كليدواژه :
ماهواره اي , گرد و غبار , جنوب غرب ايران , ماهواره اي , تحليل همديدي , تصاوير MODIS
چكيده فارسي :
كشور ايران در كمربند خشك و بياباني جهان واقع شده است. حاكميت اين شرايط به تبعيت از موقعيت جغرافيايي آن، سازوكار لازم را براي وقوع رويدادهاي گردوغباري در بسياري از ايام سال فراهم كرده است. پديده ي مذكور طي سال هاي اخير با شدت و فراوني وقوع، مناطق عمده اي از ايران (به خصوص بخش هاي غربي و جنوب غربي) را متاثر كرده كه به لحاظ اقليمي و زيست محيطي، مطالعه و مديريت كاهش آثار آن در اولويت است. در اين پژوهش نيز رويداد گردوغباري كه در آبان 1396 اتفاق افتاد، با استفاده از شاخص هاي مبتني بر سنجش از دور چند زماني Terra/MODIS، تحليل هاي همديدي مبتني بر برونداد پايگاه ECMWF و پارامتر هاي هواسپهر از پايگاه NCEP/NCAR بررسي شد. بنابراين، بر حسب ويژگي هاي انعكاس و جذب رويداد غباري مذكور، محدوده ي غبار حاصله و شدت آن به گونه ي دقيق استخراج و درجه ي شدت آنها برآورد شد. سپس مسير حركت آن به وسيله ي داده هاي چند زماني Terra/MODIS مشخص شد. نتايج حاصل از بررسي ماهواره اي، بيانگر توافق زياد با پايش شرايط هواشناسي حاكم در زمان وقوع گردوغبار است. همچنين نتايج نشان داد كه شرايط جوي حاكم بر لايه ي مرزي هواسپهر، در ايجاد تلاطم و انتقال گردوغبار از بيابان هاي شمال عربستان، شرق و جنوب سوريه، و غرب و جنوب عراق به جنوب غرب ايران نقش مهم و انكارناپذيري دارد؛ به گونه اي كه در رويداد مورد مطالعه، شرايط هواسپهري ناپايدار همچون قرارگيري ناوهاي بسيار عميق، چرخند قوي همراه با تاوايي مثبت قابل توجه در محور ناوه و ناپايداري و صعود هوا، زمينه را براي ايجاد شرايطي ناآرام و متلاطم بر فراز نواحي بياباني كشورهاي عربي همجوار با غرب ايران، فراهم و شرايط بسيار مساعدي براي برداشت، حمل و انتقال آن به نواحي غرب و جنوب غرب ايران مهيا كرده است.
چكيده لاتين :
Dust storms are a kind of severe natural disaster indust source regions, which have a negative impact on human health, industrial products and activities. Iran is a dry and low water country, the coincidence of this situation and its position in the global rebound belt has brought about very bad conditions. Repeaters in recent years have been affected by the severity and frequency of major events in Iran and, in terms of environmental issues, studying and managing the reduction of its effects is a priority.
In recent years, these events have been the main hazards in areas of South-west Iran. Several complex dust storms have recently occurred in the southwestern part of Iran. Detecting the spatial distribution of dust storms in the deposition regions is an essential step for managing this natural and human-induced crisis. Land measurement and remote sensing techniques are currently two of the most important methods for monitoring dust storms. Traditional reference land measurement methods have little spatial and temporal resolutions, so they can not properly monitor and anticipate dust storms. Due to rapid changes in the nature and location of dust storms, there are limitations in monitoring and relating measurements. Meteorological numerical models can not detect dust storms alone. Today, remote sensing technology is known for providing multiple global and regional images with time, spatial and spectral scales as a useful tool for monitoring , measuring and harvesting dust properties. Also, remote sensing can monitor the range and scope of dust storms, their degree of intensity and their route of movement. In this research, by using MODIS images and applying methods of applying the dust algorithm, dust was monitored. This study aimed to investigate the performance of the Normalized Differences Dust Index (NDDI) applied to MODIS data (01/11/2017) for detection of dust storms in the Southwest of Iran.
Methodology
Monitoring disasters properly is a necessary requirement. In this study, the dust event that took place in November 2017, based on Terra / MODIS remote-sensing indices, has been monitored by ECMWF database and synoptic analyzes from the NCEP / NCAR database. Therefore, according to the characteristics of reflection and absorption of the aforementioned dust event, the resulting dust range and its intensity are extracted accurately using the NDDI index and their degree of intensity is estimated. The NDDI equation is as follows: Here b3 and b7 reflect the band of three and the band of seven of the MODIS bands.
Results
Based on the results, the dust pollution eventually increased the air pollution in some areas of Khuzestan, Ilam, Kermanshah and Kurdistan provineces, and greatly reduced the horizontal visibility. The results also showed that the dust storm began from the day in which it started from deserts in the northeast of Saudi Arabia, and after spreading to the vast deserts of southern Syria, northern Arabia and west of Iraq, moving eastward to southwest Iran has moved. The maximum spatial distribution of dust is in Khuzestan province. After the Khuzestan province, western parts of Ilam, Kermanshah, Kurdistan and Zanjan provinces are located in the next rows. Discussion & Conclusions: The results of the satellite monitoring show a great deal of agreement with monitoring the meteorological conditions at the time of the occurrence of dust. The results also showed that the atmospheric conditions affecting the Atmosphere borderland in creating turbulence and transferring dust from deserts in northern Arabia, east and south of Syria, west and south of Iraq to southwest Iran have an important and undeniable nature. So, in the dusty event studied, unstable airborne conditions, such as the presence of very deep wrecks, a strong wheel with a significant positive tau in the wake axis, along with instability and climbing the air, made the region an unrestrained and turbulent situation over adjacent Arabian desert areas Provided with the West of Iran and provided very favorable conditions for harvesting, transportation and transportation to the western and southeastern parts of Iran.
