Chapter 20 Cloud system modeling

Abstract

This chapter provides an overview of the cloud system modeling. Cloud-resolving models (CRMs) are numerical models that explicitly represent the cloud-scale circulations and their interactions with microphysical, radiative, and small-scale turbulent processes. Most CRMs are two-dimensional (2-D) models, which allow them to simulate the mesoscale organization of cloud systems over multiday time periods. In contrast, three-dimensional (3-D) large-eddy simulation models are limited to simulating large turbulent eddies over periods of several hours, and one-dimensional (1-D) column models must parameterize the cloud-scale circulations as well as the turbulence. Two-dimensional CRMs are used to study a variety of cloud types and systems. The scales of motion that are explicitly represented depend on the cloud system of interest. The time scales and space scales of a CRM used to simulate a convective cloud system to those of global climate models (GCMs) are compared. The effects of scales of motion that are not resolved are parameterized using a turbulence closure. The chapter explains that new observations of clouds will allow more thorough evaluations of the microphysical and radiative transfer parameterizations employed in CRMs.