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Development and evaluation of an ammonia bidirectional flux parameterization for air quality models
Author(s) -
Pleim Jonathan E.,
Bash Jesse O.,
Walker John T.,
Cooter Ellen J.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50262
Subject(s) - flux (metallurgy) , environmental science , biogeochemical cycle , deposition (geology) , atmospheric sciences , biosphere , nitrification , air quality index , nitrogen , environmental chemistry , chemistry , meteorology , ecology , geography , physics , paleontology , organic chemistry , sediment , biology
Ammonia is an important contributor to particulate matter in the atmosphere and can significantly impact terrestrial and aquatic ecosystems. Surface exchange between the atmosphere and biosphere is a key part of the ammonia cycle. New modeling techniques are being developed for use in air quality models that replace current ammonia emissions from fertilized crops and ammonia dry deposition with a bidirectional surface flux model including linkage to a detailed biogeochemical and farm management model. Recent field studies involving surface flux measurements over crops that predominate in North America have been crucial for extending earlier bidirectional flux models toward more realistic treatment of NH 3 fluxes for croplands. Comparisons of the ammonia bidirection flux algorithm to both lightly fertilized soybeans and heavily fertilized corn demonstrate that the model can capture the magnitude and dynamics of observed ammonia fluxes, both net deposition and evasion, over a range of conditions with overall biases on the order of the uncertainty of the measurements. However, successful application to the field experiment in heavily fertilized corn required substantial modification of the model to include new parameterizations for in‐soil diffusion resistance, ground quasi‐laminar boundary layer resistance, and revised cuticular resistance that is dependent on in‐canopy NH 3 concentration and RH at the leaf surface. This new bidirectional flux algorithm has been incorporated in an air quality modeling system, which also includes an implementation of a soil nitrification model.