Investigation of the Effects of Aerosol Regeneration on Marine Stratocumulus Cloud Development with WRF-LES

Marine Stratocumulus cloud (MSC) has wide extent and long lasting life time in subtropical region. Understanding MSC is important for estimating more accurate cloud radiative forcing. Large Eddy Simulation (LES) models are appropriate tools for studying characteristic of MSC. Because LES models can explicitly resolve microphysical, dynamical and radiative processes and their interactions of MSC in a realistic way. In this study, we try to focus on the aerosol regeneration process after droplet evaporation. Because of the inversion layer covering cloud top, droplet evaporation due to entrainment of dry air above exerts a large impact on the development of MSC. Nevertheless, there is no aerosol regeneration process after droplet evaporation in the spectral bin microphysics (SBM) scheme of Weather Research and Forecasting (WRF)-LES. In this study we develop aerosol regeneration method and implement it in the SBM scheme. After cloud droplets are formed, they go through many processes like diffusional growth, partial evaporation, collision, coalescence and breakup. Therefore it is difficult to know the accurate sizes of regenerated aerosols. So we try to find what type of regenerated aerosol spectrum produces more realistic results by comparing them with the observational data obtained from the aircraft measurement of marine stratocumulus clouds during the Variability of the American Monsoon System Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). Finally we investigate how the aerosol regeneration affect the evolution of cloud and precipitation.