Assouline, S., Watershed Unit, Jordan District, Mekorot, Tiberias, Israel
Mahrer, Y., Seagram Ctr. for Soil and Water Sci., Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel, Seagram Ctr. for Soil and Water Sci., Faculty of Agriculture, Hebrew University of Jerusalem, P.O. Box 2, Rehovot 76100, Israel

Microclimate characteristics and latent and sensible heat fluxes were measured continuously and simultaneously over Lake Kinneret, Israel, during two consecutive summers at the eastern (Ein Gev) and western shores (Sapir) of the lake. The data were used to characterize the variability in basic meteorological variables (air temperature and humidity, water surface temperature, and wind velocity) and in evaporation rates. Analysis of the data on an hourly basis reveals the combined effect of local physical processes occurring during airflow over water surfaces and the diurnal regional phenomena of the inland penetration of the Mediterranean sea breeze downslope into the area during the afternoon hours. The resulting strong, hot and dry westerly winds at the western coast become weaker, cooler, and more humid as they reach the eastern shore after a delay of 1-2 h. Consequently, the maximum evaporation rate at Sapir was occasionally twice the corresponding rate at Ein Gev. The data on a daily basis depicted the influence of synoptic systems on the regional climate. Commonly, the mean evaporation rate from the entire lake is assumed to be equal to that evaluated at a specific site. Considering the observed variability, this assumption might lead to errors as large as 100% on the daily basis and of 15% on the seasonal basis.