Diagnostic evaluation of regional models using chemical measurements made from aircraft

During the summer of 1988, instrumented aircraft were used to gather data aloft to be used for diagnostic evaluation of regional Eulerian acid deposition models. One mission was designed to monitor pollutant distributions during a period of frontal passage. The purpose of the flights was to develop data to evaluate how well models handle pollutant redistribution and scavenging during a frontal event, and to assess how well the models handle buildup of pollutants in a high pressure system following cold front passage. This paper compares the aircraft measurements noted above with results from the Regional Acid Deposition Model (RADM). The model results are based on simulations using a 15 layer version of RADM covering the time period of interest. The authors will discuss comparisons of model results with pollutant concentrations measured within the mixed layer and above the mixed layer. Pollutant concentrations will be compared on an absolute basis, and also on a relative basis from one flight to the next. Important comparison species include H2O2, O3, SO2, NOy, HNO3, NO2, PAN, and SO4. Of particular interest in terms of diagnostic evaluation is the model's treatment of sulfur and nitrogen chemistry. This paper will discuss sulfur and nitrogen distribution and will evaluate the influence of model vertical resolution and nighttime chemistry on this model/measurement comparison