Analysis of spatio-temporal dust aerosol frequency over Iran based on satellite data

Iran is located in the dust-belt region and so dust is a main environmental issue over the country. The main purpose of this study is to better understand of the spatial and temporal properties of the Dust Aerosol Frequency (DAF) over Iran using satellite data. Daily Moderate Resolution Imaging Spectroradiometer (MODIS) deep blue Aerosol Optical Depth (AOD), Angstrom Exponent (AE) (both Terra and Aqua, Level 3, Collection 6.1) and Ozone Monitoring Instrument (OMI) Absorption Aerosol Index (AAI) were obtained at 1 degrees x 1 degrees spatial resolution over Iran for the 10 years from 2006 to 2015. In this study observations with AOD higher than 0.3, AE < 0.75 and AAI > 0.7 are considered to be dust aerosols. Results showed that the maximum areas with high DAF are located in the Khuzestan province in the southwest and Sistan in the east of the country. The other areas with peak DAF were observed in the low elevation areas of the country, namely coastal plain of the Oman Sea, Jaz Murian depression and Lut desert in the southeast, and Southern Dasht-e Kavir in central northern. DAF is decreased significantly at latitudes higher than 34.5 degrees N. The maximum and minimum DAFs over Iran occur in July (Terra = 2.02, Aqua = 2.1) and November (Terra = 0.1, Aqua = 0.05), respectively. We found good spatial relationship between DAF with the meteorological codes frequency related to the dust from weather stations as well as with the fraction of dust AOD and from Monitoring Atmospheric Composition and Climate (MACC) project. In addition, results showed that dust frequencies based on both weather station and satellite data exhibited corresponding relationships with latitude, elevation, vegetation cover, precipitation and temperature.