الگوهای همدیدی منجر به نابهنجاری‌های دمایی سه دهه اخیر در غرب و شمال غرب ایران

در این مقاله ناهنجاری‌ های دمایی و الگوهای همدیدی مرتبط با آن مورد واکاوی قرار گرفته است. برای این منظور داده‌های دمای روزانه 31 ایستگاه همدید برای بازه زمانی 1989 تا 2018 مرتب‌شده‌اند و با استفاده از شاخص نمره استاندارد z ناهنجارهای دمایی مشخص گردید. نتایج این تحقیق نشان داد در بیش از 50 درصد موارد دمای کمینه ماه‌های سرد در شرایط ناهنجار قرار دارد. فراوانی ناهنجاری‌ های منفی و مثبت به هم نزدیک است و با اختلاف جزئی دوره‌های گرم بیشتر تکرار شده‌اند. همچنین از نظر شدت غالب ناهنجاری‌ها از نوع ضعیف و متوسط هستند و رخدادهای شدید و بسیارشدید به‌ندرت اتفاق افتاده‌اند. نتایج همدید نشان داد که شارش نصف‌النهاری جریانات عرض‌های میانه علت اصلی ناهنجاری‌های دمایی این منطقه از کشور هستند. درالگو‌های غالب منجر به این شرایط، قرار گیری منطقه مورد مطالعه در ناحیه همگرایی بالایی پشته حاکم بر روی اروپا سبب فرارفت هوای سرد عرض‌های بالا و قرارگیری آن در ناحیه واگرایی بالایی ناوه بادهای غربی موجب فرارفت هوای گرم عرض‌های پایین شده است.

synoptic patterns leading to anomalies and temperature changes in the last three decades in western and northwestern iran

this climatehascharacteristics and behaviors that distinguish it from the surrounding areas.gradually, living and inanimateelements adapt to those conditions.as a result, any sudden change beyond the normal range and its normalbehaviorcauses theclimateof biologicalelements tobe stressedand stressed. these abnormalities maybe caused by climatechangeorlocal or human factors.in this study, we have tried to first examine the fluctuationsor changesin the temperature of the region in each of its parts in the last three decades.temperature anomalies were alsoassessed for sea level in the same three decades. synoptic patterns lead to anomalies in the temperature (hot and cold advection) are in cold season. in this study, atmospheric data of 31 stations from northwestern to western synoptic stations of iran were used. to create a database with the same statistical database, statistical periods from 1989 to 2018 are arranged. to detect climate change, the software for detecting climate change, provided by the (meteorological organization), has been used. the statistical period studied is divided into three ten-year statistical periods and the changes in these three statistical periods were calculated for all cold months. in another part of the work for the colder months of the year in three decades, the status of sea level temperature anomalies was also examined using ncep / ncar site maps.the standardized z index was used to identify the predominant synoptic pattern.the final selectioncriteria anomalies station high frequencyof 50% of the stations has been studied.so if the abnormalities are more frequent in the 15 stationandwas elected as a representative on the end of 202 days in the cold period has had this feature. also,sea level data were extracted in the same range for 202 days during a script.the data of sea level equationwas converted to numerical data by scripting in grads software environment, amatrix with dimensions of 203* 253 was analyzed by rotation with array in spss environment by factor analysis method, and by quarry ax method.eleven factorsjustify 95.40percent of climate behavior in the cold months. finally, after examining 11 factors, 4 dominant patterns were identified in this region.the results of this study showed that the temperature difference in northwestern iran with southwesternand middle western is decreasing. the temperature difference betweenthe southandthe north in thefirst decade (1989-1989) was between 7 and 9 degreescelsius, dependingon the month.in the second decade (1999-2008)this difference decreased to 5.5to 6.5 degreescelsiusand in thethird decade(2009-2018) it decreased to 5 to 6 degrees celsius.this means that the temperaturerangebetween the north and south of the country is declining.this means that the temperature range between the north and south of the country is declining. among the colder months,january had the highest temperature fluctuations and april had the lowest temperature fluctuations.if we exclude january, in other months, a total of three decades in the northern part of the study area, especially in ardabil province, the trend of increasing temperature changes and vice versa in the southern part of this increasing trend has had a slight slope. but in january, the phenomenon fluctuated sharply. in the second decade