Abstract
As an approach to study the interaction between the cumulus convection and the large-scale motion, a numerical experiment is performed with the use of a sufficiently fine space resolution by which the behavior of individual cumulus clouds as well as the evolution of large-scale motions can be explicitly described. For computational limitations a rectilinear two-dimensional model is adopted in which both cloud-scale and large-scale motions are uniform in one horizontal direction. We deal with a mesolike disturbance such that the horizontal scale of a large-scale ascending area where cumulus clouds are formed is only several tens of kilometers. Some cloud-microphysical processes such as autoconversion, collection and so on are incorporated, using parameterizations which have been adopted in many numerical experiments on precipitating clouds in recent years. Buoyancy perturbations are given initially so that cumulus clouds may be initiated and thereby a large-scale meridional circulation is induced.
The time integration indicates that cumulus clouds are formed one after another in the large-scale convergence field and that the large-scale circulation is intensified and maintained by the effects of cumulus clouds for a period of about 15 hours. The time variation of the large-scale field and the processes of formation, growth and decay of many individual cumulus clouds are presented and discussed.
