报告题目：Improvements on climate simulation with multi-scale framework

报告人：Anning Cheng

单位：Science Systems and Applications, Inc., Hampton, VA and Climate Science Branch, NASA Langley Research Center, Hampton, VA

时间：2012年1月11日上午10:00(星期三)

地点：中关村二楼会议室

摘要：

A promising approach to climate modeling and prediction is the Multi-scale Modeling Framework model (MMF). This approach replaces all cloud parameterizations of a conventional general circulation model (GCM) with a cloud-system resolving model (CRM) at every GCM grid. CRMs explicitly simulate the circulations associated with mesoscale convective cloud systems. The sub-CRM grid-scale is parameterized by either low-order turbulence closure, or explicitly resolved with a large-eddy simulation (LES). Each component of MMF, i.e. GCM, CRM and LES, can be tested offline independently to study specific problem, such as radiative and microphysical processes and convectively generated gravity waves. The MMF approach, as a unified system, can produce the Madden–Julian oscillation, higher-frequency tropical waves and diurnal cycles of precipitation in a much more realistic manner than a GCM with a traditional cloud parameterization. Furthermore, This study presents an upgrade of the MMF in which the first-order turbulence closure scheme is replaced by an advanced third-order turbulence closure in its CRM component. The results are compared between the upgraded and original MMFs, the host GCM, and observations. The global distributions of low-level cloud amounts in the subtropics in the upgraded MMF show substantial improvement relative to the original MMF when both are compared with observations. The improved simulation of low-level clouds is attributed not only to the representation of subgrid-scale condensation in the embedded CRM, but also closely related to the increased surface sensible and latent heat fluxes, the increased lower tropospheric stability and stronger longwave radiative cooling.