ارزیابی اثرات تغییر اقلیم بر طبقه‌بندی اقلیمی ایران

موضوع تغییر اقلیم به‌دلیل پیامدهای آن بر تمام ابعاد زندگی بشری، یکی از مباحث مهمی محسوب می‌شود که بررسی تاثیرات مختلف آن علاقه‌مندی فراوانی میان پژوهش‌گران به‌وجود آورده است. تاثیرات تغییر اقلیم می‌تواند باعث افزایش یا کاهش در سطح یک منطقه‌ اقلیمی شده و در نتیجه موجب جابه‌جایی مناطق اقلیمی شود. هدف از این پژوهش ارزیابی اثرات تغییر اقلیم بر طبقه‌بندی اقلیمی ایران است. در این پژوهش از داده‌های 120 ایستگاه سینوپتیک در دورۀ آماری 2022-1993 استفاده شده است. به‌منظور بررسی تاثیرات تغییر اقلیم در دوره‌های آتی، برونداد مدل canesm2 از سری مدل‌های cmip5 تحت دو سناریوی rcp2.6 و rcp8.5 مورد استفاده قرار گرفته و ریزمقیاس‌سازی با مدل lars-wg انجام شده است. با توجه به نتایج، قسمت اعظم ایران (49/90 درصد) اقلیمی خشک و نیمه‌خشک دارد، به‌طوری‌که اقلیم خشک 82/68 درصد و اقلیم نیمه‌خشک 97/21 درصد از آن را تشکیل می‌دهند. بنابراین، باید ایران را از نظر اقلیمی کشوری خشک و نیمه‌خشک نامید. با بررسی تاثیرات تغییر اقلیم مشاهده می‌شود که در دوره‌های آتی میزان بارش و دمای میانگین سالانه افزایش خواهد یافت و این افزایش تحت سناریوی rcp8.5 بیش‌تر از سناریوی rcp2.6 خواهد بود. بررسی طبقه‌بندی اقلیمی ایران در دوره‌های آتی نشان می‌دهد که بیش‌تر مساحت ایران در اقلیم خشک و نیمه‌خشک باقی خواهد ماند. مجموع اقلیم‌های خشک و نیمه‌خشک در دورۀ 2041-2020 و تحت سناریوی rcp2.6 به کم‌ترین میزان خود خواهد رسید و پس از آن، دوباره این اقلیم‌ها گسترش خواهند یافت. طبق سناریوی rcp8.5 در دوره‌های 2041-2021، 2060-2041 و 2080-2061 مجموع مساحت اقلیم‌های خشک و نیمه‌خشک کاهشی خواهد بود، اما پس از آن و در دورۀ 2100-2081 این روند برعکس شده و افزایش این اقلیم‌ها را شاهد خواهیم بود. با توجه به نتایج این پژوهش و طبق پیش‌نگری انجام یافته، هرچند که طبق سناریوهای انتشار متفاوت، تفاوت در مساحت طبقه‌های مختلف دیده می‌شود، اما در آینده نیز هم‌چنان طبقه‌های اقلیمی خشک و نیمه‌خشک قسمت اعظم ایران را تشکیل خواهند داد. نتایج این پژوهش به‌دلیل قرارگیری ایران در اقلیم خشک و نیمه‌خشک، لزوم توجه به پدیدۀ تغییر اقلیم و ضرورت توجه صاحب‌نظران و برنامه‌ریزان کلان کشوری به تاثیرات این پدیده را نشان می‌دهد.

