A Study of Pressure Gradient during the Activity of 120-Day Winds of Sistan and its Relationship with Dust and Wind Speed in Helmand Basin, Iran

120-day wind of Sistan is a regional wind current that blows on average from June to September. This wind, which is accompanied by dust, has carved its role on the face of the Sistan region due to its continuity and speed. This study aimed to investigate the pressure gradient during the activity of 120-day winds and its relationship with dust  and wind speed in Helmand Endorheic basin. For this purpose, the dust and wind speed data of 11 synoptic stations were daily extracted from the Iran Meteorological Organization since 1986 for Helmand basin. After making a complete database, the frequency of dusty days and wind speed during the activity of 120-day winds of Sistan was extracted. Atmospheric pressure data corresponding to the duration of the activity of 120-day winds was extracted from the National Center of Environmental Prediction (NCEP) and National Center of Atmospheric Research (NCAR) databases with a spatial resolution of 2.5° × 2.5°. Following the extraction of pressure gradient via Pearson correlation coefficient, the relationship between the speed and dust of the basin, and the pressure gradient was investigated. The study of wind speed showed that strong winds during the activity of 120-day winds had an increasing trend. The results also revealed that the pressure gradient had a direct relationship with wind speed and dust storms in Helmand basin. In addition, the speed and dusts of the mid-eastern part of the basin were mostly influenced by the pressure gradient.