تحلیل الگوی فضایی وضعیت خشکسالی در زاگرس میانی و جنوبی با استفاده از شاخص‌های سنجش از دور

خشکسالی یکی از جدی‌ترین مخاطرات طبیعی است که بر کیفیت زندگی همۀ موجودات زنده تاثیرگذار است. ایران سرزمینی کم‌باران است که طی اعصار، با تهدید این مخاطرۀ طبیعی مواجه بوده است. هدف این مطالعه بررسی شاخص‌های سنجش از دوری بیانگر خشکسالی و تبیین الگوی خودهمبستگی فضایی در زاگرس میانی و جنوبی است. در این راستا با بهره از آمار روزانۀ بارش 103 ایستگاه هواشناسی طی دوره‌های زمانی 2000 تا 2019 داده‌های مورد نیاز تهیه و مقادیر spi متناظر ایستگاه‌های مذکور مربوط به ایستگاه‌های هواشناسی استخراج شد. سپس شاخص‌های ndvi، vci، tci، vhi، ddi، nddi، evi، ndwi و savi بر 240 تصویر سنجندۀ مودیس اعمال و نقشه‌های خشکسالی تهیه گردید و عوامل موثر به‌کمک تحلیل عاملی و الگوی فضایی شاخص خشکسالی با شاخص‌های سنجش از دور و تحلیل فضایی، تجزیه و تحلیل شدند. نتایج حاکی از کارایی بهتر شاخص‌های savi، ndvi، vci و evi در بررسی خشکسالی بوده است. همچنین شاخص spi با بیشتر شاخص‌های پوشش گیاهی، الگوی خودهمبستگی فضایی مثبتی را نمایان کرده است؛ این در حالی است که در بین شاخص‌های یادشده vhi کمترین اثربخشی را در تحلیل خشکسالی ارائه کرد.

analyzing the spatial pattern of drought in central and south zagros using remote sensing indicators

introduction: as a complex phenomenon occurring due to a long period of poor precipitation, drought causes water scarcity in the soil and the hydrological system via hydrological, bringing about longterm consequences which may lead to severe economic, environmental, and social problems worldwide. droughts are classified into four types: meteorological (rainfall), agricultural (soil’s moisture), hydrological (flow and groundwater), and socioeconomic droughts. it should be noted that all types of droughts originate from meteorological ones, bringing about social and economic damages. on the other hand, iran has long been known as a dry country with a low annual precipitation rate. moreover, the development of spatial and satellite sciences, the application of remote sensing techniques, and gis together with previous methods have led to more accurate results. therefore, investigating the relationships between satellitederived indicators and meteorological droughts could improve our understanding of the response of such indicators to climate change.research methods: this study sought to investigate the relationship between remote sensing indices and the drought index (spi). to this end, first, the daily precipitation statistics of 103 meteorological stations located in the study area were collected from the iranian meteorological organization’s website for the 2000 2019 period and their quality was controlled. then, the spi drought index was measured for all such data on monthly and annual scales using the mckay method, according to which the total annual precipitation was compared to the fit of different distributions. then the probability of the observations’ experimental occurrence was calculated based on the relationship between the aforementioned equations. moreover, after measuring the spi index in the stations located in the study area, the mod021km outputs of the terra sensor for the 20002019 period were obtained from the usgs website, to which necessary geometric, radiometric, and atmospheric corrections were applied. finally, the ndvi, vci, tci, vhi, ddi, nddi, evi, ndwi, and savi indices were used to assess the drought conditions, and a monthly time series database was created for each of the indices over the past 20 years.