آشکارسازی و تحلیل روند دمای ایران در تراز 1000 هکتوپاسکال

دما از عناصر اساسی شکل‌گیری اقلیم است و تغییرات آن می‌تواند ساختار آب و هوایی هر منطقه‌ای را دگرگون سازد و موجب تغییر در وقوع پدیده‌های حدی نظیر خشکسالی، بارش‌های سنگین و توفان ‌شود. لذا بررسی روند دما در مقیاس‌های مختلف زمانی و مکانی بخش بزرگی از تحقیقات اقلیم‌شناسی را به خود اختصاص داده است. این تحقیق به‌منظور آشکارسازی تغییرات دمای تراز 1000 هکتوپاسکال در فصول مختلف از سال 1950 تا 2020 میلادی در ایران صورت گرفته است. تحلیل‌ها بر روی متغیر میانگین ماهانه دما در طول دوره 70 ساله با استفاده از پایگاه داده ncep/ncar انجام گرفته است. نمودارهای سری زمانی متغیر مورد مطالعه با استفاده از آزمون من کندال در مقیاس سالانه ترسیم شدند. برای آشکارسازی و تحلیل روند دمای ایران در تراز 1000 هکتوپاسکال نقشه‌های میانگین 10 ساله و نمودارهای سری زمانی سالانه ترسیم شد، نتایج نشان داد میانگین سالانه دما در پهنه کشور ایران با آهنگ 1.34 درجه سانتی‌گراد (بالاتر از میانگین جهانی با مقدار0.74 درجه سانتی‌گراد ) در هر سده دارای روند افزایشی است. مقادیر متغیر میانگین سالانه دما در فصل‌های تابستان، پاییز و بهار دارای روند معنی‌دار بوده و میانگین دما در تراز 1000 هکتوپاسکال دارای روند صعودی است. بالاترین افزایش میانگین دمای تراز 1000 هکتوپاسکال متعلق به فصل تابستان بوده و با مقدار 0.2 درجه سانتی‌گراد به ازای هر 10 سال افزایش یافته است. نقشه‌های ده ساله میانگین دما در فصول مختلف نشان دادند نیمه جنوبی ایران در طول دوره مطالعاتی دارای روند افزایشی دما بوده است.

Detection and analysis of temperature trend at the 1000 hPa level in Iran

Extended AbstractIntroductionTemperature is considered to be an important element of climate whose changes have important consequences for human life. The present study seeks to detect trends and significant changes in the temperature at the 1000 hPa level in Iran. Due to its geographical location, Iran climate is affected by various patterns of sea level pressure such as subtropical highpressure, Siberian highpressure, Monsoon lowpressure, the Mediterranean low pressure, Black Sea low pressure and Sudan low pressure during warm and cold seasons. These patterns have changed in different time series leaving adverse effects such as decreased precipitation and increased temperature, while probably changing Iran climate from semiarid to arid and causing climate hazards. Having enough information on the temperature characteristics and its future trends, it is possible to decide on macro politics and a comprehensive method for the management of an area. Therefore, the present study aims to detect trends and significant changes in air temperature at the 1000 hPa level. Materials & Methods45 ° to 64 ° Eastern longitude and 45 ° to 64 ° latitude were selected to study temperature changes at the 1000 hPa level in Iran. In this study, temperature data of 1000 hPa level recorded in a 70year statistical period (1950 to 2020) and data retrieved from NCEP/NCAR with a spatial resolution of 2.5 by 2.5 degrees have been used to prepare time series and necessary maps. The Kendall Man test was used to analyze the trend of time series. The 70year statistical period (1950 2020) was divided into 10 decades and average seasonal temperature was used. Results & DiscussionThe average temperature of Iran at the 1000 hPa level is rising by 1.34° C per century and its standard deviation has reached its maximum value in recent decades. In the last two decades of the statistical period, 30 ° C contour line has approached Iran from southwest. Temperature trend at the 1000 hPa level is investigated in 4 different seasons of Iran.Summer: according to the MannKendall test, average temperature in summer shows a significant trend and has increased by 0.2 ° C every decade.Autumn: time series of temperature data in autumn shows a significant trend and the slope of the regression line (temperature) has increased with a rate of 0.0451 ° C every decade.Winter: average temperature has decreased at the beginning of the study series and increased at the end of the series. 15.26 ° C and 8.18 ° C (in 1966 and 1972) were the highest and the lowest average temperature recorded in winter, respectively.Spring:The average temperature in Iran has increased by 0.197 ° C every decade. In this 70year statistical period, average temperature of Iran in this season was 24.37 ° C with the highest annual average temperature recorded as 27.18 ° C in 2008 and the lowest annual average temperature recorded as 21.83 ° C in 1972 and 1992. ConclusionAverage temperature in Iran is raising with a rate much higher than the global average (0.74 ° C  per hundred years), due to wide fluctuations in the general circulation patterns of the atmosphere and changes in sea level pressure pattern. Thus, it can be predicted that the temperature in southern Iran may reach over 60 ° C by the end of the century threatening southern riparian provinces with dangerously rising water level and the risk of drowning. Wildfires will still be common in Iranian forests, the number and intensity of floods will increase sharply, and water resources will reach a critically low status.