Modeling of Foehn-Induced Extreme Local Dust Pollution in the Dead Sea Valley

Abstract

Using high-resolution COSMO-ART model simulations, a foehn phenomenon and foehn-induced effects on extreme local dust pollution on 22 March 2013 were analyzed over the Judean Mountains (~1000 m) and over the Dead Sea valley (−420 m). The model data were supplemented with in situ meteorological measurements from a chain of stations located across the mountain ridge. Hot foehn winds created a pronounced temperature inversion over the western part of the valley. Strong foehn winds activated local dust sources, while the foehn-induced pronounced temperature inversion trapped dust particles beneath the inversion. These trapped local dust particles contributed to maximum surface dust concentration but not to dust aerosol optical depth (AOD) in the western Dead Sea valley. By contrast, in the central and eastern Dead Sea valley, in the absence of temperature inversion, the ascending airflow lifted dust particles up to 2-km altitude, contributing to the maximum local dust AOD. Thus, it was because of the temperature inversion in the western Dead Sea valley that the maximum surface dust concentration did not coincide with the maximum AOD. This lack of coincidence indicates difficulties in using satellite-based AOD for initializing dust concentration within numerical forecast systems over a region with complex mountain terrain.