重力波動對層積雲系統垂直結構及雲量之影響

Abstract

This study aims to understand the impacts of gravity waves on the cloud fraction and vertical structures of stratocumulus topped boundary layer (STBL) under two strat-ocumulus regimes. The impact of such gravity waves on STBL is investigated using a high-resolution vector vorticity equation based cloud resolving model (VVM) (Jung and Arakawa 2008; Wu and Arakawa 2011) by adding large-scale convergence that mimics observed mesoscale semidiurnal waves. The results show that the wave induced vertical velocity causes STBL to become decoupled. During the ascending phase, the cloud is lifted and thickens. With larger cloud amount, Entrainment-Liquid Flux feedback (ELF) starts to adjust by enhancing cloud top entrainment and cloud base warming, which causes STBL to become decou-pled. Furthermore, the results show that the vertical structure and cloud fraction at the end of simulation is largely determined by the sea surface fluxes. The experiment with weaker surface fluxes causes STBL to break up by limiting Surface-based Mixed Layer (SML) cumuliform clouds.