مجله ژئوفیزیک ایران

مجله ژئوفیزیک ایران

تغییرات روزها و شب‌های سرد و گرم در ایران با استفاده پیکربندی‌های همادی چند مدلی EC-Earth3

مقالات آماده انتشار

نوع مقاله : مقاله پژوهشی‌

نویسنده
عباسعلی داداشی رودباری
استادیار اقلیم شناسی، گروه جغرافیا، دانشکده ادبیات و علوم انسانی، دانشگاه فردوسی مشهد، مشهد، ایران
10.30499/ijg.2026.569942.1749
چکیده
تغییر اقلیم به‌طور فزاینده‌ای فراوانی و شدت رخدادهای فرین دمایی را تحت‌تأثیر قرار داده است. پژوهش حاضر با هدف بررسی این مخاطرات در ایران، تغییرات چهار شاخص فرین TX90p، TN90p، Tx10p و TN10p را بر اساس پنج پیکربندی اصلی مدل سامانه زمین ماژولار EC-Earth3 و تحت چهار سناریوی SSPs مورد ارزیابی قرار داده است. ابتدا یک چند مدلی همادی از پنج پیکربندی مدل EC-Earth3 تولید شد. نتایج نشان داد چندمدلی همادی (MME) با کاهش خطاهای مدل‌های منفرد، کارایی بالاتری ارائه داده است. نتایج تحقیق نشان دهنده یک ناهمگونی شدید در الگوی تغییرات فرین‌های دمایی است؛ به‌طوری‌که کاهش معنی‌دار در فراوانی روزها و شب‌های سرد با افزایش در رخدادهای گرم در ایران همراه شده است. تحت سناریوی SSP5-8.5، شاخص روزهای گرم (TX90p) در مناطق داخلی و کویری ایران تا پایان قرن حاضر به بیش از ۶۵ درصد خواهد رسید که نشان‌دهنده تغییر ماهیت اقلیمی این مناطق است. کانون‌های اصلی تغییرات فرین‌های دمایی عمدتاً بر مناطق مرکزی، دشت لوت و جنوب‌شرق کشور منطبق هستند. در این مناطق بازخوردهای مثبت ناشی از کسری رطوبت خاک موجب تشدید امواج گرمایی و روند افزایشی تبخیر می‌شود. در مقابل، مناطق شمالی و ارتفاعات البرز، اگرچه روند افزایشی دارند، اما به دلیل اثرات تعدیل‌کننده توپوگرافی و رطوبتی، آهنگ تغییرات کمتری را تجربه می‌کنند. همچنین، واگرایی شدید بین سناریوی SSP1-2.6 و SSP5-8.5 در نیمه دوم قرن، بر نقش حیاتی سیاست‌های کاهش انتشار در کنترل شدت تغییرات فرین‌های تأکید دارد.
 
کلیدواژه‌ها
تغییر اقلیم
CMIP6
فرین دمایی
سناریوهای SSP
ایران

موضوعات

عنوان مقاله English

Changes in cold and hot days and nights indices in Iran using EC-Earth3 multi-model ensemble configurations

نویسنده English

Abbasali Dadashi-Roudbari
Assistant Professor, Department of Geography, Faculty of Letters and Humanities, Ferdowsi University of Mashhad, Mashhad, Iran
چکیده English

Global risk assessments underscore a critical paradigm shift: climate change has evolved from a distant potentiality into an immediate and destructive certainty. Accordingly, the Global Risks Report (2025) classifies extreme climate events as the second most severe risk within the short-term horizon. By highlighting a transition from a warning phase to an active crisis, the report elucidates that the nonlinear intensification of phenomena such as flash floods, heatwaves, and storms has surpassed normal atmospheric variability, inflicting structural damage upon critical ecosystems and economic infrastructure. Since climate change increasingly dictates the frequency and intensity of temperature extremes, the present study evaluates these hazards within the context of Iran. We examined variations in four extreme indices—TX90p, TN90p, TX10p, and TN10p—utilizing five primary configurations of the EC-Earth3 modular Earth system model across four Shared Socioeconomic Pathways (SSPs).
    Initially, a Multi-Model Ensemble (MME) was generated from the five EC-Earth3 configurations. The analysis demonstrated that the MME provided superior performance by mitigating the errors inherent in individual models. Findings reveal a pronounced heterogeneity in the changing patterns of temperature extremes; specifically, a significant decline in the frequency of cold days and nights runs parallel to a surge in warm events across the country. Under the SSP5-8.5 scenario, the warm days index (TX90p) in Iran’s internal and desert regions is projected to exceed 65% by the end of the century, signaling a fundamental transformation in the climate of these areas. The primary hotspots of these warm extremes align largely with the central regions, the Dasht-e Lut, and the southeast. In these zones, positive feedbacks driven by soil moisture deficits appear to exacerbate heatwaves and accelerate evaporation trends. Conversely, northern regions and the Alborz highlands, while still exhibiting an upward trend, experience a more gradual rate of change due to the moderating influences of topography and moisture availability.
    Furthermore, the stark divergence between scenarios SSP1-2.6 and SSP5-8.5 during the latter half of the century underscores the critical imperative of emission reduction policies in curbing the severity of extreme fluctuations. Thermodynamic land-atmosphere feedbacks are poised to play an increasingly dominant role in amplifying future temperature extremes in Iran. Given the country’s arid and semi-arid climate, soil moisture depletion acts as a critical limiting factor. Under conditions of soil moisture scarcity, the contribution of latent heat flux (evaporative cooling) diminishes, shifting the energy balance in favor of sensible heat flux; this mechanism directly drives an increase in air temperatures. This positive feedback loop particularly under high-emission scenarios (SSP5-8.5) associated with intensified aridification may precipitate ultra-severe warm extremes characterized by a synergy of heat accumulation and profound surface desiccation.

کلیدواژه‌ها English

Climate change
CMIP6
Temperature extremes
SSP scenarios
Iran
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مجله ژئوفیزیک ایران

مقالات آماده انتشار، پذیرفته شده
انتشار آنلاین از 02 فروردین 1405