Numerical modeling of cloud and precipitation chemistry associated with two rainbands and some comparisons with observations

Precipitation growth in the narrow cold-frontal rainband (NCFR) was dominated by collection processes. The wide cold-frontal rainband (WCFR), which followed the NCFR, had most of its precipitation asssociated with frontal lifting. Surface sulfate and nitrate deposition rates predicted by the model for the WCFR were of the same order as those obtained from measurements on the ground. When the two rainbands were allowed to interact in the model, allowing the NCFR to process the air that entered the WCFR, sulfate deposition from the WCFR decreased, but nitrate deposition remained unchanged. The total sulfate deposition from the two bands, with and without interaction, differed by only ~2%. For most cases modeled, the sulfate and nitrate depositions responded approximately linearly to variations in the concentrations of the precursors. Iron-catalyzed aerobic oxidation may be an important mechanism for converting sulfur dioxide to sulfate. -from Authors