تحلیل تاثیر رخداد هم ‌زمان برخی شاخص ‌های دورپیوندی نیمکره شمالی بر دمای زمستانه ایران

هدف اصلی این مطالعه، بررسی اثر هم‌ زمان دورپیوندهای نوسان اطلس شمالی (nao) و نوسان شمالگان (ao) با نوسان چند دهه‌ای اقیانوس آرام و نوسان آرام آمریکای‌شمالی و تاثیر آن بر دمای زمستانه ایران است. بدین ‌منظور، از داده های دمایی 100 ایستگاه هواشناسی سینوپتیک ایران در دوره آماری 1988-2019 استفاده شد. نتایج نشان داد که ارتباط معکوس و معنی‌داری بین دورپیوندهای نوسان شمالگان و نوسان اطلس شمالی با دمای اغلب مناطق ایران در ماه فوریه وجود دارد. نتایج همچنین نشان داد که هم‌زمانی وقوع فازهای مثبت نوسان اطلس شمالی و نوسان شمالگان با فازهای منفی و خنثی نوسان چند دهه‌ای اقیانوس آرام و الگوی آرام آمریکای‌شمالی، موجب رخداد دمای نرمال و کمتر از نرمال در اغلب مناطق ایران به‌خصوص بخش‌های غربی می‌شود در صورتی‌که، هم‌زمانی وقوع فازهای منفی نوسان اطلس شمالی و نوسان شمالگان با فازهای منفی و خنثی نوسان چند دهه‌ای اقیانوس آرام و فازهای خنثی و مثبت الگوی آرام آمریکای‌شمالی موجب رخداد دمای بیشتر از نرمال در بخش‌های شمالی ایران می‌شود. همچنین، هم‌زمانی فازهای خنثی نوسان اطلس شمالی و نوسان شمالگان با فازهای مثبت و منفی نوسان چند دهه­ای اقیانوس آرام و فازهای خنثی و مثبت الگوی آرام آمریکای‌شمالی موجب رخداد دمای نرمال و بیشتر از نرمال در نیمه غربی و شمالی ایران می‌شود در صورتی ‌که در هنگام رخداد هم‌زمان فازهای خنثی همه دورپیوندهای مذکور، تغییرات منظم دمایی در ایران مشاهده نمی‌شود.

analysis of the effect of the simultaneous occurrence of some teleconnection indices of the northern hemisphere on the winter temperature in iran

air temperature is very important among the climatic elements. since iran is located in the subtropical region, extreme temperature changes are one of its inherent characteristics, and for this reason, investigating temperature changes in iran is essential. fluctuations in temperature on a large and regional scale are more or less influenced by teleconnection patterns. this article aim is to investigate the simultaneous occurrence of the north atlantic oscillation (nao) and the arctic oscillation (ao) with the pacific-north american (pna) and the pacific decadal oscillation (pdo) and their effect on iran’s winter temperature.in this research, the monthly temperature data of 100 selected synoptic stations of iran from the islamic republic of iran meteorological organization (irimo) website and the pdo, pna, nao, and ao indices from the national oceanic and atmospheric administration (noaa) website for 1988-2019 were obtained as primary data. to determine pearson’s correlation coefficients, normalized monthly temperature data were entered into statistica software as a dependent variable and teleconnection data as an independent variable. then, the positive and negative phases of the mentioned teleconnections were identified. numbers smaller than -0.5 were considered as the negative phase, between -0.5 and 0.5 as the neutral phase, and greater than 0.5 as the positive phase. then, the monthly temperature anomaly was calculated for the mentioned months. the distribution of temperature anomaly changes in iran was zoned in the gis software using the inverse distance weighted (idw) method.the results of examining the relationship between the studied variables and the winter temperature of iran showed that there is significant inverse relationship between the ao index and the temperature of december, january, and february in most regions of iran, especially in the western regions so, correlation coefficients can be seen in the northwestern regions of iran up to -0.66. also, in most investigated stations, there is a significant inverse relationship between the nao index and the february temperature was observed, so the correlation coefficient was observed in the western parts of iran up to -0.62. by increasing the numerical values of the studied teleconnections from negative to positive phases, the temperature of most regions of iran decreases throughout the year, especially in february. in some studied stations, a direct and significant correlation was observed between the negative phases of pna with january temperature and the negative phases of pdo with december temperature. by reducing the numerical values of pna and pdo teleconnections from neutral to negative phases, the temperature of some regions of iran decreases. the coincidence of the positive phases of nao and ao with the negative and neutral phases of pdo and pna has caused the occurrence of normal and lower-than-normal temperatures in most regions of iran, especially the regions located in the northern and western half, so, the coldest months of the statistical period happened in this state.