
- Tb - Base temperature where net ozone production begins (?50 F)
- SRd - Solar radiation total for the day
- WSa - Wind speed near sunrise (using 09-12 UTC forecast mode)
- WSp - Wind speed mid-day (using 15-21 UTC forecast mode)

**Notes:**
Current model formula – still room for improvements.  Constants can be adjusted based on calibration of data in diagnostic mode.

## Ozone Add-On Diagnostic Calibration

**Notes:**
With default emissions factor set to 1

## Ozone Peak Diagnostic Verification

**Notes:**
Results with emissions factor set to 0.3

## Ozone Peak Diagnostic Verification

**Notes:**
Results with emissions factor set to 0.3

## Estimated Ozone Maximum Location

- Use vector sum of mid-day winds to represent net transport of main precursor emissions cloud
- Currently using 10 am to 4 pm LDT
- Calculate latitude and longitude of estimated ozone maximum location based on end of calculated mid-day wind vector referenced to downtown location

## Slide 14

## O3 Max Model Forecast for 2005 August 2

- Based on MOS output from 1200 UTC on 2005 August 1

| O3 Max Model | 08/02/05 Tue |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Forecast | 8-Hour Ozone (ppb) |  |  |  |  | Fcst | Fcst | WSA |  | Wind Vector |  |
| Summary | Upwind |  | Forecast |  |  | Tmp | SRd | 5-8 | 9-14 | Sum 9-14 |  |
|   | Low | High | Add | Low | High | Max | Sum | Avg | Avg | Dir | Dist |
| Dallas-FW DFW NGM | 60 | 70 | 56 | 116 | 126 | 99 | 9.96 | 1.7 | 3.5 | 54 | 16.9 |
| Dallas-FW DFW GFS | 60 | 70 | 42 | 102 | 112 | 103 | 10.10 | 4.0 | 5.8 | 149 | 31.4 |
| Dallas-FW DFW ETA | 60 | 70 | 41 | 101 | 111 | 100 | 9.96 | 3.5 | 5.4 | 161 | 26.7 |
| Dallas-FW C56 Diagnostic | 64 | 67 | 41 | 105 | 108 | 98 | 10.11 | 2.4 | 5.7 | 129 | 24.9 |
| San Antonio SAT NGM | 50 | 60 | 31 | 81 | 91 | 93 | 9.32 | 1.7 | 3.8 | 82 | 22.2 |
| San Antonio SAT GFS | 50 | 60 | 33 | 83 | 93 | 99 | 10.10 | 0.6 | 5.0 | 140 | 29.1 |
| San Antonio SAT ETA | 50 | 60 | 29 | 79 | 89 | 99 | 9.96 | 1.7 | 5.8 | 115 | 23.6 |
| San Antonio C58 Diagnostic | 58 | 62 | 22 | 80 | 84 | 93 | 8.20 | 2.6 | 5.4 | 152 | 23.1 |

- Measured 8-Hour Peaks:  Dallas-FW 115 / San Antonio 84

**Notes:**
Sample case from 2005 August 2

## Forecast Ozone Verification 2005 August 2

**Measured**
**Peak: 115**

- Upwind
- Sites

**GFS**
**112**

**ETA**
**111**

**67**

**67**

**67**

**64**

**65**

**NGM**
**126**

- 8-Hour
- Ozone
- Peaks

**Notes:**
Ozone Max Model forecast 8-hour ozone peaks shown with measured peaks

## Diagnostic Ozone Verification 2005 August 2

**Measured**
**Peak: 115**

- Upwind
- Sites

**Predicted**
**Peak: 108**

**67**

**67**

**67**

**64**

**65**

- 8-Hour
- Ozone
- Peaks

**Notes:**
Ozone Max Model diagnostic 8-hour ozone peaks shown with measured peaks

## Slide 18

**Notes:**
Estimated location of major NOx/VOC plumes shown with 1-hour ozone average and wind vector.  Plume position is at the end of the 1-hour averaging period.  Wind vectors are plotted to scale so that a 10 mile per hour wind is plotted as a vector 10 miles long – in the direction from which the wind was blowing.  The shaded area is a rough approximation of the most dense urban precursor emissions area at 8 am CDT.

## Slide 19

**Notes:**
The shaded 8 am precursor cloud is tracked based on the downtown Dallas estimated plume position

## Slide 20

**Notes:**
The shaded 8 am precursor cloud is tracked based on the downtown Dallas estimated plume position

## Slide 21

**Notes:**
The air that left downtown Dallas around 8 am is estimated to be very close to the measure 1-hour area peak of 133 ppb at 4 pm CDT

## Slide 22

**Notes:**
The air that left downtown Dallas around 8 am is estimated to be very close to the measure 1-hour area peak of 134 ppb at 5 pm CDT

## Slide 23

**Notes:**
The air that left downtown Dallas around 8 am is estimated to be very close to the measure 1-hour area peak of 134 ppb at 6 pm CDT

## Model Comparison

**Measured area max**
**1-hour O3**
**11-12 CDT**

- UH-USA
- IMAQ-MM5

- UH-Texas
- IMAQ-MM5

- BAMS
- MAQSIP-MM5

- NOAA
- CMAQ-NAM

- 2005 August 2
- 11am - Noon CDT

**Notes:**
Comparison of numerical ozone forecast model output for August 2, 2005 at 11 am CDT – before much ozone add-on has formed, but with enough vertical mixing to provide a good indication of deep layer ozone background levels.

