Synoptic analysis of Saudi pressure and effect on drought the South and South West of Iran

The present study aims at synoptic analysis of Saudi high and its effect on the drought of southern and southwest of Iran. Located in the south and southwest of Iran, the precipitation data of 28 synoptic stations during a 10-year statistical period (2000- 2009) are gathered from the Iran Meteorological Organization. Using the Standardized Precipitation Index (SPI), the drought period of the region was extracted, in which 2008 was considered as the driest year. Moreover, synoptic maps were determined and analyzed in 4 levels, called sea level pressure, height, and Omega at 850, 700 and 500 HP during January, February, March, April, November and December. The central closed contour of the precipitation in 6 months of 2008 on a daily basis at various levels revealed that geopotential height contour is closed at 850 hPa, 700 hPa, and 500 hPa as 0.77, 0.98 and 0.99 respectively. Besides, the central closed contour in 2001 during the 6 humid months showed daily that the geopotential height contours are closed at the level of 850 hp in 0.68, 700 hp in 0.83 and 500 hp in 0.77. Since there was a severe drought during 2008, it is revealed that more contour of center anticyclone is closed. Furthermore, centered anticyclone over land was as east-west in 2008 and 2001 which is more common in the combination of north of Africa and the anticyclone of Saudi Arabia. In addition, the ridge has been locating on Iran and Saudi Arabia in recent years dominating the stability in the area. Therefore, Mediterranean trough cannot penetrate lower latitudes moving to higher ones. In conclusion, the southern half of Iran is not affected by precipitation systems. However, the low pressure of Sudan has been progressing on the Red Sea and not penetrating in the study area.