1. Institute of Earth Sciences, The Multi-Disciplinary Center for Environmental Research, Faculty of Agriculture, and Department of Geography, The Hebrew University of Jerusalem, Israel, CNRS 132, CEREGE, Universite Aix-Marseille III, 13545 Aix en Provence Cedex 4, France, and University of Athens, Laboratory of Meteorology, Ippocratous 33, Athens 10680, Greece