عنوان مقاله [English]
A mean diagnostics analysis for a period of one year (July 2001-July 2002) of Mediterranean cyclones and their impacts on the Middle East weather is carried out. The diagnostic tools used in this study are the monthly mean geopotential height and relative vorticity at 850 and 500 hPa as well as the monthly mean 1000-850 hPa thickness. In addition, using an objective method about 30 cyclones were identified that occurred in the Mediterranean region during the period of one year. The characteristics of each cyclone, such as duration, intensity, path, source region and its dynamic were examined. The results show that the strength and the number of cyclones in the whole Mediterranean region are significantly decreased during the period of early June until the end of September, largely due to the movement of the subtropical high to the higher latitudes. Also, the Persian Gulf pressure trough, which is an extension of the southwest Asia monsoon, acts to weaken the intensity of cyclones and slow down their eastward movement in the eastern Mediterranean region. During early October until the end of January, as the effect of subtropical high is weaken in the northern Mediterranean, cyclogenesis activity increases over the Aegean Sea and the Gulf of Genoa. Since these cyclones move northwards, their effects are rather weak in the Middle East weather. From February to May, the cyclonic occurrences in the northern Africa increase, mainly due to the strong temperature gradient between the North Africa coast and the southern Mediterranean. As these cyclones move over the Saudi Arabia and the Red Sea, the Middle East weather is affected.