نوع مقاله : مقاله پژوهشی
نویسندگان
1 کرج، حسین آباد - راه آهن(پشت مترو کرج)- بلوار آخوندی ها، کوچه شهید احمدی، (کوچه مسجد) پلاک 9 واحد 4
2 منوچهر فرج‌زاده، استاد آب‌و‌هواشناسی، گروه جغرافیا، دانشگاه تربیت مدرس، تهران، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
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.
The study of the impact of atmospheric dust corridors on Iran showed that a significant percentage of the dust corridors that occurred in the entire studied area (58%) affected Iran. From March to September (maximum in summer), at least 60% of Iran's area is affected by corridors at least once. In general, the geographical distribution of the density of occurrence of corridors has an inverse relationship with the height above sea level. The highest frequency was observed in the southwest of the country and in Khuzestan province. According to the wind pattern and the geographical location of the dust centers, most of the dust corridors enter Iran from the west and south. In general, by providing a comprehensive understanding of dust transport patterns in the Middle East and North Africa and investigating its effects on Iran's climate, this research provides a suitable platform for future research and highlights the importance of investigating dust atmospheric corridors in climate planning, public health and sustainable development.
کلیدواژه‌ها [English]
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