Journal of Spatial Analysis Environmental Hazards

fa ارزیابی داده های زمینی و تصاویر ماهواره ای در تحلیل گرد و غبارهای نیمه غربی ایران Assessment of ground-based dataset and satellite remotely sensed images for analyzing of dust over western Iran تخصصي Special پژوهشي Research <div style="text-align: justify;">طوفان گرد و غبار فرایند پیچیدهای است که تحت تاثیر تعامل سیستم اتمسفر–زمین بوده و از نظر اقلیمشناسان و هواشناسانی که تغییرهای اقلیمی و اتمسفری را بررسی میکنند، پایش پوشش گرد و غبار یک پدیده دینامیکی مهم است. در این مطالعه با استفاده از دادههای دید افقی و سنجش از دور ماهوارهای (MODIS) و شاخص NDDI به آشکارسازی گردوغبار در نیمه غربی ایران پرداخته شده است. طبق بررسیهای انجام شده، نقشه میانیابی تعداد روز غبارآلود در نیمه غربی ایران نشان داد که محدوده مورد مطالعه غرب ایران از لحاظ فراوانی وقوع پدیده گرد و غبار و چگونگی روند آن دارای نظام همگنی نیست و تعداد روزهای گرد و غباری از شمال به سمت جنوب افزایش مییابد. هسته بیشینه وقوع پدیده گرد و غبار در بخش جنوبغربی منطقه و بر روی اهواز، امیدیه و بوشهر  قرار دارد که با منشاٌ مناطق بیابانی در عراق-سوریه و عربستان است. نتایج پراکنش فضایی دید افقی ایستگاههای زمینی با آشکارسازی شاخص NDDI بر روی تصاویر مطابقت دارد و نشان داد که بیشترین سطح پوشش گردوغبار بر روی اتمسفر استانهای فارس و بوشهر و کمترین مقدار آن در سطح استانهای آذربایجان غربی و شرقی، قم و مرکزی مشاهده میشود.</div> <div style="text-align: justify;">Introduction Dust storm is a complex process affected by the earth-atmophere system. The interaction between the earth and atmosphere is in the realm of the climatologists and meteorologists, who assess atmospheric and climatic changes, and monitor dust spread. Dust is the main type of aerosols which affects directly and indirectly radiation budget. In addition, altogether they affect the temperature change, cloud formation, convection, and precipitation. The most important studies about dust analysis have considered the use of remote sensing technique and global models for analyzing the behavior and dynamics of dust in recent two decades. To achieve such a goal, this paper has used MODIS and NDDI data to study and identify the behavior of atmospheric dust in half west of Iran. Materials and methods The western region of Iran is the study area. The data used in this study are divided into two categories: ground-based observations in 27 synoptic stations extracted from the Iran’s Meteorological Organization during the period (1998-2010) and satellite MODIS images during the first to fourth days of July 2008 as atmospheric dust extremes. Data was analyzed by using ArcGIS and ENVI software and NDDI index.  Results and Discussion According to results, interpolated map for the number of dusty days during the study period over the western half of Iran showed that the scope of study area does not involve an equal system aspect quantity of occurrences. The number of dusty days occurrences increase from north toward south and the sites located in northern proportions of the area have experienced lower dust events. In contrast, maximum hotspots are occurring over southwestern sites such as: Ahvaz, Ilam, Boushehr and Shiraz. Therefore, principal offspring of dust input has been out of country boundaries and arrived at distant areas. Also, based on results obtained using satellite remote sensing images and applied NDDI index, maximum of intense dust cover is observed over Fars, Ilam, Boushehr and Ahvaz provinces on the first, second, third and fourth of July. However, the lowest rate of index situated in extent far such as: East and West Azerbaijan provinces. Thus, parts located on the north of the study area experienced less dusty days and the maximum dust cores were located in the southwestern (mostly Khuzestan). The long-term results were consistent with the daily average of NDDI index in the whole study area and indicated the hotspot areas (Ilam, Ahvaz, Omidyeh, Bushehr and Shiraz) during the first to fourth days of July 2008. However, the level of dust cover in the region has reduced when a wet and cloudy synoptic system passes over the central and northwestern parts of the study area. Conclusions The climatic interpolated map interpretation indicated that increase of dust concentration based on ground-based stations, which are consistent with dust concentration, is overshadowed by the latitude and proximity of sources of dust source in the Middle East. Also, the long-term climatic results of ground-based observations were consistent with the NDDI index calculated on dust extremes in the whole study area and in the southern areas (Ilam, Ahvaz, Omidyeh, Bushehr and Shiraz) during study days of July, 2008. Therefore, dust occurrence increases from north to south and the maximum hotspots over southwestern confirm the proximity of the south western region of Iran to deserts and sedimentary plains and their direct relationship with dust sources in the Middle East. These regions highlight the volume and expansion of dust outbreaks, which were well detected due to the satellite imagery and spectral characteristics of MODIS for monitoring changes in the dust phenomenon. Overall, the use of satellite remotely sensed data/images not only cover the ground-based observation datasets gap to identify, highlight, and analyse the dust phenomenon, but also takes a much more geographical approach in analysing environmental hazards such as dust. It is also suitable for studies of atmospheric compounds such as atmospheric aerosols.</div> تصاویر ماهواره ای, داده زمینی, شاخص NDDI, گرد و غبار, غرب ایران. Dust Storm, Remote Sensing, Ground-based stations, NDDI index, Western Iran 115 130 http://jsaeh.khu.ac.ir/browse.php?a_code=A-10-856-5&slc_lang=fa&sid=1 Kaveh Mohammadpour کاوه محمدپور kawe.m@hotmail.com 100319475328460011456 100319475328460011456 Yes PhD, Department of Climatology, faculty of Geographical Sciences, Kharazmi University, Tehran, Iran Ali Mohammad Khorshiddoust علی محمد خورشیددوست khorshid@tabrizu.ac.ir 100319475328460011457 100319475328460011457 No Professor, Department of Climatology, faculty of planning and Environmental Sciences, Tabriz University, Tabriz, Iran. Gona Ahmadi گونا احمدی Climatologist64@yahoo.com 100319475328460011458 100319475328460011458 No Master, Department of Climatology, faculty of Planning and Environmental Sciences, Tabriz University, Tabriz, Iran.