Synoptic characteristics of spring dust days over northern Saudi Arabia

Abstract

This study describes the synoptic features associated with spring dust cases over northern Saudi Arabia. Dust cases were detected and classified using the values and distribution of the aerosol index (AI) from the total ozone mapping spectrometer (TOMS) satellites. The classes were narrow spread, moderate spread, and wide spread. In addition, the dust types observed at the surface weather stations during the detected cases were used to describe the distributions of various dust types over northern Saudi Arabia. The results demonstrate that the eastern side of the region experiences considerably more dust storms than non-dust-storm types (haze, etc.), whereas the western side near the Red Sea is only influenced by a limited number of dust-type observations. Moreover, a synoptic analysis of the classes shows that increases in the class strength produce a synoptic feature in which the pressure decreases within the western high-pressure ridge and eastern low-pressure system; as a result, the low-pressure trough that typically affects the northern Arabian Peninsula extends northward. Additionally, the maximum winds at 250 hPa decrease and shift northward, the stability and instability between 1000 and 850 hPa increase, and the stability between 850 and 500 hPa decreases. At 500 hPa, the northern cyclone weakens, and the southern anticyclone strengthens. As a result, the northern trough weakens, the ridge shifts northward, and the geopotential height gradient and wind velocities decrease. In general, these features represent the atmospheric conditions that increase the severity of dust cases over this region.