depend on several factors, i.e., wind speed and direction,
humidity, ambient temperature, ceiling height and monitoring
location, including wet and dry depositions of NO2
and the reactions of NO2 with O3 and VOCs to secondary
PM. Not all of these factors were effectively simulated
by the model, and therefore the model simulation of the
measurements may not be totally accurate. The simulation
results at receptors greater than 5 km away from the
reference point (e.g., the receptor 11 in the target area)
were especially problematic, and it would be uncertain if
the US EPA distance threshold of 50 km was applicable
for the complex terrain and wind fields of this tropical
setting. In short, the current application of the AERMOD
is limited due to the following reasons: (1) there is no
module for NO2 deposition reactions; (2) model output is
considered on a 1-hr average time scale instead of longer