پایش گرد و غبار و بررسی ارتباط آن با عوامل توپوگرافی، اقلیمی و پوشش گیاهی در استان خوزستان

طوفان گرد و غبار، فرایند پیچیده‌ای است که تحت‌تاثیر فعل ‌و انفعالات سامانه‌های جوّی قرار دارد و اساساً شرایطی مانند سرعت زیاد باد، خاک برهنه و هوای خشک باعث ایجاد آن می‌شود. محصولات آئروسل modis، پرمصرف‌ترین محصولات در مقیاس منطقه‌ای و جهانی در مطالعات گردوغبار هستند. این مطالعه با هدف پایش گردوغبار و بررسی ارتباط آن با عوامل مختلف توپوگرافی (درجۀ شیب، جهت شیب و ارتفاع)، پوشش گیاهی و اقلیم (عامل بارش) با استفاده از رگرسیون خطی و به کمک تکنیک‌های سنجش از دور و سیستم اطلاعات جغرافیایی در استان خوزستان صورت گرفت. نتایج ارتباط گردوغبار با عوامل ذکرشده نشان داد از بین تمام عوامل، ارتفاع و جهت شیب بیشترین همبستگی به‌ترتیب (83 درصد) و (72 درصد) را با پدیدۀ گردوغبار در جهت عکس ‌دارند؛ به‌طوری‌که افزایش در مقدار ارتفاع باعث کاهش گردوغبار و جهت‌های رو به جنوب و مناطق هموار، افزایش در مقدار این پدیده را خواهند داشت. بررسی معناداری همبستگی میان عامل گردوغبار با فاکتورهای درجۀ شیب، جهت شیب، بارش و ارتفاع با استفاده از آمارۀ p-value و در سطح 95 درصد اطمینان انجام گرفت. مقدار p-value به‌ترتیب برای هرکدام از عوامل مذکور به‌ترتیب 0.001، 0.00، 0.00 و 0.004 به دست آمد. براساس نتایج به‌دست‌آمده، بین گردوغبار و عوامل درجۀ شیب، جهت شیب، بارش و ارتفاع رابطۀ معناداری برقرار است. نتایج این پژوهش نشان داد که با بهره‌گیری از تکنیک‌های سنجش‌ از دور می‌توان به شناسایی کانون‌های گردوغبار به‌عنوان ابزار ارزشمندی به‌منظور مبارزه با عامل بیابان‌زایی استفاده کرد.

dust monitoring and investigation of its relationship with topographical, climatic and vegetation factors

introduction: airborne particles play an important role in the balance of atmospheric radiation and climate change. the relationship between aerosols and climate systems has received increasing attention as our understanding of these issues increases. a dust storm is a complex process that is influenced by the interactions of atmospheric systems and is basically caused by conditions such as high wind speed, bare soil and dry air. materials and methods: aerosol optical depth (aod) is one of the most important parameters in the field of dust related research. aerosol optical depth actually refers to the distribution of dust aerosols in the atmosphere. in this research, the dust condition was investigated using the aod parameter of modis product. in order to investigate the relationship between environmental factors, ndvi was used. for each year, based on the total images taken, which is about 24 images per year, the average vegetation cover index was calculated in the google earth engine system as a time series. in this study, among the climatic factors, annual rainfall data from synoptic stations were used to investigate the effect of rainfall on the amount of dust changes in the period from 2013 to 2022. also, a 90-meter dem was prepared from the srtm sensor in order to prepare layers of slope percentage, slope direction and elevation classes. results: in the research, firstly, to evaluate the dust situation, the aerosol optical depth product was obtained from the modis sensor. in order to highlight and monitor as much as possible, the dust phenomenon of the months of june to september, corresponding to the late spring and summer season of each year, when the majority of dust storms are concentrated in these months, was chosen. after downloading the images, the 9-year statistical period (2013-2022) was considered as the studied statistical period in khuzestan province. the average optical depth of dust was obtained each year based on the images taken in the same year.the results show that most of the dust was spread in the years 2015, 2016, 2017 and 2018, so that a large part of the province faced the dust phenomenon in these years. the investigation of the dust situation in 2013 and 2014 showed that although most of khuzestan province is facing a relatively low average aod, the maximum aod value is related to classes with values of 0.71 to 1.5 and more than 1.5 located in the southwest. is the province; the maximum value of aod in these years was 2.82 and considering that aod is between zero and 5 in the mentioned years, the southern regions have faced a high average dust phenomenon.