Microphysical-macrophysical Interactions in Marine Stratocumulus

Download or read book Microphysical-macrophysical Interactions in Marine Stratocumulus written by Xiaoli Zhou and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The extensive shallow marine stratocumulus over the eastern subtropical oceans is one of the most important cloud systems owning to their significant cooling effect on the Earth's radiation budget. Due to insufficient understanding of the key processes governing its behavior, stratocumulus remains misrepresented in climate models. The response of stratocumulus to changes in atmospheric aerosols modifies cloud microphysics, modulates precipitation, entrainment, and dynamics, which in turn regulates cloud macrophysical processes. This is referred to as the microphysical-macrophysical interactions. A better understanding of this process helps determine cloud radiative properties that impact climate. This dissertation provides a process-level understanding of microphysical-macrophysical interactions of marine stratocumulus on the synoptic scale and on the mesoscale via numerical simulations. On the synoptic scale, when advected by the trade winds from the subtropics toward the equator, stratocumulus thins and eventually breaks up to low-coverage cumulus as a result of warming sea surface temperature (SST). The trade winds also transport continental air masses downstream which often contain solar-absorbing aerosols from biomass burning. In this dissertation, we employ large-eddy simulations to investigate the impact of solar-absorbing aerosol layers on such cloud transition. On the mesoscale, stratocumulus clouds have been consistently observed to organize in either closed-cellular (dim walls, bright centers) or open-cellular (bright walls, dim centers) structures on horizontal scales of 10-50 km, yet no complete theory on the mechanism for the scale of open and closed cells has appeared in the literature. Here numerical experiments are designed to investigate the relation between cloud scale and aerosol loading, as well as the mechanism behind it. " --