Impact of mesoscale organizations and precipitation on boundary-layer clouds

Description

ARM observations and the observations collected from other field campaigns often show that the evolution of boundary-layer clouds is not only controlled by the boundary layer-processes but also strongly affected by cloud mesoscale organizations and precipitation processes. Although cloud mesoscale organizations and rainfall can be readily detected by the advanced remote sensing instruments, the impact of mesoscale organizations and precipitation on cloud fields and the vertical transport induced by the boundary-layer clouds cannot be quantified solely from observations since some of the variables needed for such quantifications cannot be measured directly by the existing instrumentation. In this study, we reproduced cloud mesoscale organizations and simulated precipitation using multiple-scale WRF simulations. To quantify (or separate) the effects of mesoscale organizations from a rich range of scales involved with boundary-layer clouds, a novel approach, 2D wavelet transform (WT), was used to decompose the simulated cumulus fields and determine the individual effects from the processes with different scales. The analyses show that the cloud mesoscale organizations can substantially affect the vertical fluxes and energy associated with boundary-layer clouds. The significant impact of cloud mesoscale organizations suggests that the effects of mesoscale organizations need to be considered in boundary-layer cloud parameterizations. Our sensitivity tests on precipitation also show that precipitation can modulate cloud vertical turbulent structure and cloud mesoscale organizations.