The impact of deforestation on the hydrological cycle in the western Mediterranean: an ensemble study with two regional climate models

A deforestation experiment is performed over the western Mediterranean, app lying two different RCMs with differing domains and an ensemble technique t o obtain a measure of their internal variability. The internal variability is used to assign statistical significance to the results, and also to disc uss whether the models are sufficiently free to develop internal mesoscale processes. Considerable internal variability values found for hydrological variables even in autumn and winter seem to support the assumption that the models are free enough to be applied to such a sensitivity study. The comb ined use of two models, with strongly differing domains, and significance a ssigned through the use of internal variability should highlight responses to deforestation which are of physical origin and not a result dependent on one particular model. The overall significant response from both RCMs to d eforestation is a reduction of evaporation (spring and summer, extending ov er the whole deforested zone) and a decrease in precipitation (late spring and summer, over some regions). A detailed analysis over subzones shows rem arkable agreement between the two models ever some of these subzones, showi ng non-local effects in precipitation response.