Climatology of atmospheric dust corridors in the Middle East based on satellite data

Abstract

Dust aerosols can sometimes extend thousands of kilometers continuously in the atmosphere. In this study, we refer to these dust streams, as Atmospheric Dust Corridors (ADCs). This study aims to identify ADCs by an automated algorithm and investigate their temporal and spatial characteristics in the Middle East. In order to do this, the Aerosol Optical Depth (AOD) and Angstrom Exponent (AE) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) (Aqua) were obtained on a daily scale at a resolution of 1*1° between 2003 and 2020. In this study, observations with AOD above 0.3 and AE below 0.75 were considered as dust aerosols. After determining a set of conditions, an algorithm was developed to identify the ADCs automatically. In the first step, the dust masses were identified using the connected components labeling method, and the largest dust mass was selected from each day. Then, a set of conditions were examined such as geometric shape and motion of the dust mass (based on wind data). As a result, we identified 281 ADCs and classified them according to their direction of movement. We found 33% cases of ADCs that flow toward the west, 19% cases that flow toward the east, 36% cases that flow toward the south, and 12% cases that flow toward the north. All the directions had the highest frequency in September, April, and March, whereas February, November and December had the lowest frequency. Spatially, the highest frequency can be seen around 45°E over Saudi Arabia, Iraq, and Syria. Western and southern ADCs are primarily found in the Arabian Peninsula and in Iraq, Syria, southern Iran, southern Afghanistan, and northern Pakistan, while northern and eastern ADCs are primarily found in northern Africa (Sudan and Chad, Niger, and Libya). May is important for western ADCs, September for southern ADCs, and April for eastern and northern ADCs. According to the Mann-Kendal test, no significant trends were observed on a monthly or annual basis during the studied period.