Seasonal and diurnal evaporation from a deep hypersaline lake: The Dead Sea as a case study

Abstract

Evaporation plays a major role in lake systems, as it affects the water, energy and solutes budgets. Water salinity reduces evaporation, and as a result affects the energy budget of the lake, including stored heat. In this study, we explore the seasonal and diurnal variations of evaporation and other energy fluxes over the Dead Sea, the deepest and saltiest hypersaline lake on Earth. We present two consecutive years observations using Eddy Covariance system, meteorological stations and a buoy station measuring the water column properties. These observations reveal the effects of synoptic and mesoscale atmospheric circulation on lake evaporation. The seasonal cycle of evaporation is characterized by two peaks. The summer evaporation peak is related to high radiation inputs. The winter peak stem from the high heat storage of the deep lake, with evaporation driven by high vapor pressure demand, combined with synoptic scale wind systems and thermal instability. In summer, the synoptic circulation is stable, providing a weak background wind velocity (Persian trough), hence, the dominant diurnal wind pattern is induced by the Mediterranean Sea Breeze (mesoscale circulation). The two years of eddy covariance measurements in the hypersaline Dead Sea, located in a hyperarid region, revealed annual evaporation rate of 1.13 ± 0.13 m yr−1. We explored several evaporation models versus the directly measured evaporation, and found that the most reliable is a mass transfer model, that was calibrated here for the Dead Sea.