Semi Operational Prediction of the Dead Sea Evaporation—A Synoptic Systems Approach

Abstract

The predictability of pan evaporation and air temperature in the southern part of the Dead-Sea region (Sdom) was investigated according to two approaches, prediction by mesoscale models and with the aid of synoptic classification. First, the predicted temperature, wind speed and relative humidity that directly affect the evaporation are obtained from the WRF mesoscale model predictions. Predictions according to multilinear regression equations and a Penman-Monteith approach were also validated against observations in Sdom. The WRF model predicts the temperature reasonably well. However, the wind speed and relative humidity predictions were found to be very poor. The unique approach in this paper is employing a semi-objective synoptic systems classification according to the global GFS model. Relationships were defined between the 19 Eastern Mediterranean’s (EM) synoptic systems and the Sdom evaporation, temperature, wind speed and relative humidity. A monthly evaluation was performed for each of the systems and the semi-objective prediction was verified by the semi-objective classification. Since some synoptic systems affect the evaporation and temperature similarly, the 19 synoptic systems were grouped into seven clusters, each containing systems with similar evaporation and temperature records. This method has yielded a significant improvement in the daily prediction of evaporation and temperature. Semi-objective definitions for the synoptic systems were performed for the ranges of 12 - 132 hours. The synoptic system approach succeeded in the prediction of the evaporation and temperature changes in Sdom for a few days in advance. The predictability skill for the 12 hour forecast achieved about 80% of success, dropping to 70% at 36 hours. For 60 to 132 hours the prediction stabilized at a skill of 60%.The method presented here is a new attempt to predict meteorological parameters by using a synoptic classification approach in the Dead-Sea area where even high-resolution mesoscale modeling forecasts are not very successful.