Atmospheric Modeling and Analysis Research
Bidirectional Air-Surface Exchange
The flux of atmospheric pollutants and precursors to atmospheric pollutants follow the same air-surface exchange mechanisms as the surface fluxes of heat, moisture and momentum and are also influenced by the physical, chemical, and biological properties of the surface (Hicks et al, 1987).
These fluxes are typically parameterized in air-quality models as the product of the ambient atmospheric concentration and the dry deposition velocity. The use of the dry deposition velocity concept is only valid for chemical species with no sources at the land or sea surface. Measurements have shown that some atmospheric trace gasses (including amonia, nitric oxide, and mercury) can emit from wide spread area sources due to wide spread anthropogenic activity, atmospheric deposition and biogeochemical processes.
EPA's Community Multiscale Air Quality (CMAQ) model is being developed to capture amonia, nitric oxide, and mercury fluxes at terrestrial and surface water sources to better characterize the transport and fate of these atmospheric pollutants.
Figure 1. Diel hourly box plots of observations from the June 18 - August 24, 2002 flux measurements over a soybean canopy at Warsaw, N.C., in green, paired with CMAQ box model results, red. The 5th and 95th quantiles are represented by the whiskers, the 25th and 75th quantiles are enclosed in the box. The median is represented by the horizontal line through the box and the mean is represented by the black triangle.
Hicks, B.B., Baldocchi, D.D., Meyers, T.P., Hosker, R.P., Matt, D.R.; 1987, A preliminary multiple resistance routine for deriving dry deposition velocities from measured quantities, Water, Air, and Soil Pollution 36, 311-330
- Bash, J.O., 2010, Description and initial simulation of a dynamic bi-directional air-surface exchange model for mercury in CMAQ, J. Geophys. Res.(abstract)
- Bash, J.O., Walker, J.T., Katul, G.G., Jones, M.R., Nemitz, E., Robarge, W., 2010, Estimation of in-canopy ammonia sources and sinks in a fertilized Zea Mays field, Environmental Science & Technology 44, 1683-1689 (abstract)
- Cooter, E.J., Bash, J.O., Walker, J.T., Jones, M.R., Robarge, W., 2010, Estimation of NH3 bi-directional flux over managed agricultural soils, Atmos. Environ. 44, 2107-2115
- Bash, J.O., Walker, J.T., Jones, M.R., Estimates of in-canopy ammonia sources and sinks using measured profiles and turbulence closure models (platform presentation). National Atmospheric Deposition Program Annual Meeting, Madision, WI, 14-16 October, 2008.
- Walker, J.T., Jones, M.R., Bash, J.O., Myles, L., Luke, W., Meyers, T.P., Robarge, W., Air-surface exchange of ammina in a fertilized corn canopy from planting through senescence (poster presentation). National Atmospheric Deposition Program Annual Meeting, Madision, WI, 14-16 October, 2008.
- Jones, M.R., Walker, J.T., Bash, J.O., Myles, L., Luke, W., Meyers, T.P. Robarge, W., Intercomparison of techniques to measure NH3 concentrations ad fluxes above a fertilized corn field (poster presentation). National Atmospheric Deposition Program Annual Meeting, Madision, WI, 14-16 October, 2008.