Aerosol effects on the cloud-field properties of tropical convective clouds
Abstract. Aerosol effects on condensed water and precipitation in a tropical cloud system driven by deep convective clouds are investigated for two-dimensional simulations of 2-day duration. Although an assumed 10-fold increase in aerosol concentration results in a similar temporal evolution of mean precipitation and a small (9%) difference in cumulative precipitation between the high- and low-aerosol cases, the characteristics of the convection are much more sensitive to aerosol. The convective mass flux, and temporal evolution and frequency distribution of the condensed water path WP (sum of liquid- and ice-water paths) differ significantly between unperturbed and aerosol-perturbed simulations. There are concomitant differences in the relative importance of individual microphysical processes and the frequency distribution of the precipitation rate (P). With increasing aerosol (i) the convective mass flux increases, leading to increases in condensation, cloud liquid, and accretion of cloud liquid by precipitation; (ii) autoconversion of cloud water to rain water decreases; (iii) the WP spatial distribution becomes more homogeneous; and (iv) there is an increase in the frequencies of high and low WP and P, and a decrease in these frequencies at the mid-range of WP and P. Thus, while aerosol perturbations have a small influence on total precipitation amount, for the case considered, they do have substantial influence on the spatiotemporal distribution of convection and precipitation.