Synoptic Analysis of Dust in the North East of Iran

An identity of dust atmospheric patterns and extreme dust in northeastern Iran is the aim of the study. This main was determined to using of daily visibility data in ten synoptic stations from its establishment until 2009 and digital data of geopotential height and wind components from NCEP- NCAR and to principle component analysis and clustering approach. In northeastern of Iran, respectively, the dust of cold half is related to western Asia trough, Iran eastern trough and low in the region to central Asia, whereas the cause of warm half dust is subtropical high, Iran-Pakistan low and Caspian high with maximum pressure gradient in the region. This condition intensified to 5900 meters of subtropical height in the region. In the cold half, Cutoff low in north and northwest of Caspian along strong low caused extreme dust and extreme dust of warm half is related to the establishment of blocking and cutoff low of Western Asia, Pakistan low and Caspian high. Thus, extreme dust, other similar climatic events is related to the cutoff low and blocking neighbor to Iran. According to the position of the atmospheric patterns above-mentioned, throughout the year, central Asia desert and eastern of the region to north and northeast flow, is a source of dust in warm half and dust course of cold half related to the position of fronts of the cyclone and unstable weather, are internal deserts.