Influence of soil moisture on the Sahelian climate prediction II

Summary The sensitivity of short-term climate to soil moisture parameterization has been investigated using the Florida State University Global Spectral Model. This is done through the implementation of a simple and realistic soil moisture availability in a prognostic equation for the surface temperature.The results from two seasonal simulations between 11 May and 31 August 1979 are discussed with an emphasis on the Sahelian regions. These experiments indicated that most of the significant changes that resulted from the new parameterization occurred at and near the surface. Above the surface, land surface effects were strongly diffused and for most of the cases were not conclusively discernible. At the surface, however, soil moisture appeared to be a parameter of large influence. Important modulations in the surface temperature were obtained. The time dependence of the soil moisture availability has led to an evolution of the surface heat sources in the model resulting in an apparent northward propagation of the centers of maximum temperature as the rainfall season progressed over the north African continent from May to August. This has had an important effect on the distribution of the primary variables and showed significant departures from the control.The interaction introduced by the new scheme between the physical processes parameterized in the model, has resulted in a differential modification of the rainfall distribution, and the changes in the hydrological cycle have remarkably affected the summer Sahelian rainfall.With 20 Figures