بررسی تغییرات آب معادل برف، عمق برف و چگالی برف در ایران با استفاده از داده‌های بازتحلیل ERA5-Land

مقالات آماده انتشار

نوع مقاله : مقاله پژوهشی

نویسندگان

سمیه حاجیوند پایداری

محمد سلیقه

بهلول علیجانی

علیرضا کربلایی

گروه جغرافیای طبیعی، دانشکده علوم جغرافیایی، دانشگاه خوارزمی، تهران، ایران

10.22067/geoeh.2026.100091.1688

چکیده

آب معادل برف، عمق برف و چگالی برف سه متغیر بنیادین هیدرولوژی برف هستند، اما بررسی هم‌زمان و سراسری هر سه متغیر در ایران به‌ندرت انجام شده است. پژوهش حاضر تغییرات مکانی-زمانی این سه متغیر را با داده‌های ماهانه ERA5-Land با تفکیک 0.1 درجه طی دوره ۱۹۸۰ تا ۲۰۲۴ در ۱۵۵۴۷ یاخته خشکی بررسی کرد. روابط دومتغیره با نمودارهای پراکنش، رگرسیون و ضرایب پیرسون و اسپیرمن در چهار نوع نمونه و با در نظر گرفتن وابستگی تعریفی SWE = SD × ρs/1000 ارزیابی شد. سپس تحلیل مؤلفه‌های اصلی و خوشه‌بندی K-means اجرا و تعداد خوشه‌ها با معیارهای آرنج، سیلوئت و کالینسکی-هاراباز و یک آزمون حساسیت دومتغیره سنجیده شد. روند و نقطه تغییر سری‌های میانگین مکانی با آزمون‌های من-کندال اصلاح‌شده، شیب سن و پتیت و الگوی مکانی تغییرات با نقشه‌های روند یاخته‌ای و نقشه‌های اختلاف دو دوره بررسی شد. نتایج نشان داد ذخیره برف به‌شدت متمرکز است؛ تنها 27.3 درصد مساحت کشور میانگین بلندمدت SWE بیش از یک میلی‌متر دارد، نیمی از ذخیره در 3.7 درصد مساحت قرار دارد (ضریب جینی 0.87) و بیشینه آن (0.155 متر معادل آب) در زردکوه-دنا دیده می‌شود. عمق و SWE تقریباً هم‌خط‌اند (r = ۰/۹۹) که بخشی از آن ساختاری است، در حالی که رابطه چگالی با عمق مثبت و غیرخطی است و ضرایب آن به نوع نمونه وابسته است (0.62 تا 0.87). مؤلفه اول 8/90 درصد واریانس را تبیین کرد و چهار طبقه برفی در امتداد یک گرادیان پیوسته تفکیک شد؛ طبقه برف‌انبار کوهستانی با 2/1 درصد مساحت، 8/25درصد ذخیره را در بر دارد. میانگین SWE دسامبر تا مارس روند کاهشی معنادار داشت (Z = −۳/۷۳؛ شیب سن 9/1-میلی‌متر در دهه) و پس از ۲۰۰۸ به حدود نصف رسید؛ کاهش آوریل معنادار و تغییر نوامبر نامعنادار بود. کاهش معنادار SWE زمستانه 3/80 درصد پهنه برف‌گیر را در بر می‌گیرد.

کلیدواژه‌ها

آب معادل برف

عمق برف

چگالی برف

ERA5-Land

تحلیل روند

موضوعات

• تغییر اقلیم

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©2026 The author(s). This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0)

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