On Some Meteorological Patterns in the Dead Sea Area during Advective Sharav Situations

Wind, temperature and moisture fields, as well as evaporation rates for the advective sharav condition, were simulated along the Dead Sea region. The possible effect of the stable thermal atmospheric stratification on evaporation patterns over the Dead Sea is discussed. This contribution concludes a series of mesoscale modelling studies over Israel. Further refinements of the current model to be considered subsequently are outlined. Introduction The proposed construction of a ~hannel carrying water from the Mediterranean to the Dead Sea, for generation of electric power (Weiner, 1980), motivated the model analysis presented here. Evaluation of evaporation rates from the lake, while considering the temporal and spatial character of the pertinent meteorological fields, is a crucial component of such a project. Such an evaluation can be achieved by determining the contributions of the most frequent climatic situations in the Dead Sea area to evaporation. Previous studies evaluating the meteorological patterns in this area focused on the two most significant seasons, summer and winter (observational studies by Ashbel (1939) and Bitan (1974, 1977) and the numerical model study by Segal et al. (1983)). The current contrib~tion evaluates a less prevalent situation -the advective sharav. This synoptic situation, which is associated with a dry and warm easterly flow over the region, is frequent during the fall and spring (for a general description see Levi (1967) and Winstanley (1972)). A schematic illustration of surface pressure systems during such conditions is given in Figure 1. During these conditions, a distortion of the regular daily cycle of thermally induced circulations is typical. The onset of a very intense, stable marine layer when a warm flow moves over a cooler water body was indicated in a previous *Perrnanent affiliation: The Seagram Centre for Soil and Water Sciences, The Hebrew University of Jerusalem, Faculty of Agriculture, P.D.B. 12, Rehovot 76100 Israel Received May 22, 1983 and in revised form November 23, 1983 DEAD SEA ADVECTIVE SHARA V 77 31£ 36£ j;~~~=~~.!Z:: 4 'H ,% I~~ ~::c-;~ I I ::. ---"~ "'".,.",," approximation for the model may cause some intensification of the simulated flow in the vicinity of the lake area as compared with reality (Alpert et al., 1982; Segal et al., 1983). However, it has the advantage of enabling the use of fine grid resolution over the lake area, which becomes expensive when applied in a 3-D model. Verification studies for this model over irregular terrain (e.g. Mahrer & Segal, 1979b; Mizzi, 1982; Segal et al., 1982), however, indicate reasonable accuracy of prediction even with those assumptions. 31£ 36£ '\1 ,}!-* ilI H:!) I 'i\.. ,~~I --r -"," f I ~~ I <' :..~ :5 ;] ~.. i :.; , '" .. "