Intraction between East Khorasan Winds Regimes and Sistan 120 Days Winds

The main goal of this study is to investigate theinteractionbetween East Khorasan winds regimesand Sistan120 Days winds. The climatic data of Synoptic stations used in the present study was obtained fromkhorasan razavi, khorasan jonobi and sistan and baluchestan meteorological organizations. The statistical period is from 2000 to 2011. To do synoptic analyses, the maps of sea level pressure, geopotential height of 850 Hectopascal level, wind direction and the relativevorticity were used. The sample extract form the daily wind velocity data base of Zabol station and include the fourteen days with the highest velocitywinds.
The results shows that the wind direction in the Khorasan Razavi province is from north. while, the direction changes toward Northwest as it arrives to Sistan plain. This change in the direction of wind is due tothe topographyand geographical location of thearea. The geopotential height maps shown that the main reasons for the winds of 120 days are thecore ofthe highpressureonthe Caspian Sea and the core of the low pressure in Pakistan. Moreover, strengthening the low pressure intensifies the winds