TITLE:
Model-Measurement Comparison of Ammonia Bi-Directional Air-Surface Exchange Fluxes over Agricultural Fields
AUTHORS:
Zhuanshi He, Lorraine Paige Wright, Leiming Zhang
KEYWORDS:
Air-Quality Model; Dry Deposition; Soil Emission; Model Evaluation
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.3 No.4,
September
6,
2013
ABSTRACT: Modeled and measured bi-directional
fluxes (BDFs) of ammonia (NH3) were compared over fertilized soybean
and corn canopies for three intensive sampling periods: the first, during the
summer of 2002 in Warsaw, North Carolina (NC), USA; and the second
and third during the summer of 2007
in Lillington, NC. For the first and the third
experimental periods, the BDF model produced reasonable diurnal flux patterns.
The model also produced correct flux directions (emission and dry deposition)
and magnitudes under dry and wet canopy conditions and during day and nighttime
for these two periods. However, the model fails to produce the observed very
high upward fluxes from the second sampling period due to the fertilization
application (and thus being much higher soil emission potentials in the field than the default
model values), although this can be improved by adjusting model input of soil
emission potentials. Model-measurement comparison results suggest that the
model is likely capable for improving long-term or regional scale ammonia predictions
if implemented in chemical transport models replace the traditional dry deposition models,
although modifications are needed when applying to specific situations.