آشکارسازی تاثیرگذاری رخدادهای گردوغبار فراگیر در مقادیر شار تابش خالص موج کوتاه ورودی سطح زمین (مطالعه موردی استان خوزستان)

در این مطالعه سعی شد که تاثیرگذاری رخداد گردوغبار در زمینه نوسانات و تغییرات روزانه میزان تابش خالص موج کوتاه دریافتی در سطح زمین استان خوزستان مورد بررسی قرار گیرد. در این راستا داده های روزانه 6 ایستگاه سینوپتیک و کدهای گردوغباری و سرعت و جهت باد توام با آن ها استخراج گردید. با استفاده از داده های ایستگاهی 3 کیس گردوغبار فراگیر در سطح استان خوزستان و در ادامه با استفاده از دو شاخص گردوغباری محصول سنجنده modis یعنی شاخص انگستروم هواویزه ها (aea) و شاخص عمق اپتیکال هواویزه ها (aod) وضعیت توزیع فضایی گردوغبار در سطح استان بررسی شد و با استفاده از داده های باز تحلیل شده تابش خالص موج کوتاه دریافتی (در ساعت 12 ظهر یا 09 utc) پایگاه ecmwf ، تغییرات زمانی و مکانی میزان تابش دریافتی بررسی شد. نتایج حاصل از بررسی 3 کیس گردوغبار فراگیر در سطح استان (شامل 19  ژوئن 2012، 12 می 2018 و 22 جولای 2010) بیانگر آن بود که، ذرات آیروسل عموماً در بخش های مرکزی، جنوبی و غربی استان (نواحی دشتی و پست استان) از نوع ذرات با اندازه متوسط (شاخص نمایی انگستروم بین 0/5 تا 1) و در بخش های شرقی و شمال شرقی، از نوع ذرات درشت ( شاخص انگستروم کمتر از 0/5) بوده است. نتایج حاصل از تاثیرگذاری رخدادهای گردوغبار بر میزان تابش موج کوتاه دریافتی سطح زمین نشان داد که در رخداد گردوغباری 22 جولای 2010 شاخص نمایی انگستروم بیانگر حضور ذرات درشت در اتمسفر نزدیک سطح زمین و شاخص aod نیز بیانگر حضور گردوغبار غلیظ در کل پهنه استان بوده است، میزان تابش خالص موج کوتاه دریافتی (در ساعت 12 ظهر یا 09 utc) حدود 194 وات بر متر مربع ( حدود28 درصد) کمتر از میانگین همان ماه بوده است. این میزان افت در دو موج گردوغبار دیگر که مقادیر شاخص aod  و شاخص انگستروم آن ها بیانگر گردوغبار ریزتر و با غلظت کمتر بود، کمتر بوده است. در موج گردوغباری 19 ژوئن 2012، میزان تابش خالص موج کوتاه دریافتی تنها 5 درصد ( 25 وات بر متر مربع در ساعت 12 ظهر یا 09 utc) کمتر از میانگین بلندمدت بوده است و این افت در رخداد گردوغباری 12 می 2018 برابر 28 وات بر متر مربع (حدود 4 درصد افت نسبت به میانگین همان ماه) بوده است.

revealing the effect of pervasive dust events on the net shortwave radiation flux values entering the earth's surface (case study of khuzestan province)

introductionextensive and massive agriculture, along with other agricultural activities such as animal husbandry, industrial activities in the southern half of the province, has created and intensified extensive changes in the environmental resources and natural structure of the province. this extensive change can show its effects and consequences in the destruction of forest lands, the transformation of rich pastures into poor pastures and barren lands, severe soil erosion, and finally the creation and development of internal centers of dust. and intensify the severity of dust incidents in the province. dust events have profound and significant effects on agriculture and soil fertility, health and hygiene, disruption and destruction of industries and power plants, and negative effects on the environment, including the deterioration of forests. airborne particles, which are mainly driven to the region by dust storms, are one of the important components of the atmospheric system. they can not only change the albedo of the energy balance by acting as cloud particle nuclei, or ice nuclei.materials and methodsthe study location of this research is khuzestan province, which is one of the most challenging provinces in the country in terms of environmental hazards. this province, with an area of about 6.5 million hectares, occupies about 4% of the country’s area. dust is one of the major and most important challenges of this province. its destructive effects can be traced in various dimensions, such as the quality of water resources, the quality and performance of agricultural products, industries and energy transmission networks, and the air quality of cities. three categories of data have been used in this research. the data of the first category is related to the data of widespread dust days in khuzestan province. these data were obtained from the dust codes of the current air condition (ww parameter of synoptic stations of the province) during the statistical period of 2000, 2020. the second category of data was actually the remote sensing data of modis sensor, which included the aerosol optical depth (aod) product of modis sensor (mod04 product) and aerosol exponential index (aea). these two indicators are dimensionless but with different directions. in the aod index, higher numbers represent more aerosols in the atmosphere and in the aea index, in addition to the presence of dust in the place, it also provides the size of the aerosol particles. finally, the third category of data is the reanalysis data related to incoming net shortwave radiation (snsr), which was taken from the reanalysis data of the european ecmwf database version era5 with a spatial resolution of 0.5 arc degrees.  conclusionin this research, it was tried to investigate the influence of the dust event in the context of fluctuations and daily changes in the amount of net shortwave radiation received on the earth’s surface. the results of the investigation of three cases of widespread dust in the province showed that in these three cases of widespread dust, aerosol particles are generally in the central, southern and western parts of the province (plain and lowland areas of the province) from the type of medium to large particles (index angstrom between 0.5 and 1) and in the eastern and northeastern parts, it was of the type of coarse particles (angstrom index less than 0.5). in the context of the impact of dust events on the amount of shortwave radiation received by the earth’s surface, it was seen that in the dust event of july 22, 2010, the angstrom exponential index indicates the presence of coarse particles in the atmosphere near the earth’s surface and the aod index also indicates the presence of dense dust in the entire area of the province. the received net shortwave radiation (at 12 noon or 09 utc) was about 194 watts per square meter (about 28 percent) lower than the average for the same month. this drop rate was less in the other two dust waves, whose aod and angstrom index values indicated finer and less concentrated dust. in the dust wave of june 19, 2012, the amount of net shortwave radiation received was only 5% (25 w/m2 at 12 noon or 09 utc) less than the long-term average, and this drop in the dust event of may 12, 2018 was equal to 28 w/m square (about 4% drop compared to the average of the same month).