Journal of Spatial Analysis Environmental Hazards

fa ارزیابی تغییرات طول دوره‌های خشک فصلی با روش ارزیابی گام‌به‌گام سوارا (SWARA) در ایران Evaluating changes seasonal in the length of dry spells with the step-by-step assessment method SWARA in Iran تخصصي Special پژوهشي Research چکیده جهت بررسی رفتار فصلی طول دوره‌های خشک از داده‌های بارش در مقیاس روزانه برای 44 ایستگاه سینوپتیک ایران و دوره‌آماری30 ساله (2018-1988) استفاده شد. بعد از یکپارچه‌سازی آماری داده‌ها، دوره‌های بلندمدت با تداوم بیش از 20 روز مبنای مطالعه قرار گرفتند. در گام بعدی برای تعیین وزن فصلی دوره‌ها از روش ارزیابی گام‌به‌گام  منطق فازی‌-‌عددی سوارا(SWARA)، استفاده شد. در چهار گام اساسی اهمیت نسبی دوره‌های پرتکرار، وزن اولیه، وزن نهایی و نرمال شده دوره‌ها مشخص شد. اثرگذاری و وزن هرکدام از معیارها با روش سوارا در محیط فازی نشان داد که در مناطق غربی و شمالی کشور، بیشترین وزن اولیه در تبیین دوره‌ها را فصل زمستان و بهار و معیارهایی مانند برگشت‌پذیری و درصد احتمال رخداد دارا هستند. در تبیین نهایی نیز  این دو فصل وزن بالایی داشتند. این دو فصل بیش از 65 درصد وزن دوره‌ها در این مناطق را تبیین می‌کنند. در مناطق جنوبی و بخش‌هایی از مرکز(اصفهان، شرق فارس و غرب کرمان)، فصل زمستان و پاییز بیش از 71 درصد وزن‌ دوره‌ها را تبیین می‌کنند. در بین معیارهای تبیین‌کننده وزن دوره‌ها نیز معیار برگشت‌پذیری و احتمال رخداد  بیش از 55 درصد وزن را به خود اختصاص داده است. تغییرپذیری معیارها در مناطق شمالی و مرطوب کشور از برگشت‌پذیری، تداوم و احتمال رخداد بیشتری برخوردار است. این امر حاکی از این امر است که مرز مناطق خشک در آینده اقلیم ایران به سمت مناطق شمالی جابه‌جا می‌شود. می‌توان اذعان نمود که رفتار دوره‌های خشک بلندمدت بیشتر تابعی از دو معیار برگشت‌پذیری و احتمال رخداد آن‌هاست.   Abstract Introduction and issue: In today's century when the effects of climate change on different sectors are undeniable, investigating and analyzing the behavior during dry spells is always of special importance and basic priority. On the other hand, the occurrence of extreme events such as precipitation can accelerate the occurrence of climate change. In Iran, rainfall is one of the basic variables for evaluating the potential availability of water resources, but its temporal and spatial distribution is very uneven. The change of dry Spells depending on precipitation always have different fluctuations in different seasons of the year. It seems that this is due to the inherent behavior of precipitation, which generally shows itself as an unstable and unruly variable. This feature causes changes and differences in the temporal and spatial distribution of precipitation in arid and semi-arid regions such as Iran. This inconsistency will face fundamental challenges to regularize dry spells on a seasonal and monthly scale. With a detailed understanding of the behavioral mechanism of dry spells, it is possible to know more precisely the climatic condition of different regions in order to plan in sectors such as; Water resources, agriculture, health, transportation and etc we able to do basic and preventive measures compatible with climate change. It is hoped that this research and related studies will be a positive step towards a more accurate understanding of the climate and its behavior in different seasons of the year. Data and method: In order to investigate the seasonal behavior of the duration of dry spells, we used daily precipitation data for 44 synoptic stations of Iran and a 30-year statistical period (1988-2018). To reveal the behavior of dry spells, the precipitation data after validation and temporal integration were classified on a seasonal scale. After the statistical integration of the data, dry spells related to precepitation were extracted and long-term periods lasting more than 20 days were the basis of the study. In the next step, to determine the seasonal weight of courses was used, the step-by-step evaluation method of Swara's fuzzy-numerical logic (SWARA). Thus, in the first step, the longest and most frequent periods are sorted based on relative importance. In the second step, the initial weights of the courses are determined, and in the third and fourth steps, the final and normalized weights of the courses in different seasons are determined, and unrealistic results are removed from the final analysis for proper explanation. Findings and Results: The effectiveness and weight of each of the criteria with the Swara method in the fuzzy environment showed that in the western and northern regions of the country, winter and spring seasons and criteria such as reversibility and percentage of probability of occurrence have the most initial weight in explaining the periods. In the final explanation, these two season,s had a high weight. These two seasons explain more than 65% of the weight of courses in these regions. In the southern regions and parts of the center (Isfahan, East Fars and West Kerman), winter and autumn explain more than 71% of the weight of periods. Among the criteria explaining the weight of the courses, the reversibility criterion and the probability of occurrence have taken more than 55% of the weight. The northern and humid regions of the country vary in criteria from periods such as; Reversibility, continuity and probability of occurrence are more apparent and this indicates that the border of dry areas in the future of Iran's climate will move towards northern areas. It can be acknowledged that the behavior of long-term dry periods is more a function of two criteria of reversibility and probability of their occurrence. The weighting of the criteria affecting dry periods showed that the return period and the continuation of periods in the cold seasons of the year in dry areas have a more irregular behavior than in wet areas and have more weight in explaining the periods. By determining the weight of seasons in explaining dry periods, we can have better planning and management in related sectors such as water and agriculture. Key words: dry spells, weighing, precipitation, climate, Swara method, Iran.   واژگان کلیدی: تغییر اقلیم, وزن دهی, بارش, خشکسالی, روش سوارا Key words: Climate change, weighing, rainfall, drought, Swara method 143 156 http://jsaeh.khu.ac.ir/browse.php?a_code=A-10-1205-1&slc_lang=fa&sid=1 seyed keramat hashemi ana سید کرامت هاشمی عنا k.hashemi@yahoo.com 100319475328460011140 100319475328460011140 Yes university of yasouj دانشگاه یاسوج