INFLUENCE OF DIFFERENT MICROPHYSICAL SCHEMES ON THE PREDICTION OF DISSOLUTION OF NONREACTIVE GASES BY CLOUD DROPLETS AND RAINDROPS

Three microphysical formulations are closely compared to evaluate thei r impact upon gas scavenging and wet deposition processes. They range from a classical bulk approach to a fully spectral representation, inc luding an intermediate semispectral parameterization. Detailed compari sons among the microphysical rates provided by these three parameteriz ations are performed with special emphasis on evaporation rate calcula tions. This comparative study is carried out in the context of a mount ain wave simulation. Major differences are essentially found in the co ntrasted spreading of the microphysical fields on the downwind side of the mountain. A detailed chemical module including the dissolution of the species and their transfer between phases (air, cloud, and rain) is coupled with the three microphysical parameterizations in the frame work of the dynamical mesoscale model. An assessment of the accuracy o f each scheme is then proposed by comparing their ability to represent the drop size dependency of chemical wet processes. The impact of eva poration (partial versus total) upon the partition of species between gas and aqueous phases is also studied in detail.