The synoptic patterns of widespread dust days in the northern Arabian Peninsula in summer

Using an aerosol index (AI) threshold for the TOMS satellite, dust episodes were detected and classified. The selected cases show that approximately 82% of the summer is dusty, while 9.3% of the summer experiences widespread dust episodes. A statistical analysis of widespread dust episodes in summer demonstrated that there are four main synoptic patterns, which represent 52% of the cases over the northern Arabian Peninsula. In addition, a synoptic analysis of these main patterns shows that two factors control these cases: the scale of the pressure systems in the region and the interaction between the Azores high and Indian low pressure systems. The frequency of a synoptic pattern is inversely proportional to the scale of the influence of the synoptic features over the Arabian Peninsula. Furthermore, a frequent pattern appeared when the Azores high pressure system was strong and dominant, while a less frequent pattern appeared when the Indian low pressure was strong and dominant and when a high-pressure belt was present over the northern region. Moreover, two moderate patterns whose frequency depended on the synoptic similarity to one of the extreme patterns occurred.