Simulations of the summer hydrometeorological processes of Lake Kinneret

Lake Kinneret is a 168-km(2) lake located in northern Israel. It provides a bout 50% of the drinking water consumed in this arid country. To manage cor rectly this vital water resource, it is essential to understand the various hydrometeorological processes that affect its water budget and, in particu lar, its evaporation. The complexity of the terrain in this region (varying from approximate to 2800 m to approximate to-410 m within a short distance ), combined with different types of soil and ground covers surrounding the lake, results in complicated microscale and mesoscale atmospheric motions, including sea, lake, and land breezes, as well as anabatic and katabatic wi nds. The Regional Atmospheric Modeling System (RAMS), a state-of-the-art no nhydrostatic model with two-way interactive multigrid nesting and four-dime nsional data assimilation capabilities, was used, together with observation s collected near the western and eastern shores of the lake, to study these processes. It was configured with two nested grids centered in the middle of the lake: 1) a coarse grid with 4 km x 4 km grid elements representing a 264 km X 240 km domain including Mount Hermon, the Dead Sea, the Golan Hei ghts, and the Mediterranean coast; and 2) a fine grid with 1 km X 1 km grid elements covering a 42 km x 50 km domain. Two three-day periods in the sum mers of 1992 and 1993, during which hydrometeorological observations were a vailable, were simulated. To account for synoptic conditions, the National Centers for Environmental Prediction-National Center for Atmospheric Resear ch mandatory-level reanalyses produced every 6 h for these periods were ass imilated by the model. The strength and timing of the various atmospheric m otions that develop in that region and their interactions significantly aff ect the hydrometeorological processes of the lake, which are subject to imp ortant diurnal and spatial variations of wind intensity and direction, temp erature, humidity, and fluxes. Since these processes have a strong feedback on the lake hydrodynamics and thermal structure, it is concluded that the development of a coupled lake-atmosphere model is needed to provide good es timates of lake evaporation when lake water surface temperatures are not av ailable. Here, it is demonstrated that RAMS performs properly, given the pa rticular complexity of the Lake Kinneret system and the uncertainty inheren t in observations above turbulent water.