Improved estimates of the North American atmospheric reactive nitrogen budget using chemical transport models, surface measurements, and space-based observations of NH3 and NO2
Abstract
Because the processes that govern the fate and transport of reactive nitrogen are intertwined with the natural world, quantifying the sources and sinks remains an important challenge. Chemical-transport models are an important tool in understanding these relationships, but they are limited by gaps in our knowledge of emission sources. Two key uncertainties are the temporal and spatial distribution of ammonia emissions from agriculture and the intensity and vertical distribution of nitrogen oxide from lightning. Major factors in agricultural ammonia emissions are farming practices and meteorology. To properly challenge the model estimates of ammonia concentration, we compare with several different gas-phase ammonia surface measurement stations. Each site has a different temporal distribution of concentrations due to differences in dominant ammonia source. These surface measurements are compared with CMAQ simulations from 2002 - 2006 and NH3 near surface mixing ratio retrieved from the TES instrument. State-of-science emission estimates and modeling tools are not able to capture the temporal variability, which suggests that spatially comprehensive, space-based measurements of NH3 could improve ammonia emission estimates considerably. Second, we have implemented an improved lightning NOx emission scheme in CMAQ and evaluated it using measurements of NOx aloft and SCIAMACHY NO2 column densities during the summer of 2004. We find that this geogenic source of nitrogen oxide is an important part of the reactive nitrogen budget in the summer, and properly representing this source helps close the gap between modeled and measured nitric acid wet-deposition fluxes. These improved modeling tools are used to quantify the atmospheric reactive nitrogen budget over North America and the Midwestern United States.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.A34A..08P
- Keywords:
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- 0330 ATMOSPHERIC COMPOSITION AND STRUCTURE / Geochemical cycles;
- 0345 ATMOSPHERIC COMPOSITION AND STRUCTURE / Pollution: urban and regional;
- 3355 ATMOSPHERIC PROCESSES / Regional modeling;
- 3360 ATMOSPHERIC PROCESSES / Remote sensing