Synoptic scale features associated with vertical distribution of IR aerosol extinction.

Abstract

Observed vertical profiles of optical extinction due to aerosol scattering were examined relative to prevailing synoptic scale features. This examination was on the suitability of an existing wind speed and humidity dependent extinction model during different synoptic conditions . The primary synoptic features in question are the depth of the atmospheric well mixed layer and the nature of the capping inversion. Aerosol extinction profiles were calculated from aerosol size distributions measured from an aircraft in the vicinity of Monterey Bay. Mixed layer descriptions were obtained from temperature and humidity profiles obtained from aircraft spiral ascents and shipboard and shoreline radiosonde launches. The presence of the inversion reduced the accuracies of the current Navy (Wells-Katz) and Air Force (LOVJTRAN 33)- models in estimating the extinction profile . The inversion represents a cap to the vertical transport of surface generated aerosols. This is not accounted for in the models. LOWTRAN 33 was found to be inadequate in most respects whereas the Wells-Katz model could be modified to obtain reasonable predictions. Model specification of the continental component was also found to be a significant factor in the comparisons.