Invited Presentation: On the locality of smoke semi-direct effect and indirect effect

The past decade has seen much improved characterization of processes related to smoke semi-direct and indirect effects. These characterizations have advanced our understanding beyond the early concepts that light absorption by smoke particles hinders cloud development, or cloud particles size decreases as the loading of smoke particles increases. However, many proposed new concepts and processes sometimes are against to each other in terms of their effects on cloud lifecycle and cloud microphysics, reflecting potential confounding factors especially related to local meteorology that regulates the dynamics and thermal dynamics of atmosphere surrounding the aerosols and clouds. In this talk, we will highlight the importance of meteorology to the final outcomes of smoke-cloud interactions. We will show cases where smoke from Central America may have enhanced the severe storms over the southeast United States, and other examples where smoke above the persistent clouds over Asian maritime continents may trigger secondary circulations, leading to the complicated feedbacks on the change of atmospheric lapse rate. In each of these cases, we combine satellite observation and meso-scale models to illustrate that the relative role of smoke semi-direct and indirect effect highly depends on the local meteorology including boundary layer processes, topography, sea and land breeze (if applicable). In particular, control for the location of clouds relative to the surrounding synoptic and meso-scale systems is critical. A full understanding of smoke-cloud interaction hence requires a process-oriented approach with local meteorology taken account to explain the causal and effect relationships.