Parameterization of the Vertical Transport of Momentum by Cumulus Clouds. Part II: Application

Abstract

The parameterization theory developed in Part I is applied to compute the vertical transport of momentum by cumulus clouds for the average of six convective periods in Phase III of GATE. Special attention is paid to the role of perturbation pressure field in vertical momentum transport. Good agreement between the parameterized and the observed apparent momentum sources is obtained. In general, cumulus convection tends to decrease the vertical wind shear of the environment. It is found that the cloud-mean momentum varies significantly with height in an environment with vertical wind shear, and the pressure gradient force is mostly responsible for this variation. Sensitivity tests of the parameterization scheme show that the cloud-mean momentum obtained is fairly insensitive to some poorly represented parameters in the cloud model. Results using this scheme are compared with those using the Schneider and Lindzen scheme. Appreciable improvement is found with the use of the new scheme.