Quick Links

• Meteorological Data
• Ozone Data
• NO₂ Data
• Modeling Guidance
• Modeling Resources

The District no longer accepts analyses performed using the Industrial Source Complex –
Short-Term (ISCST3) model.

All meteorological data have been processed with AERMET, Version 06341.

Meteorological Data (Only for use in the AERMOD model)

The District has meteorological data sets to be used for modeling sources in the San Joaquin Valley. Please download the latest data sets. Use the most recent five years of meteorological data. Model all five years. Use all the data available for a site if less than five years of data are available. For a cancer or a chronic non-cancer risk assessment, the average cancer risk of all years modeled should be used. For an analysis of compliance with ambient air quality annual standards, each year's data set should be modeled separately to obtain a maximum annual average concentration for each year. Then, the maximum annual average concentration predicted for the five years modeled will be compared to annual average standard.

Meteorological data are available from two sources: 1) the National Climatological Data Center (NCDC) and 2) the MM5 Numerical Model. NCDC data were collected at major airports in the Valley. These data can be used for health risk assessments and ambient air quality analyses. The data derived from the MM5 numerical model are for sites where there are no airports. MM5- derived data can be used for health risk assessments. They cannot be used for ambient air quality analyses.

All meteorological data sets have been compiled from one-minute data using AERMINUTE with a wind speed threshold of 0.50 m/s. AERMET adjusted Friction Velocity (u*). In AERMOD, the non-default option of “Adjusted Friction Velocity (u*) in AERMET (ADJ_U*)” must be used. No low wind options can be used.

Both U-Star adjusted and non-U-Star adjusted meteorological data are available. Select the appropriate folder from our FTP server. Clicking on the link below will direct you to the files.

Meteorological Data FTP

Air Quality Monitoring Sites

Ozone Data (Only for use in the AERMOD model)**

Select the appropriate county folder from our FTP server. Clicking on the link below will direct you to the files.

Ozone Hourly Data

Ozone 5 Year Max Data

Ozone EPA Recommended AERMOD Format Data

Ozone EPA Recommended Excel Format Data

For information about each of these sites please refer to ARB's Quality Assurance Air Monitoring Site Information.

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Nitrogen Dioxide Data (Only for use in performing a Tier IV or paired sums analysis)**

Select the appropriate county folder from our FTP server. Clicking on the link below will direct you to the files.

NO2 Hourly Data

NO2 3 Year Max Data

NO2 EPA Recommended AERMOD Format Data

NO2 EPA Recommended Excel Format Data

To download the District’s guidance on developing “EPA’s NO₂ Modeling Background Datasets”. Click here.

For information about each of these sites please refer to ARB's Quality Assurance Air Monitoring Site Information.

Contact the District before performing a Tier IV or paired sums analysis!

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Modeling Guidance

• District Air Dispersion Modeling Guidance
• Procedure For Determining NO2 Monitor Background Values (Design Values) For Use In Calculating NAAQS Compliance (606 kb)
• Assessment of Non-Regulatory Options in AERMOD Specifically OLM and PVMRM (552 kb)
  The District has developed an MS Access DB which implements the Tier III and Tier IV procedures outlined in the above document. The program is free of charge and is provided as is. If you would like a copy of the program please contact HRAmodeler@valleyair.org.
• District Meteorological Processing Procedures (2 mb)
• Meteorological Data Template – zip file (326 kb)
• NO₂/NO_X In-Stack Ratios
• CAPCOA 1-Hour NO2 Modeling Guidance
• DRAFT District PM2.5 Modeling Procedures

Permit Modeling Policies

• APR 1905 - Risk Management Policy for Permitting New and Modified Sources (Updated 5/28/15)
• APR 1906 - Framework for Performing Health Risk Assessments (Updated 5/28/15)
• APR 1920 - District Policy: Policy for Modeling Intermittent Operating Units When Evaluating for CAAQS/NAAQS (Updated 9/6/11)
• APR 1925 - Policy for District Rule 2201 AAQA Modeling (Updated 4/14/14)
• APR 1930 - Area Source Emissions Inventory Methodology Format (Updated 4/14/14)
• APR 1965 - Policy for determining if and how emission sources may be aggregated for modeling (Updated March 3, 2016)

Prevention of Significant Deterioration (PSD)

• PSD General Modeling Requirements - Draft (January 2014)
• APR 1940 - Policy for PSD Modeling District Rule 2410 Guidance for Determining Modeling Domain (Updated 7/25/14)
• APR 1945 - Policy for PSD Modeling District Rule 2410 Guidance for Intermittent Operating Units (Updated 7/25/14)
• APR 1950 - Policy for PSD Modeling District Rule 2410 Guidance for Identifying Sources to be Evaluated for Inclusion in a Cumulative Impact Assessment (Updated 7/25/14)
• APR 1955 - Policy for PSD Modeling District Rule 2410 Guidance for Selecting a Representative Monitoring Site(s) (Updated 7/25/14)
• APR 1960 - Policy for PSD Modeling District Rule 2410 Guidance for Identifying Sources to be Evaluated for Inclusion in an Increment Assessment (Updated 7/25/14)

Modeling Resources

All health risk assessments must comply with the Office of Environmental Health Hazard Assessment’s (OEHHA’s) guidelines. Any methodology that does not use HARP must be reviewed by ARB and/or OEHHA prior to submission to the District to ensure that OEHHA’s guidelines are fully implemented.

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