Spring Saharan Cyclones over Saudi Arabia: Preliminary Study of the Impacts on Climate

Abstract

Saharan cyclones are an important feature of the seasonal spring climate of Saudi Arabia. It was found in an objectively tracking scheme that of 688 Sahara tracks, 53 of them reached Saudi Arabia during the period 1958–2018. Two distinct regions of cyclogenesis are identified: the first is Area A (Algeria, in particular, south of the Atlas Mountains) and the second is Area B (Libya and Egypt). The 53 tracks that pass or abate over Saudi Arabia are ultimately categorized into five key routes. The Saharan cyclones intensify near or over the Mediterranean, develo** a relatively strong pressure gradient during their lifetimes which weakens as they pass over the Arabian Peninsula. Cyclones develop usually under a tropical trough over North Africa, which is accompanied by a thermal ridge with a very strong temperature gradient. This pattern is also found at upper levels of the atmosphere. During the cyclones’ movement over Saudi Arabia, they extend upwards, and at higher levels, pressure levels of up to 500 hPa can be observed. The study also revealed that more tracks occur during the negative phase of the North Atlantic Oscillation, reflecting the role played by subtropical high pressure in controlling the movement of the Saharan cyclones. Cyclones originating over Area B are more frequent in recent decades than in the earlier decades. Cyclones originating in Area B are found to have more influence on the climate of Saudi Arabia than those occurring in Area A. Saharan cyclones that reach Saudi Arabia substantially increase the frequency of dust storms, raise the minimum temperature and maximum wind speed, and cause a reduction in minimum visibility. These results suggest how they may contribute to weather forecasts for the region.