Changing Aerosol Properties with Distance to Cloud; Is It an Artifact or Reality?
Abstract:Many aerosol studies based on remote sensing data reported changes in aerosol properties as a function of distance to cloud and/or cloud cover. For example, most satellite observations show a positive correlation between aerosol optical depth (AOT) and cloud cover. Part of this correlation is due to remote sensing artifacts resulting from (1) our inability to distinguish between aerosols and weak cloud elements, and (2) cloud-related 3D radiative effects. In turn, the correlation between aerosol properties and cloud cover influences aerosol statistics calculated as a function of distance to cloud. Indeed, far-from-cloud aerosol statistics is dominated by data from scenes with lower cloud fractions, while near-cloud aerosol statistics is dominated by data from scenes with higher cloud fractions. From the other hand, part of the near-cloud enhancement in AOT is due to aerosol hygroscopic growth in the humid environment surrounding clouds.
In this paper we overview the current understanding of possible remote sensing artifacts. We discuss how these artifacts can be mitigated and corrected by combining observations from several A-train instruments, thus helping to quantify the changes of aerosol properties in the vicinity of clouds.