Modelling of a strong dust event in the complex terrain of the Dead Sea valley during the passage of a gust front

Abstract

The area of the Dead Sea valley and the adjacent regions are often affected by mineral dust. This study focuses on an extreme dust episode occurring on 22 March 2013, where near-surface dust concentrations of up to 7000 µg m−3 were encountered in the Dead Sea region. This episode is of great interest as it was accompanied by high wind speeds and a gust front that rapidly passed the Judean Mountains. Wind was even accelerated on the lee side of the Judean Mountains leading to a severe downslope wind. We simulated this situation with the comprehensive online-coupled weather forecast model COSMO-ART. Fair agreement was found between the simulated meteorological variables and the observations. The model was capable of producing a reasonable spatiotemporal distribution of near-surface dust concentration, consistent with available measurements in this area. With respect to the time of the maximum near-surface dust concentration in the Dead Sea valley, the model captured it almost perfectly compared to the observed total suspended particle (TSP) concentrations. COSMO-ART showed that the high near-surface dust concentration in the Dead Sea valley was mainly determined by local emissions. These emissions were caused by strong winds on the lee side of the Judean Mts. The model showed that an ascending airflow in the Dead Sea valley lifted dust particles, originating mainly from the upwind side of the Judean Mts., up to approximately 7 km. These dust particles contributed to the pronounced maximum in modelled dust aerosol optical depth (AOD) over the valley. Here we highlight the important point that the simulated maximum dust AOD was reached in the eastern part of the Dead Sea valley, while the maximum near-surface dust concentration was reached in the western part of the valley.