A SOIL-MOISTURE RAINFALL FEEDBACK MECHANISM 2 - NUMERICAL EXPERIMENTS

Here we develop a numerical model to investigate the hypothesis propos ed by a companion paper [Eltahir, this issue], which describes a soil moisture-rainfall feedback mechanism. The model is designed to describ e the seasonal evolution of the West African monsoon rainfall and is u sed to perform numerical experiments that elucidate the mechanisms of the response of rainfall to soil moisture anomalies. A significant rai nfall anomaly is simulated by the model in response to a hypothetical soil moisture anomaly that has been imposed during early summer. Howev er, the magnitude of this anomaly almost vanishes when the net radiati on at the surface is not allowed to respond to the soil moisture anoma ly. Hence the results of the numerical experiments support the propose d hypothesis and highlight the crucial importance of the radiative and dynamical feedbacks in regulating the rainfall anomalies that result from the soil moisture anomalies.