Climatology of the 500-hPa mediterranean storms associated with Saudi Arabia wet season precipitation

摘要

The relationship between the Mediterranean 500-hPa storm tracks and wet season (November-April) rainfall over Saudi Arabia is investigated. The analysis is based on the application of an objective tracking scheme to the 6-hourly 500-hPa geopotential height ERA-Interim dataset (0.75A degrees A xA 0.75A degrees) for the period 1979-2012. The resulting tracks are then associated with the ERA-Interim rainfall events over Saudi Arabia. The association procedure showed that 34 % of the tracks are related to about 70 % of the rainfall. These associated tracks are used to construct climatology. A climatology of these storm tracks revealed that the eastern Mediterranean region is the preferred location for cyclogenesis with a maximum in the southwest parts of the Black Sea. The study also examined the mean radius, average intensity and average depth of the storms. The number of tracks in winter (December-February) is about 60 % of the total number which confirms the major contribution of the Mediterranean storms to rainfall over Saudi Arabia. A significant negative trend was found for storm cyclogenesis over the central Mediterranean, and the Black sea. A significant trend decrease in track density is observed over most of the northern parts of Saudi Arabia. The peaks of storm activities are observed in December and January in 1996, 1997 and 2009. Storm activity generally declines after 2000, especially in the second half of the wet season months (February-April).