Abstract
Dust storms can suspend large quantities of sand and cause haze in the boundary layer over local and regional scales. Iraq is one of the countries that is often impacted to a large degree by the occurrences of dust storms. The time between June 29 to July 8, 2009 is considered one of the worst dust storm periods of all times and many Iraq is suffered medical problems as a result. We used data from the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS Surface Reflectance Daily L2G Global 1 km and 500 m data were utilized to calculate the Normalized Difference Dust Index (NDDI). The MYD09GA V006 product was used to monitor, map, and assess the development and spread of dust storms over the arid and semi-arid territories of Iraq. We set thresholds for NDDI to distinguish between water and/or ice cloud and ground features and dust storms. In addition; brightness temperature data (TB) from the Aqua /MODIS thermal band 31 were analyzed to distinguish sand on the land surface from atmospheric dust. We used the MODIS level 2 MYD04 deep blue 550 nm Aerosol Option Depth (AOD) data that maintains accuracy even over bright desert surfaces. We found NDDI values lower than 0.05 represent clouds and water bodies, while NDDI greater than 0.18 correspond to dust storm regions. The threshold of TB of 310.5 K was used to distinguish aerosols from the sand on the ground. Approximately 75% of the territory was covered by a dust storm in 5 July 2009 due to strong and dry northwesterly winds.
Highlights
Most of the dust storms occur in arid and semi-arid regions and they impact human health, economy, and natural resources [1]
We examined the relationship between the wind speed and direction and the Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Option
The 10 categories of TB are outlined in Figure 2a were selected based on Natural breaks (Jenks) algorithm provided by ArcGIS software [31] and are representative of different features observed in the area, i.e. water, clouds, dust, and other ground features
Summary
Most of the dust storms occur in arid and semi-arid regions and they impact human health, economy, and natural resources [1]. Dust storms are formed when strong winds blow over surfaces covered by loose and dry soil and lack vegetation coverage [3,4]. Sand and dust storms (SDS) originate over loose soil or sand and the strong winds pick up this material and causes a significant decrease in visibility. Finer dust particles are entrained in the air by suspension, which is a process that moves soil from one place and deposits it in another [5]. The propagation of dust storms (SDS) are primarily due to wind over the land surface of arid and semi-arid regions [7]. The movement of the particles through one of three modes of transport is dependent on particle size, shape and density and fine dust particles are suspended in the air and travel through the wind and are deposited hundreds or even thousands of kilometers away from their source [7]
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