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SEASONAL NH 3 EMISSIONS FOR ANNUAL 2001 CMAQ SIMULATION: INVERSE MODEL ESTIMATION AND EVALUATION
Citation:
Gilliland, A B., S J. Roselle, R. Pender, AND R L. Dennis. SEASONAL NH 3 EMISSIONS FOR ANNUAL 2001 CMAQ SIMULATION: INVERSE MODEL ESTIMATION AND EVALUATION. Presented at 2004 Models-3 Conference, Chapel Hill, NC, October 18-20, 2004.
Impact/Purpose:
The goal of this task is to thoroughly characterize the performance of the emissions, meteorological and chemical/transport modeling components of the Models-3 system, with an emphasis on the chemical/transport model, CMAQ. Emissions-based models are composed of highly complex scientific hypotheses concerning natural processes that can be evaluated through comparison with observations, but not validated. Both performance and diagnostic evaluation together with sensitivity analyses are needed to establish credibility and build confidence within the client and scientific community in the simulations results for policy and scientific applications. The characterization of the performance of Models-3/CMAQ is also a tool for the model developers to identify aspects of the modeling system that require further improvement.
Description:
The formation of ammonium nitrate aerosols is often limited by ammonia (NH3), and sulfate aerosols are predominantly in the form of ammonium sulfate. While NH3plays a central role in the prediction of nitrate and sulfate aerosols, inherent uncertainty exists in NH3 emissions because of the predominant sources, animal husbandry and fertilizer application. The temporal variability in fertilizer application and the meteorological dependence of NH3 volatilization from animal waste suggest that a strong seasonal variability should be expected in the emissions. Current work by Pinder et al. [2004] provides the first farm-level model for NH3 emissions from dairy cattle, and Goebes et al. [2003] provides a seasonally varying fertilizer inventory for NH3. Top-down estimates of NH3 seasonally varying emissions for all combined source types have been developed by Gilliland et al. [2003] using an inverse modeling method. Currently, these studies provide the most comprehensive information available for seasonally distributing NH3 emissions for air quality modeling. Combining this information, we have constructed a best prior estimate of seasonal scaling factors for NH3 emissions. These emissions were then used in an annual 2001 simulation using the USEPA Community Multiscale Air Quality (CMAQ) model for a contiguous United States domain. The objective of this study is to evaluate the reasonableness of these prior NH3 emission scaling factors and then test the inverse modeling method used to produce revised top-down seasonal scaling factors for the modeling domain. First, we will describe the approach used to generate our best prior estimate of NH3 seasonal scaling factors. Evaluation results against the National Atmospheric Deposition Program (NADP) precipitation chemistry network and several speciated aerosol networks will then be presented with a primary focus on monthly and seasonal time scales. Posterior inverse modeling emission estimates will be presented to conclude the analyses.
The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies or views.