Modeling Presentations from 2011 R/S/L Modelers Workshop

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Here's a link to the main page that contains links to the individual presentations.

One thing I found interesting, and potentially useful, was a San Joaquin Valley APCD web page with expanded NO2 modeling guidance and data. For example, they've collected and reported NO2/NOx ratios from a variety of source types. The range of values is surprisingly large.

(Note: Joe attended the single day of this conference that was opened to the public.)
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October 2010 Biomass Modeling Report from RTP

This is a useful report that, among other things, provides data for in-stack ratios of NO/NO2 from wood combustion. Diane Lorenzen provided it to MDEQ to support assumptions she made in the UM boiler modeling.

Biomass Modeling Report
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Updated NO2/SO2 1-hr modeling guidance

EPA released additional guidance for modeling 1-hour NO2 NAAQS compliance 3/1/2011. It updates OLM and PVMRM policy, addresses significant contribution analyses using the SILs, and discusses how to perform cumulative analyses including the option of incorporating temporally-varying background concentrations.

It also "[r]ecommends that compliance demonstrations for the 1-hour NO2 NAAQS address emission scenarios that can logically be assumed to be relatively continuous or which occur frequently enough to contribute significantly to the annual distribution of daily maximum 1-hour concentrations based on existing modeling guidelines, which provide sufficient discretion for reviewing authorities to not include intermittent emissions from emergency generators or startup/shutdown operations from compliance demonstrations for the 1-hour NO2 standard under appropriate circumstances."

3/1/2011 Policy Memo

See this blog post for access to previous memos.

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See this article for a helpful discussion of the state of SO2 and NO2 1-hr NAAQS modeling guidance, including April updates to AERMOD and AERMET. It also talks about recent EPA guidance to states for 1-hr SO2 NAAQS attainment designation.
(added 5/20/2011, KMM)
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New NO2 Air Standards Prove Technically Challenging

This article from Trinity Consultants refers to June 28, 2010 modeling guidance from EPA (link below) that doesn't actually provide much guidance, but it does suggest an interim SIL. It also reports a SIL that NESCAUM states are using. The article discusses methods for estimating NO/NO2 ratios.

Trinity Consultants - New NO2 Air Standards Prove Technically Challenging

EPA NO2 Modeling Guidance 6/2010

NO / NO2 Ratios

Here's some background information on estimating ratios of NO and NO2:

2000 Proposed Appendix W OLM Discussion

NO2 Estimating Review

1996 EPA OLM Memo

Diesel Engine NO2 MDEQ E-mail

Updated modeling guidance

Procedures for calculating the NO2 design value for comparison to the 1-hour NAAQS. Hopefully the BEEST post processor, and maybe others, will avoid the need to do this by hand.
EPA 1-hr NO2 Modeling Guidance


Excerpt from Comments of the Air and Waste Management Association's AB-3 Meteorology Committee Regarding New Dispersion Modeling Issues: PM2.5 and 1-hour for NO2 and SO2; March 12, 2010

"We now find ourselves in a unique regulatory period in which several new modeling procedures need to be established for both a newly regulated pollutant(PM2.5) and for 1-hour probabilistic standards for NO2 in spring 2010 and for SO2 in summer 2010. Associated with these pollutants and standards are important modeling issues that are not currently addressed in the Guideline. Regulatory dispersion modeling analyses have historically employed, in practice, several assumptions used to assure a conservative estimate of the modeled design concentration. Many of these assumptions are used only to simplify the analyses in the absence of more robust, scientifically sound information about the emissions sources and atmospheric conditions that affect the ambient pollutant concentrations. With the advent of several more stringent air quality standards, it is no longer practical to use redundant, overly conservative assumptions for simplicity or convenience. We encourage the development and implementation of robust methods for conducting regulatory air quality modeling analyses."

The document is here:
AWMA PM2.5 modeling comments


Here's a memo from EPA on modeling PM2.5. Basically, it "recommends" that, when modeling five years of NWS data for compliance with the 24-hr PM2.5 NAAQS, you should add the average of the first-highest 24-hr values for all five years to the 98% percentile of background measurements for three years.

2/26 & 2/24 EPA reviews and comments re. PM2.5 modeling

This supplemental EPA PM10/PM2.5 modeling memo addresses PM10 surrogacy demonstration and provides more extensive modeling guidance for PM2.5. The way I interpret it, it suggests using the highest 3-yr average across 5 years of NWS results for the annual average. For the 24-hr average, use the highest 3-yr avg. of H1H 24-hr results across 5 years of NWS model results.

March 23rd PM2.5 modeling guidance