شناسایی منابع تامین کننده گردوغبار غرب خوزستان با استفاده از الگوریتم‌ های بهبود یافته دمای روشنایی گردوغبار

گردوغبار را می توان یک پدیده طبیعی در نظر گرفت که در کشور ایران و به‌ویژه در استان خوزستان بروز آن در چند دهه اخیر دارای توالی بیشتری بوده است. بدین منظور در این پژوهش، شناسایی منابع تامین کننده گردوغبارهای غرب خوزستان هدف ‌گذاری گردید. بر این اساس از تصاویر ماهواره‌ای مودیس سنجده ترا برای استخراج شاخص بهبود یافته دمای روشنایی گردوغبار (badi) در سه گردوغبار متوالی در زمستان 1396 و بهار 1397 (2018) بهره برده شد. نتایج شاخص بکار رفته روشن ساخت که مناطق مختلفی در داخل و خارج کشور تامین کننده ذرات گردوغبار در غرب استان خوزستان می‌باشند. بر این اساس در اولین گردوغبار به تاریخ 2018/1/20 مشاهده شد که چشمه اصلی گردوغبار در نواحی خشک و بیابانی غربی استان در محدوده غرب شهرستان شوش و بستر خشک شده تالاب هورالعظیم در استان خوزستان می‌ باشد. در گردوغبار متوالی بعدی (2018/2/20) فرسایش در بستر تالاب هورالعظیم و مناطق بیابانی در شمال سوسنگرد را می‌توان منبع اصلی ذرات گردوغبار قلمداد کرد. همچنین می‌توان مشاهده کرد که نواحی پراکنده در کشور عراق محدوده شهر بصره نیز در این گردوغبار موثر می‌باشند. در گردوغبار سوم در تاریخ 2018/4/23 بر اساس شاخص badi دارای چندین هسته تراکمی می‌باشد و از نواحی بیابانی در کشور عربستان شروع و تا کشور کویت و نواحی جنوب غربی ایران و شرق عراق امتداد می‌یابد. همچنین در این پژوهش در محدوده‌ های فضایی استخراج شده، نقاط برداشت ذرات گردوغبار به صورت دقیق‌تر با استفاده از تصاویر ماهواره‌ ای meteosat8 و سنتینل 3 تعیین شد که بارزترین منابع داخلی در منطقه جفیر و تالاب هورالعظیم و نواحی خشک و بیابانی شهرستان شوش در قسمت غربی استان خوزستان می‌باشند. همچنین در مورد منابع خارجی بیابان‌ های کشور عربستان در مناطق غرب ریاض و شرق مدینه (الذکری، الرقایع و البجادیه) و مناطقی بین کربلا و نف در کشور عراق در شکل‌گیری توده گردوغبار نقش موثری دارند.

Identification of Desert Dust Sources in the West Khuzestan Province using of Brightness Temperature Algorithms

; Introduction ;;A dust storm is a common environmental hazards in the world, especially in arid and semiarid regions of the world. The incidence of dust has been higher in recent decades in Iran, especially in Khuzestan Province, which has become an environmental crisis in recent years. The occurrence of dust in Khuzestan Province is due to natural conditions such as successive droughts and loss of moisture sources as well as human factors such as drying of the water zones and the reduction of river water discharge due to the dam. Various methods have been developed to identify dust sources, most notably the use of remote sensing techniques. Accordingly, for the detection of dust storms, a number of dust indices have been developed based on MODIS images, the most effective of which is the use of the BADI. Therefore, in this study, three consecutive dusts in winter and spring of 2018 in Khuzestan Province were studied through the BADI.;; Study area;;The study area includes the lands west of Khuzestan Province between north latitudes of 32°8 apos;.62 to 30°57 apos;.26 and east longitudes of 47°43 apos;.21 to 48°32 apos;.29 . In terms of political divisions, this area has two cities, shush city in the north, and the Dasht Azadegan is in the south, which has a common border with Iraq. Karkheh River is the most important river in the area which is flowing through Khuzestan plain to Hoor AlAzim Wetland.;; Material and Methods;;In this study, the BADI index was used for desert dust detection. First, to use this index, Modis 1B satellite images were obtained from the NOAA Archive (https:// ladsweb. modaps. eosdis.nasa.gov/search/).;Subsequently, geometric corrections were made to them and using calibrated images, the brightness temperatures were calculated in bands 20, 31 and 32 of Modis images. Also, Meteosat 8 satellite images were used to specify the dust source regions. In addition, Sentinel 3 satellite images were overlaid with Google Earth satellite images to determine the exact locations of dust particles.;; Results and Discussion ;;BADI Algorithm;According to BADI index extraction, in the dust of 20/1/2018 it was observed that the main source of dust is in the western part of Shush City and the dry bed of Huralazim wetland in Khuzestan Province. These conditions cause severe dusting due to local topography (flat area and nonvegetation lands). In addition, conditions for dust formation have been provided due to development plans and the elimination of local morphology as well as the loss of soil moisture (land drainage) in the south and west of Khuzestan Province. In the next dust storm that occurred about a month later in the winter (20/2/2018), the results show that erosion in the Hoor AlAzim Wetland and the desert areas in the north of Susangerd can be considered as the main source of dust particles. Therefore, the amount of soil erosion after dust based on field operations and the measurement of fixed rod height indicates approximately one centimeter of height difference between the two successive dusts. In the third dust on 23/4/2018, a very large dust with high mass, several density cores were seen which would begin in the desert regions of Saudi Arabia and extend to Kuwait and Southwestern Iran and also Eastern Iraq.;Determining the sources of dust;Meteosat 8 satellite images were used at different times of the day to identify the high dust areas. The spatial area of dust particle loading was determined from the beginning to the time of the dust mass expansion. In the dust on 20/1/2018, first the inner sources of the Dust were activated due to the cyclonic motion of the air mass. In the dust of 19/2/2018, it can be stated that the soil erosion of the Hoor AlAzim bed and the surrounding areas such as Gofer and arid lands of southern Bostan are the main cause of this phenomenon. In the next dust on 23/4/2018 the main sources of dust are the deserts of Saudi Arabia (Kuwait and Saudi Arabia) and the deserts of Northern Najaf and Southern Karbala in Iraq. Then, Sentinel 3 satellite images were used to determine more precisely the dust loading points in the study areas. Therefore, the results illustrated had a significant role in increasing the volume and concentration of dust in winter the eastern areas of Hoor AlAzim (Gofer and Southwest Bostan) and the western deserts of Shush. Also, based on the detection of dust dumping sites, the results indicated that three areas in the west of Riyadh and east of Medina (AlDhakari, AlRaqqa and AlBujadiyah) play an important role in the formation of the dust mass.;; Conclusion;;The purpose of this study was to monitor the dust and extract dust sources of West Khuzestan using the BADI index. Accordingly, in the three dusts investigated in winter and spring of the 2018, different areas within and outside the country supply dust particles in the west of Khuzestan Province. However, it is important to note that internal sources of dust due to proximity to cities and villages in Western Khuzestan are capable of creating dust storms with a radius of less than 1000 m, which makes them more vulnerable.