Effects of land-use modification on potential increase of convection: A numerical mesoscale study over south Israel

Abstract

The current research was designed to examine the potential of modified surface conditions in semiarid and arid central-southern Israel to enhance convective development and rainfall. The fifth-generation mesoscale model (MM5), coupled with a sophisticated land-surface submodel, is applied for the three-dimensional high resolution simulations of two convective rain case studies, on October 27, 1990 and October 18, 1987. Three surface conditions are modeled to examine the relative influence of land-use changes, which are present-time land-use (1990s), preirrigation time (1930s), and the hypothetical case of extended irrigated agricultural lands. The main conclusion of the study is that there exists a positive influence of the anthropogenic land-use changes on the enhancement of thermal convection and associated rainfall. Modification of surface parameters from semiarid land conditions to cultivated lands tends to consistently increase the potential for moist convection during the daytime heating hours, as expressed in the evolution of the PBL structure and the growth of convective available potential energy (CAPE), as well as the area-averaged rainfall. The model seems to accurately reproduce the observed atmospheric situations and rainfall, lending confidence to the assertion that these land-atmosphere effects can be quantified with an advanced mesoscale modeling system. This work is the first numerical mesobeta scale 3-D study over the south Israel area with its relatively sharp spatial change in land use as well as in climatic zone. It is believed to be a region, possibly the only in the world, where mesoscale surface and planetary boundary layer processes were suggested as causes for observed anti-desertification gains. Copyright 2001 by the American Geophysical Union.