پایش تغییرات زمانی-مکانی گرد و غبار معلق جوّ در استان های منتخب نیمه غرب ایران با استفاده از تصاویر MODIS و Sentinel- 5 (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
پژوهش حاضر با هدف پایش تغییرات زمانی و مکانی گرد و غبار معلق جوّ در قسمت هایی از نیمه غرب ایران در محیط گوگل ارث انجین با استفاده از کارآمدترین محصولات سنجنده مودیس در بازه زمانی (2012-2021) و تصاویر سنتینل-۵ برای دوره (2018-2021) انجام شد. برای این منظور روند تغییرات زمانی و مکانی غلظت هواویز با استفاده از تصاویر شاخص عمق نوری (AOD) و شاخص جذب آئروسل (AI) پایش و سپس شاخص بهینه پوشش گیاهی (EVI) و شاخص خاک لخت (BSI) حاصل از تصاویر MOD13Q1 برای بازه زمانی (2012-2021) محاسبه شد ودرنهایت، میانگین تغییرات آنها به دست آمد. تغییرات غلظت گرد و غبار معلق در جوّ با استفاده از شاخص AOD روند نزولی را در ماه ژانویه و روند صعودی را در ماه جولای نشان می دهد؛ درحالی که این غلظت در ژانویه سال 2021 کمترین و در ماه های جولای و سپتامبر سال 2021 بیشترین میزان آئروسل را با استفاده از شاخص AI داشته است. گروه بندی غلظت آئروسل ها در سه طبقه برای پهنه مطالعه شده نشان داد که مناطق با غلظت زیاد آئروسل بر اساس تصاویر مودیس و سنتینل شامل خوزستان و ایلام است که این طبقه بندی ها در تصاویر مودیس به صورت مداوم است؛ ولی در تصاویر سنتینل به صورت پراکنده است. هم پوشانی میزان غلظت گرد و غبار در تصاویر مودیس با شاخص های EVI و BSI نشان داد که بیشترین تمرکز آئروسل ها در مناطق فاقد پوشش گیاهی و خاک های لخت قرار دارد. نتایج این پژوهش به مدیران و برنامه ریزان کمک می کند تا با مدیریت اصولی پوشش گیاهی و کاهش خاک بدون پوشش گامی در راستای کاهش آلودگی های ناشی از گرد و غبار معلق در جوّ در این نواحی بردارند.Monitoring Temporal-Spatial Changes of Atmospheric Suspended Dust in Selected Provinces of the Western Half of Iran Using MODIS and Sentinel-5 Images
Dust is a significant global challenge. This study aimed to monitor the temporal and spatial changes of suspended atmospheric dust in the western half of Iran, specifically in the provinces of Ilam, Khuzestan, Kermanshah, Kurdistan, and Lorestan. We utilized MODIS sensor products from 2012 to 2021 and Sentinel-5 imagery from 2018 to 2021 within the Google Earth Engine framework. These sensor products are invaluable for managing and addressing dust-related issues. Using Aerosol Optical Depth (AOD) and Absorbing Aerosol Index (AAI) data, we tracked the trends in aerosol concentration over time and across the selected regions. Additionally, we calculated the Enhanced Vegetation Index (EVI) and Bare Soil Index (BSI) from MOD13Q1 images for the same period to assess their average changes. The analysis revealed a downward trend in AOD during January and an upward trend in July. The AAI indicated that January 2021 recorded the lowest aerosol levels, while July and September 2021 experienced the highest concentrations. Classifying aerosol concentrations into three categories highlighted that regions with high aerosol levels, as indicated by MODIS data, were consistently found in Khuzestan and Ilam provinces, while Sentinel data showed sporadic occurrences. Furthermore, the correlation between dust concentration from MODIS imagery and EVI and BSI indices revealed that the highest aerosol concentrations were located in areas with little vegetation and bare soils. Keywords: Western Half of Iran, Dust, Aerosol Optical Depth (AOD), Absorbing Aerosol Index (AAI), Enhanced Vegetation Index (EVI), Bare Soil Index (BSI). Introduction Dust has emerged as a significant contributor to air and environmental pollution worldwide. It can reduce horizontal visibility to less than 1,000 meters. With the increasing frequency of dust storms in recent years, monitoring these events has become crucial for identifying their sources. Given that dust can travel long distances from its origin, traditional measurement methods face time and spatial limitations. Therefore, satellite imagery and derived indices, such as Aerosol Optical Depth (AOD) and Absorbing Aerosol Index (AAI), are essential for effectively monitoring dust across extensive areas. Materials & Methods This study examined the temporal and spatial changes of dust in the provinces of Ilam, Khuzestan, Kermanshah, Kurdistan, and Lorestan. We utilized AOD from Terra and Aqua satellite images (MODIS sensor) for the years 2012-2021, along with AAI from Sentinel-5 (TROPOMI sensor) for the years 2018-2021. To analyze the trends and severity of dust changes, we employed the Enhanced Vegetation Index (EVI) and Bare Soil Index (BSI) derived from MOD13Q1 MODIS Terra images. Subsequently, we assessed the annual trends in AOD and AAI, generating spatial distribution maps of these changes. These maps were classified for the study period to facilitate a comprehensive understanding of dust dynamics in the region. Research FindingsAnalysis of the monthly time series for the AOD index revealed that the highest concentration of air pollutants in the studied provinces occurred in July 2012, while January consistently exhibited cleaner air throughout the period. Monthly variations in aerosol concentrations, as indicated by AAI satellite data, showed an upward trend in July and September due to elevated temperatures and reduced cloud cover and precipitation. Conversely, January saw a decrease in aerosol concentrations attributed to increased precipitation and lower temperatures. Yearly assessments of suspended dust concentrations using the AOD index indicated that 2012 and 2020 had the highest levels of aerosols. In Khuzestan and parts of Ilam Province, aerosol concentrations were notably high, identifying these areas as significant sources of dust. In contrast, Kurdistan and Lorestan provinces exhibited lower levels of suspended dust in the atmosphere. Based on the spatial distribution of dust density derived from MODIS and Sentinel-5 images, Khuzestan Province was classified as a high-risk area and served as an active center for dust generation. The spatial distribution of vegetation, as indicated by the EVI, revealed significant changes in vegetation in the northwest region of Khuzestan. In contrast, the southern parts of Khuzestan and the western areas of Ilam Province exhibited minimal vegetation changes alongside the highest dust concentrations during the study period. Discussion of Results & Conclusion The classification of aerosol concentrations into three categories revealed that areas with high aerosol levels, as indicated by MODIS images, were consistently found in Khuzestan and Ilam provinces, while Sentinel images showed these concentrations sporadically. The analysis of dust concentration in MODIS images, alongside the EVI and BSI, demonstrated that the highest aerosol concentrations occurred in regions characterized by minimal vegetation and bare soils. The findings of this study provide valuable insights for decision-makers aiming to manage areas with potential dust generation. Without effective management and planning, regions classified as medium-risk could gradually transition into high-risk areas, exacerbating the dust problem. The western regions of Kermanshah and Kurdistan provinces fell into a moderate category regarding vegetation. According to the BSI, most of the studied provinces featured bare soils, with only the western parts of Kermanshah, Kurdistan, and eastern Lorestan, along with central Khuzestan, displaying vegetation, water, and snow.
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