Dynamical Transportation of Aerosols for Extreme Dust Storms Over Al-Jazira Region

Abstract

The characteristics and classifications of aerosol properties over Iraq was studied in this paper. The 1°×1° grid of monthly aerosol optical depth and angstrom exponent data of the period 2005 to 2017 in Iraq is used from Terra of MODIS. Moreover, the 1°×1° grid of Aerosol Index is used and it is available from NASA's Data and Information Services Center for Earth Sciences (GESDISC). The backtrjectory for 12 dust extreme events over the Al-Jaziraregion was studied by using the Single-Particle Lagrangian Integrated Trajectory model (HySplit-4). The spatial-seasonal aerosol properties over Iraq were obtained from EOS-Aura satellite by Ozone Monitoring Instrument. The high-high clusters of aerosol optical depth and Aerosol Index values which refer to high concentration have been found in western and southern Iraq however low-low clusters have been found in the winter season over the whole of Iraq. According to Angstrom Exponent, there are three kinds of aerosol modes: fine, mixture, and coarse. This classification shows the maximum area under fine aerosols mode has occurred in the winter with 13.6% whereas the spring season did not show any area with fine aerosols mode. Moreover, the coarse mode covers the maximum area during the summer season with 97.7% and the minimum area during the winter season with 77. 2%. To demonstrate the relationship between topography and aerosol characteristics, Aerosol Properties Index is used which shows the degree of aerosol coarseness in each pixel. Using Geographically Weighted Regression and Ordinary Least Squares, the Aerosol Properties Index geographical distribution is strongly influenced by topographic conditions. Where the maximum coefficient of determination has been observed in the spring (R2=0.91) from the Geographically Weighted Regression model, while Ordinary Least Squares shows a lower coefficient of determination (R2=0.33), Geographically Weighted Regression in comparison to Ordinary Least Squares shows a better coefficient of determination in all seasons. The back trajectory for extreme dust events shows that some sources of air masses and their path to the study area through two pressure levels (1000 mb, 850 mb) and the geographical desert in the area of the study are the main cause of dust storms in the study area.