Numerical Experiments on Land Surface Alterations with a Zonal Model Allowing for Interaction between the Geobotanic State and Climate

Abstract

A zonally-averaged steady-state hemispheric mean-annual climate model is used for conducting a series of experiments on land surface alterations: desertification, deforestation and irrigation. In each experiment a fixed perturbation of surface albedo and water availability is imposed in a single latitude belt (but a different perturbation is specified in each experiment). The desertification and deforestation experiments simulate modifications to the geobotanic state due to destruction of vegetation by overgrazing and excessive cultivation of the land in the semiarid and tropical zones, respectively. The irrigation experiment simulates the climatic impact of massive irrigation of the desert belt. Results indicate that the effect of changes in evapotranspiration rather than in surface albedo is predominant in regulating the surface temperature. It is shown that the impact of biofeedback is strongest in the area adjacent to the perturbation zone. It is also concluded that the prescribed perturbations of the geobotanic state are not sufficient to modify climate to an extent that these perturbations would persist.