The study of a rare frontal dust storm with snow and rain fall: Model results and ground measurements

Abstract: Dust plays an important role in the modification of microphysical and optical properties of clouds. The presence of dust at an elevated level significantly increases snow mass and rain concentration. A rare phenomenon of rain and snowfall with dust was occurred simultaneously in the eastern Iraq, Syria, and west and south west of Iran on 19 and 20 January 2018. In the meantime, while the dust impact was dominating over a large area within Syria, Iraq, Saudi-Arabia, Kuwait and Iran, it consequently caused extreme temperature drop, rain and snowfall problems for the residents living in the Middle East. Likewise, a visibility drop together with rainfall was also observed in the same region. The visibility was reduced to less than 500 m over most of the region. Further, an image showing dust mass taken from the satellite with higher amount of AOD (≥1) indicated the severe dust activity. It is worth to mention that a dynamic low pressure system covering the surface, and also the cold and warm fronts and the relevant occluded front caused such a phenomenal problem. The dust storm on 19th January was mainly prefrontal typed and transported from Horolazim Lagoon, Ad Dahna and An Nafud deserts, under the impact of the south easterly winds. The cold front was displaced to the eastward with a consequent dust storm on 20th January, originated from the vaster parts in Iraqian and Syrian deserts and Ad Dahna and An Nafud deserts. The back trajectory analysis of HYSPLIT MODEL shows the different sources of dust in the study region during 19-20th January. On the whole, it can be concluded that the dust concentration and atmospheric quantities, including the wind, the precipitation, and the cold and warm fronts having a permissible effect on simulation processes, are well simulated by the WRF Chem model. The comparison of WRF-Chem and NAAPS outputs revealed that the dust pattern and the procedure of vertical transfer of particles of each model are very identical, but the amounts of dust in the Model NAAPS are underestimated.