ON THE RESPONSE OF THE TROPICAL ATMOSPHERE TO LARGE-SCALE DEFORESTATION

Recent studies on the Amazon deforestation problem predict that remova l of the forest will result in a higher surface temperature, a signifi cant reduction in evaporation and precipitation, and possibly signific ant changes in the tropical circulation. Here, we discuss the basic me chanisms contributing to the response of the tropical atmosphere to de forestation. A simple linear model of the tropical atmosphere is used in studying the effects of deforestation on climate. It is suggested t hat the impact of large-scale deforestation on the circulation of the tropical atmosphere consists of two components: the response of the tr opical circulation to the negative change in precipitation (heating), and the response of the same circulation to the positive change in sur face temperature. Owing to their different signs, the changes in predi cted temperature and precipitation excite competing responses working in opposite directions. The predicted change in tropical circulation d etermines the change, if any, in atmospheric moisture convergence, whi ch is equivalent to the change in run-off. The dependence of run-off p redictions on the relative magnitudes of the predicted changes in prec ipitation and surface temperature implies that the predictions about r un-off are highly sensitive, which explains, at least partly, the disa greement between the different models concerning the sign of the predi cted change in Amazonian run-off.