On midlatitude cyclonic cloud systems, large scale models and feedbacks

R.E. Stewart

Proc. GCSS/WGNE Workshop. Cloud Processes and Feedbacks of Large-Scale Models
ECMWF, Reading, UK, (In press).

Abstract

Midlatitude cyclonic cloud systems commonly occur and they significantly impact our climate. They must therefore be properly handled within large-scale models. In particular, several aspects of these cloud systems must be properly addressed including their atmospheric forcing response, internal structure, surface interactions, cloud layering, microphysics, precipitation, water cycling and radiation. Efforts within the Extratropical Layer Clouds Working Group of GCSS are concentrating on typical cases of these systems within major storm tracks and with varying large-scale forcing and surface conditions. Preliminary modelling results have, for example, documented inadequacies in accounting for all the critical low, middle and high clouds within these systems; it is also apparent that such cloud layering features must be addressed collectively because they are strongly coupled. In general, these cyclonic cloud systems are very sensitive to background conditions, and feedbacks with large scales occur through several processes.