EFFECTS OF A POLYDISPERSE CLOUD ON TROPOSPHERIC CHEMISTRY

Effects of a polydisperse cloud on tropospheric chemistry have been st udied in the framework of a two-dimensional model where dynamical, mic rophysical, and chemical processes are fully interactive. The chemical module describes the tropospheric photochemistry of ozone precursors in both gaseous and aqueous phases for a remote atmosphere. Impacts of the cloud polydisperse feature have been obtained by comparing the re sults in the ease of a monodisperse cloud created under the same meteo rological conditions. The [NO]/[NO2] ratio decreases more sharply in t he case of the polydisperse cloud. The partitioning of the most solubl e species does not follow the Henry's law equilibrium except in the mi ddle of the cloud. This result has implications for airborne measureme nts made within clouds. Deviations from Henry's law found in samples a re usually explained only by the effect of variations of the liquid wa ter content with time, assuming that no real deviations exist in the r eal cloud. Here, it is shown that deviations from Henry's law equilibr ium may exist even for clouds consisting of small droplets.