Measurements of ammonia fluxes from agricultural soils receiving supplemental fertilizer applications have demonstrated that agricultural management practices influence the magnitude, direction, and temporal patterns of emission and deposition. The 2012 release of the Community Multiscale Air Quality (CMAQ) model version 5.0 captures these observations by including an option for coupling national simulations of agricultural practices using the USDA's Environment Policy Integrated Climate (EPIC) model with CMAQ to estimate NH3 emissions from fertilizer application and to improve parameterization of the bidirectional air-surface exchange of NH3. This coupled modeling system results in improved evaluations against reduced nitrogen wet deposition and ammonium aerosol observations. Bidirectional NH3 exchange reduced the continental US annual total N deposition estimates in CMAQ by 5%, but resulted in much larger regional deposition changes. The coupled model continues to be refined and updated, and recent enhancements and updated results will be presented.

Estimation of national-scale bidirectional ammonia flux using a coupled air quality and farm management modeling system

244th National Meeting (2012)

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