مدل سازی و پایش پدیده خشکسالی در شمال غرب ایران

خشکسالی مختص مکان خاص نبوده و مناطق مختلف جهان از آن متاثر می باشد، یکی از این مناطق، شمال غرب ایران است که در چند سال اخیر از این پدیده رنج می برد. هدف پژوهش حاضر مدل سازی و تحلیل خشکسالی در شمال غرب ایران می باشد. برای این کار پارامترهای اقلیمی: بارش، دما، ساعات آفتابی، حداقل رطوبت نسبی و سرعت باد در بازه زمانی 32 ساله (2018-1987) در 21 ایستگاه شمال غرب ایران مورد استفاده قرار گرفت. برای مدل سازی، شاخص فازی t.i.b.i ابتدا چهار شاخص (set, spi, seb, mczi) با استفاده منطق فازی در نرم افزار matlab فازی‌سازی شدند، سپس شاخص‌ها با هم مقایسه شده و درنهایت از مدل تصمیم گیری چند متغیره topsis، برای اولویت‌ سنجی مناطق درگیر با خشکسالی استفاده شد. یافته های پژوهش نشان داد مدل t.i.b.i طبقات خشکسالی، چهار شاخص مذکور را به‌صورت دقیق در خود منعکس می کند. از بین 5 پارامتر اقلیمی مورد استفاده در این پژوهش، پارامتر دما در نوسان شدت خشکسالی بیش ترین تاثیر را داشت. شدت خشکسالی براساس مدل‌ سازی صورت گرفته در مقیاس 12 ماهه بیش تر از 6 ماهه بود، طولانی ترین تداوم خشکسالی در منطقه مورد مطالعه مربوط به ایستگاه ارومیه در بازه 12 ماهه از ماه جولای سال 2003 تا ماه دسامبر سال 2004 به مدت 18 ماه رخ داده است. بیش ترین درصد رخداد خشکسالی در ایستگاه ارومیه در مقیاس 12 ماهه و کم ترین آن در ایستگاه سنندج در مقیاس 6 ماهه اتفاق افتاده است. براساس مدل سازی صورت گرفته، شاخص فازی t.i.b.i نسبت به شاخص فازی spei برتری نسبی را نشان داد.

Modeling and Monitoring the Drought Phenomenon in Northwest of Iran

; Introduction;;Drought is one of the natural hazards which can cause an irreparable damage in various sectors of agriculture, economics, and so on. In recent years, different regions of the world have experienced more severe drought (Mirzai et al., 2015). Also, drought is one of the most important natural disasters affecting agriculture and water resources which is abundant especially in arid and semiarid regions (Shamsenya et al., 2008). Drought changes are wellsuited for optimal management of water resources utilization (Alizadeh, 2017). Drought is also referred to as a climate phenomenon with a lack of humidity and rainfall relative to normal conditions. This phenomenon strongly affects all aspects of human activity (Zeinali Safarian Zangir, 2017). Regarding the studies done inside and outside of the country, this study attempted to model and monitor the drought phenomenon in northwest of Iran using a new index.;;Materials and Methods;;In this study, drought modeling in northwest of Iran was carried out using climatic data of rainfall, temperature, sunshine, relative humidity, and wind speed monthly (6 and 12 months scale) for the period of 32 years (19872018) in five provinces of Ardebil, East Azarbaijan, West Azarbaijan, Zanjan, and Kordestan in 21 stations using a new index modeling called TIBI architecture, fuzzyized from four indicators (SET, SPI, SEB, MCZI) Valid in World Meteorological Organization. The position of the studied areas are shown in Fig. 1 and the coordinates of the stations are presented in Table (1).;;Results and Discussion;;Monitoring of drought fluctuations based on four integrated indicators in T.I.B.I;In order to investigate the effect of drought fluctuations in drought conditions of stations, it is possible to find changes in the parameters (SET, SPI, SEB, MCZI) within the TIBI index. Considering the large number of stations studied, for the sake of better understanding, only the drought series chart of Tabriz station was presented on two 6and 12month scale. (In the abovementioned Station diagram, the Flash line Red shows a 6monthold drought margin with a value of 0.44 and more, and a 12month scale with a value of 0.98 and more). The analysis of these forms shows that at the 6 and 12month scale of Tabriz station, the amount of evapotranspiration was similar to drought conditions, which decreased from March 1993 to July 1998, while after this month an increase was observed. The impact of rainfall on a 6month scale is weaker than the 12month scale. From April 1996 to December 2004, it has grown steadily, and then followed the same pattern. The indicators (SET, SPI, SEB, MCZI) affect the TIBI index and show some trends indicating that the new TIBI fuzzy index is well reflected in the four indicators. Its drought classes scale was presented in Table 5. The T.I.B.I index on a 12month scale shows a sharper shape compared to a sixmonth scale.;;Conclusion;;In recent years, drought is one of the most important damaging issues in different sectors such as agriculture, economics, etc. In different parts of Iran including Northwest of Iran, Researchers have done a lot of research on drought monitoring. They presented different models but did not adequately cover the subject. The purpose of this study was to model and investigate drought in northwest of Iran during the 6 and 12month scale. At stations, the intensity of the 12month scale and the frequency of droughts are more than 6 months. Drought persistence is more than 12 months old. Drought had a lower continuity in the shortrun time scale and was influenced by the temperature parameter. The severity of drought in the long periods of time was less responsive to rainfall variations. The trend of drought in the northwest of Iran increased and the temperature trend was mildly increasing. The most frequent occurrence of drought occurred at the 6th and 12th month scale in Orumiyeh station, while the lowest in both the 6 and 12month scale in Sanandaj station. The percentage of drought frequency in Jolfa, Maku, and Uromieh stations was 12 months higher than the 6month scale.