RECENT CHANGES IN THE CLIMATE AT THE DEAD SEA – A PRELIMINARY STUDY P. ALPERT and H. SHAFIR Department of Geophysics and Planetary Sciences, Tel-Aviv University, Israel 69978 D. ISSAHARY Dead Sea Works, Research Department, South Dead Sea, Israel Abstract. In the last decade pan evaporation measured at the Southern Dead Sea has significantly increased. Wind, temperature and humidity measurements at the Dead Sea starting in the 1930s as well as 3-D model simulations all seem to indicate a statistically significant change in the local climate of the Dead Sea region. The potential contribution to this climatic change through the weakening of the local land-sea breeze circulation caused by the reduction in the Dead Sea surface area in 1979–1981, is examined. It is suggested that since the breeze tempers the Dead Sea climate, its weakening has caused the air temperature to increase, the relative humidity to decrease and thus increased the pan evaporation. The climatic changes as implied by the MM4 Mesoscale PSU/NCAR model simulations, seem to fit the observed changes and to suggest a local tendency to the more arid climate that now prevails to the south of the study region. 1. Introduction The Dead Sea has attracted attention from ancient times as it does today; it is located at the lowest spot on the earth; currently, about –410 m below sea level. It is a part of the Rift Valley, extending from the Taurus mountains in Turkey to East Africa. Its waters are the densest and saltiest of any natural water body, and gave the Dead Sea its name, as almost no form of life higher than bacteria exists in this water, see Oren (1993). The potash factory, located on the southern part of the lake, makes use of the concentrated salts and the arid climate to manufacture potash, bromine and other salts by natural evaporation. The arid climate provides high values of evaporation which make the production process successful. It is this special Dead Sea climate which is the focus of this paper. The pio- neering studies of the Dead Sea climate were those of Ashbel, who made extensive measurements of meteorological as well as hydrological parameters starting in the 1930s; these were summarised in Ashbel (1975). In recent years, Bitan (1974) has investigated special features of the Dead Sea wind regimes. Recently, Israel and Jordan have made extensive use of the water previously flowing into the Dead Sea. As a result, parts of the Dead Sea have dried. Stein- horn (1981), Klein (1982), Anati and Shasha (1989) and others investigated these changes in the area of the Dead Sea from different points of view. One result has been the separation of the Northern basin of the Dead Sea from the Southern basin which only continues to exist artificially as a water surface with a depth of only 1–2 m, and is used as an evaporation pond for the Work partly done while on Sabbatical Leave at Data Assimilation Office, Code 910.3, NASA/GSFC, Greenbelt, MD20771. Climatic Change 37: 513–537, 1997. c 1997 Kluwer Academic Publishers. Printed in the Netherlands.