The present work focuses on examining dryness of Hamoun lakes, synoptic and dynamic meteorological conditions associated with dust-storm outbreaks during the summer (June-September) months of the period 2001 - 2012 over south west Asia. Moreover seasonality, dust-plume altitudinal variation and affected areas for dust storms over the area were examined via the satellite observations (TOMS, OMI, METEOSAT, MODIS) and HYSPLIT trajectories. Monthly-mean composite maps of TOMS and OMI AI show high (>3-3.5) values over Sistan basin(border Iran, Afghanistan) and nearby downwind areas, while statistical analysis reveals that the Sistan dust storms are not teleconnected with dust storms over Iraqi plains and Arabian Peninsula suggesting differences in the meteorological field controlling them. Satellite (Landsat) and meteorological observations reveal that the water levels in the Hamoun lakes exhibit considerable inter-annual variability. This is the trigger for concurrent changes in the frequency of the dusty days, aerosol loading and deterioration of visibility over the region, as satellite (TOMS, MODIS, MISR) observations reveal.RegCM4 model simulations reveal that the intense northern Levar wind, the high surface heating and the valley-like characteristics of the region strongly affect the meteorological dynamics and the formation of a low-level jet that are strongly linked with dust exposures. The intra-annual evolution of the dust storms does not seem to be significantly associated with El-Nino Southern Oscillation, despite the fact that most of the dust-storms are related to positive values of Oceanic Nino Index. In contrast, the dust-storms are found to be linked with dryness of the Sistan Basin, higher wind speed and lower relative humidity. NCEP/NCAR reanalysis reveals that the dust storms are associated with low sea-level pressure conditions over the whole south Asia, while at 700 hPa level a trough of low geopotential heights over India along with a ridge over Arabia and central Iran is the common scenario. A significant finding is that the dust storms over Sistan are found to be associated with a pronounced increase of the anticyclone over the Caspian Sea, enhancing the west-to-east pressure gradient and, therefore, the blowing of Levar. The Infrared Difference Dust Index (IDDI) images, which represent brightness temperature reduction due to dust presence over land, are used at specific periods of persistent dust storms over Sistan confirming the main pathways of the dust plumes and illustrating the importance of the region as one of the most active dust sources in southwest Asia. Analysis of the HYSPLIT forward 5-day trajectories originating from Sistan reveals the favorable dust-plume pathways and the dust-affected areas over southwest Asia.

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