Dynamics of a severe summer Shamal wind and its induced dust storm in the Middle East: A diagnostic study based on numerical simulation

Abstract

This study investigates the formation and dynamics of the Summer Shamal Wind (SSW) and its associated dust storms over the Middle East. A regional climate model, RegCM4, coupled with a dust module, is employed to simulate a severe dust storm event on June 12, 2006. To gain deeper insights, a novel dynamical mechanism is proposed. This mechanism highlights the crucial role of both mechanical and thermal forcing in shaping the regional atmospheric circulation. The vertical heat advection from the Zagros Mountains (ZAG), combined with the mechanical forcing from a shallow incident flow originating from the Turkmenistan anticyclone, triggers upward motion over the ZAG. This synergistic effect leads to the development of a mid-tropospheric anticyclone over the ZAG, which, in turn, induces a westward-propagating Rossby wave. The downward motion and descending air associated with this wave over Mesopotamia establish a terrain-induced local circulation. Consequently, the SSW emerges within a shallow layer at the null-vorticity zone of a coupling-pressure pattern formed by the Arabian anticyclone and the Zagros trough, which is itself a product of the terrain-induced circulation. The study concludes that the intensification and southward movement of the Turkmenistan anticyclone play a pivotal role in the formation of severe SSWs and subsequent dust storms over the Middle East.