evaluating the effects of climate change on the climatic classification in iran

introductionthe average weather condition in a specific region is defined as climate. the diversity of climatic variables is effective in determining the climate of a region and causes the formation of diverse and different climates. one of the effects of climate change is that causes an increase or decrease in a climate zone and, as a result, a shift in climate zones. climate classification is an attempt to identify and recognize the differences and similarities of climate in different regions and to discover the relationships between different components of the climate system. climate classification indicators are used to visualize current climate and quantify future changes in climate types as predicted by climate models. the studies conducted on these methods show that climatic variables affecting experimental methods such as temperature and precipitation should be considered effective variables in determining climatic boundaries in a new way. the de martonne aridity index is an empirical index for climate classification based on two components, precipitation and temperature. due to its high accuracy, and the use of variables that are more accessible and can be measured at most meteorological stations, de martonne’s index has received more attention from researchers and has been used in many studies of climate change. therefore, the purpose of this research is to evaluate the effects of climate change on the climatic classification of iran. materials and methodsto investigate the effects of climate change on the climatic classification of iran, the de martonne aridity index has been used. to show the effects of climate change in the past and the future on iran’s climate, data from 120 meteorological stations of iran, which are distributed in different locations with different climates, were collected and analyzed in the statistical period of 1933-2022. the climatic condition of iran in the base period was determined according to the de martonne aridity index. in addition, to investigate the effects of climate change in the coming periods on the climatic classification of iran, the data related to the output of the canesm2 model, which is one of the cmip5 models that is hybridized by the canadian center for climate modeling and analysis (cccma) by combining cancm4 and ctem models, were used. to examine the changes in climatic classes of iran under different scenarios and conditions, the output of two release scenarios, rcp2.6 and rcp8.5, were utilized. due to the large-scale output of general circulation models (gcm), the output of this model was downscaled using the lars-wg model. the lars-wg model, which is considered one of the most famous and widely used models for downscaling weather data, was used to generate precipitation values, minimum and maximum temperatures, as well as daily radiation, under base and future climate conditions. results and discussionaccording to the results, the majority of iran (90.49%) has an arid and semi-arid climate. the percentage of arid climate is 68.82%, while that of semi-arid climate is 21.97%. therefore, iran should be called an arid and semi-arid country in terms of climate. by analysis of the effects of climate change indicates that in future periods, the precipitation and average temperature will increase. this increase will be greater under the rcp8.5 scenario than the rcp2.6 scenario. the study of the climatic classification of iran in the coming periods indicates that the majority of the country will continue to experience arid and semi-arid climates. the sum of arid and semi-arid climates will reach its lowest level in the period of 2020-2041. this is following the rcp2.6 scenario, after which these climates are expected to expand once more. according to the rcp8.5 scenario, during the periods of 2021-2040, 2041-2060, and 2061-2080, the total area of arid and semi-arid climates will decrease. however, from 2081 to 2100, this trend will be reversed, increasing in these climates. according to the results of this research and according to the forecast, although according to different release scenarios, the difference in the area of different classes can be seen, in the future, arid and semi-arid climatic zones will still form the majority of iran. conclusionin this research, by using the latest available data, iran’s climate is classified by the de martonne aridity index, and then the changes in iran’s climate classes under the effects of climate change in the future periods, according to the output of the canesm2 model from the cmip5 modes, which is downscaled using the lars-wg model. it has been investigated according to two emission scenarios, rcp2.6 and rcp8.5. the results indicated that the arid climate with 68.82% and the semi-arid climate with 21.97% constitute the largest area of iran. the remaining climatic classes collectively comprise less than 10% of iran’s area. therefore, iran should be called an arid and semi-arid country in terms of climate. investigating the effects of climate change on precipitation and temperature showed that both precipitation and average temperature will increase in future periods. however, the increase in both variables will be greater under the rcp8.5 scenario. the study of the climatic classification of iran in the coming periods indicates that the majority of the country will continue to experience arid and semi-arid climates. the findings of this study indicate the necessity of addressing the issue of climate change and the importance of involving experts and macro planners in the analysis of the effects of climate change. it is suggested to use the output of other gcm models in future research due to the uncertainty of climate scenarios. also, the use of diverse climate classification methods that incorporate other variables is suggested for more precise identification of climate characteristics