## Model Comparison

**Measured area max**
**1-hour O3**
**15-16 CDT**

- UH-USA
- IMAQ-MM5

- UH-Texas
- IMAQ-MM5

- BAMS
- MAQSIP-MM5

- NOAA
- CMAQ-NAM

- 2005 August 2
- 3 - 4 pm CDT

**Notes:**
Comparison of numerical ozone forecast model output for August 2, 2005 at 3 pm CDT.  By this time substantial local ozone add-on is apparent downwind of large urban areas and large industrial sources.

## Model Comparison

**Measured area max**
**1-hour O3**
**17-18 CDT**

- UH-USA
- IMAQ-MM5

- UH-Texas
- IMAQ-MM5

- BAMS
- MAQSIP-MM5

- NOAA
- CMAQ-NAM

- 2005 August 2
- 5 - 6 pm CDT

**Notes:**
One hour of advection of the ozone plumes can be seen when compared with the previous slide.

## O3 Max Model Forecast for 2005 June 2

- Based on MOS output from 0000 UTC on 2005 June 2

| O3 Max Model | 06/02/05 Thu |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Forecast | 8-Hour Ozone (ppb) |  |  |  |  | Fcst | Fcst | WSA |  | Wind Vector |  |
| Summary | Est Upwind |  | Forecast |  |  | Tmp | SRd | 5-8 | 9-14 | Sum 9-14 |  |
|   | Low | High | Add | Low | High | Max | Sum | Avg | Avg | Dir | Dist |
| Houston IAH NGM | 50 | 60 | 49 | 99 | 109 | 95 | 9.88 | 1.7 | 7.7 | 197 | 44.9 |
| Houston IAH GFS | 50 | 60 | 79 | 129 | 139 | 94 | 10.11 | 0.0 | 4.2 | 169 | 24.1 |
| Houston IAH ETA | 50 | 60 | 56 | 106 | 116 | 95 | 9.88 | 1.2 | 6.5 | 211 | 38.8 |
| Houston HOU NGM | 50 | 60 | 72 | 122 | 132 | 92 | 9.88 | 0.6 | 4.2 | 208 | 25.1 |
| Houston HOU GFS | 50 | 60 | 66 | 116 | 126 | 94 | 10.11 | 0.0 | 5.4 | 180 | 30.7 |
| Houston HOU ETA | 50 | 60 | 39 | 89 | 99 | 94 | 9.88 | 2.9 | 9.6 | 213 | 56.2 |

- Measured 8-Hour Peak:  125 ppb

**Notes:**
Example forecast for Houston from June 2, 2005

## BAMS Verification 2005 June 2 - Daily Summary Maps

**BAMS Verification 2005 June 2 - Daily Summary Maps**

**Peak 8-Hour (ppb)**

**Peak 1-Hour (ppb)**

- Area Max:
- Background:
- Add-On:

- Model  93 Measured 125
- Model~60 Measured~70
- Model~33 Measured~55

- Model 111 Measured 147
- Model~65 Measured~78
- Model~56 Measured~69

- Area Max:
- Background:
- Add-On:

- Output from MM5/MAQSIP runs for 0000 UTC on 2005 June 2

**Notes:**
Actual measured background levels were close to 70 ppb on this day.  The BAMS model slightly under-predicted the background level and greatly under-predicted the local add-on.  The Ozone Max Model forecast based on MOS data actually provided a much better forecast of the local ozone add-on, especially based on the HOU MOS data.

## Web Links

- TCEQ Today’s Air Quality Forecast:_[http://www.tceq.state.tx.us/compliance/monitoring/air/monops/forecast_today.html](http://www.tceq.state.tx.us/compliance/monitoring/air/monops/forecast_today.html)_Forecast development and verification is affected by inaccurate TEOM data – both PM10 for dust situations and PM2.5 for winter stagnation events
- TCEQ Air Pollution Events:_[http://www.tceq.state.tx.us/compliance/monitoring/air/monops/sigevents06.html](http://www.tceq.state.tx.us/compliance/monitoring/air/monops/sigevents06.html)_AQI level assigned in these analyses based on TEOM data for dust events may often be over-rated
- TCEQ Air Quality Index Report:_[http://www.tceq.state.tx.us/cgi-bin/compliance/monops/psi_rpt](http://www.tceq.state.tx.us/cgi-bin/compliance/monops/psi_rpt)_AQI shown on this report for high dust events may often be over-rated based on TEOM data

**Notes:**
Web links that show examples of data presentations that are affected by inaccurate measurments.

## This is especially true for forecasters

- When your number is up, make sure it’s unlisted