Investigation impact of massive dust storm on aerosol optical, physical, radiative properties over Southwest Iran

In this paper, a variety of satellite data and ground measurements were used to provide a comprehensive analysis of the characteristics of two powerful dust storms that occurred over the southwestern parts of Iran in mid-March 2012 (first ~11-14 March and second ~15-18 March). In order to better understand the effects of this kind of dust storm on aerosol optical and radiative properties different types of data were used during study days. The purpose of this study is an attempt to understand and analyze the effects of this kind of dust storm on aerosol optical and radiative properties, and their source's origins using different types of data such as satellite observations, ground measurements, and model output. The analysis of dust aerosol characteristics based on the meteorological data collected in the city of Ahvaz, measurements of the closest AERONET site at Kuwait University, and satellite data from Moderate Resolution Imaging Spectroradiometer (MODIS), Ozone Monitoring Instrument (OMI), and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) showed significant changes during dusty days compared to non-dusty days. During the two storms, horizontal visibility, temperature, and humidity of the area decreased significantly, reaching as low as 300 m, 12°C, and 23% on the day with the highest aerosol pollution (March 18). Also, during the dust storms, the AERONET aerosol optical depth (AOD) observations at the Kuwait University and the measured PM10 concentration in Ahvaz meteorological station increased by respectively 4.5 and 9 times, reaching as high as 2.7 and 2600 µg/m³ on March 18. The high values of MODIS AOD and OMI aerosol index clearly showed the spatial growth of the storms, which affected the study area as well as many other countries around the Persian Gulf. The CALIPSO vertical profile of total attenuated backscatter at 532 nm showed the vertical expansion of the storm to an altitude of 6 km which confirms the high aerosol loading over the study region. The ARF values ranged between -63 to -16 w/m² (average: -39 w/m²) at the top of the atmosphere, and between -202 to -83 w/m² (average: -132 w/m²) at the bottom of the atmosphere. Such conditions can result in cooling at the surface and warming in the atmosphere. In addition, the results of the DREAM simulation showed good agreement with the retrievals from satellite observations, and also the analyses of the HYSPLIT model.