| The importance of the roles of aerosol in modifying the atmospheric conditions has been discussed extensively. Over the last decades studies on atmospheric aerosol and its impacts have been accelerated because of a strong demand for better understanding of the atmospheric system in order to assess the impact of human activities. Although a lot of efforts, from both observations and modeling studies, have been made, there is still a lack of information of aerosol chemical composition and spatial and temporal distribution. This is due to its highly localized sources and sinks and its high variability with respect to time. In a cloudy situation, the presence of water plays a crucial role. Pre-exiting particles may nucleate water vapor to form cloud drops, and the latter will subsequently initiate complex cloud microphysical processes. The nuclei may dissolve in liquid water of cloud drops and rain. Cloud drops and rain may absorb atmospheric gases and cause further chemical reactions, resulting in the release of additional particles. This processing is called in-cloud processing. Sulfur species plays a prominent role in the in-cloud processing due to their abundance in the troposphere and high reactivity in aqueous phase.; In this study the roles of a deep convective cloud in the in-cloud processing and re-distribution of sulfate are investigated using a three-dimensional cloud/chemistry model. The model demonstrates transport of sulfur species, nucleation of sulfate particles, absorption of sulfur dioxide by water drops followed by oxidation of sulfur dioxide by hydrogen peroxide during cloud development. The study shows that (1) the main pathway of re-distributing sulfate is associated with snow although sulfate has been produced in cloud drops, (2) significant amount of sulfate got incorporated into hydrometeors via nucleation scavenging rather than via oxidation of sulfur dioxide, and (3) significant number of small particles is found in the anvil and above the updraft and these small particles are transported without being activated into cloud drops. |
