Document Type : Research Paper
Shahid Beheshti University, Faculty of Earth Sciences, Department of Physical Geography, Tehran, Iran
Atmospheric Science & Meteorological Research Center, Tehran, Iran
The present study was conducted to identify the synoptic patterns that could display the origin of dust-storm over southern provinces of Iran. In order to design these patterns, we selected 17 weather stations whose data-sets of visibility per meter for one decade (2000 to 2009) were provided from Meteorological Organization of Iran. This paper used daily data of Sea Level Pressure (SLP) from NCEP/NCAR for designing the synoptic patterns as composite maps for each group. The extraction of dust records from the stations and consequently the evaluation of dust-storms frequency were our primitive aims. According to results, there were totally 345 dust-storms from 2000 to 2009 in the study area. Moreover, our results revealed that the dust-storms could be classified to three groups, including pervasive, semi-pervasive, and small ones based on Dust Stations (DS) frequency. All the dust-storms comprise 2 to 41 days. This paper illustrated the patterns for all the peak dusty days of the above-mentioned groups by extracting the sea level pressure data. According to the findings, the synoptic patterns demonstrated that the Pakistan Low is an important thermal low in Southern Asia, which pumped dust from 5 routes originated from Sahel, Southern Hijaz, and Mesopotamia Plain, toward the study area, particularly during the pervasive ones. This low appeared weak and disappeared during semi-pervasive and small dust-storms.