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پژوهش های جغرافیای طبیعی، جلد ۵۰، شماره ۴، صفحات ۶۳۹-۶۵۳
عنوان فارسی اثر کوه‌های زاگرس بر چرخندهای بارش‌زای ایران
چکیده فارسی مقاله در این پژوهش برای شناخت تأثیر رشته‏کوه زاگرس در تغییرات چرخند‏هایی که از غرب وارد ایران می‏شوند از رویکرد محیطی به گردشی استفاده شد. بدین منظور، داده‏های سیزده ایستگاه سینوپتیک غرب ایران و داده‏های ساعتی ERA-Interim با تفکیک مکانی 125/0×125/0 درجه، طی سال‏های 1984ـ 2013 دریافت شد. با این رویکرد، 203 روز بارش فراگیر شناسایی شد. با اعمال تکنیک تحلیل عاملی بر روی داده‏های تراز دریای متناظر با این روزها، عامل دوم بیشترین پراش بارش‏های حاصل از چرخند را توجیه می‏کند. روزهای چهاردهم تا هجدهم آپریل 2003، که بیشترین همبستگی را با سایر روزهای این عامل دارد، الگوی نماینده انتخاب شد. در این الگو، چرخندِ‏ِ رسیده به کوه‏های زاگرس از زمان شکل‏گیری تا زمان رسیدن بر روی عراق و ادغام با سامانۀ سودانی، به لحاظ دینامیکی، تقویت می‏شود. به هنگام نزدیک‏شدن به زاگرس، از تاوایی مثبت و سرعت قائم هوا کاسته می‏شود؛ اما با عبور از زاگرس بر تاوایی مثبت آن افزوده می‏شود. رابطه چرخند تقویت‏شده با منطقه واگرایی ترازهای میانی وردسپهر در همه مراحل مشاهده شد. زاگرس نخست باعث تضعیف و دوقطبی‏شدن چرخند می‏شود. سپس، با دور شدن از کوهستان، چرخند مجدداً تقویت می‏شود. این چرخند‏ها را چرخند‏ زاگرسی می‏توان نامید.
کلیدواژه‌های فارسی مقاله تاوایی، چرخندهای بادپناهی، زاگرس، سرعت قائم هوا، شار رطوبت،
عنوان انگلیسی The Effect of Zagros Mountains on Iran's Rainfall cyclones
چکیده انگلیسی مقاله Introduction The activity of synoptic cyclones plays an important role in determining the local climate and the formation of large-scale atmospheric circulation through the vertical and horizontal exchange of heat, humidity and momentum, coupled with interaction with large scale circulation centers (Zhu et al, 2001: 1523). The cyclones generally are transmitter the bad weather conditions and also represent the initial mechanism of transmitter moisture and heat to the pole. Systematic changes in geographical location or the intensity / frequency of cyclone activity will have significant disparities among other regional climate impacts (Wang, 2006: 3145). The effect of mountainous obstacles on synoptic systems, especially the cyclone systems, has known. The mountain range is one of the factors, In addition to disrupting the face of the earth's uniformity, also disrupt the climatic uniformity. The purpose of this study is to determine the effect of thermodynamics of Zagros Mountain on the changes in cyclones entering the country from the west. Materials and methods, For this purpose, the daily precipitation data of 13 stations of the Meteorological Organization in West of Iran were received. Also geopotential data were extracted from the NCEP / NCAR databases with spatial resolution of 2.5 × 2.5 degrees and ERA-Interim data from ECMWF databases with spatial resolution of 0.125 × 0.125 degrees, thier framework is 0 to 80 degrees east and 0 to 60 degrees north. Using the Factor Analysis method, April 14th-18th, 2003 was selected as the best pattern. After selecting the sample day, sea level pressure maps and geopotential heights of different levels were prepared and analyzed. Results and discussion The result of the study of these maps showed that the cyclone reaching the Zagros Mountains, dynamically strengthened from the day it formed until it arrived in Iraq. When approaching the Zagros, the vorticity and its omega are reduced, but crossing Zagros, a positive vorticity increase happens. These types of cyclones call Zagros cyclones. The relationship between the amplified cyclone with the divergence region of the middle and middle levels were observed at all stages. The Zagros roughness, like a wall, initially causes the cyclone reached with Iran to weaken and become bipolar. But the passage of the cyclones from it, the thermodynamic conditions of the descending air in the lee mountain range, that makes them revival. As the roughness collides, a weak core remains in the Zagros range, and another nucleus is formed by passing through the mountains in the central regions of the country, and is reinforced in the next hours; and finally, the cyclone is amplified and it leaves Iran completely. These cyclones can be called zagros second cyclones. Conclusion Mountain barriers consider as the factors destroying the homogeneity of the local climate. Sometimes they act as the planets like the Rocky Mountains. Iran's land are heterogeneous due to elevations in the north, west, and other areas, Iran is heterogeneous in term of geomorphology and climatology. One of the most outstanding effects of roughness on the climate is the change in the structure of systems passing through these barriers. Zagros Mountains is one of the main mountain ranges of Iran, with an almost northwest-southeast direction with a maximum height of about 4,400 meters zardkuh, has a significant impact on immigrant systems in the country. A study on the cyclone on April 14th , 2003 showed that this cyclone was formed on the April 12th on the northwest of Europe, moving towards the Mediterranean Sea. its trough arrives in the country on the April 14th and it reaches the slopes of Zagros on the 16th. As Zagros is approaching, changes in pressure in the back and the lee of Zagros are increasing. Vorticity and divergences are completely different in two parts. In the altitudinal areas in the Zagros line, during a few days and during the passage of the cyclone, there is a negative vorticity. The vertical velocity also demonstrates subsidence in Zagros altitudinal areas. The results vividly prove that the cyclone is(get) weakened in collisions with the Zagros, and its movement gets slowness(slow), but it does not disappear. But also it is re-reinforced on the Zagros lee in the central of regions, and continued its route to outside the borders of the country. Keywords: Lee cyclones, cyclonic vorticity, Vertical Velocity, humidity flux, Zagros
کلیدواژه‌های انگلیسی مقاله
نویسندگان مقاله فاطمه ستوده |
دانشجوی دکتری آب و هواشناسی سینوپتیک، دانشکدة جغرافیا، دانشگاه خوارزمی تهران

بهلول علیجانی |
استاد گروه آب و هواشناسی، دانشکدة جغرافیا، دانشگاه خوارزمی تهران

محمد سلیقه |
دانشیار گروه آب و هواشناسی، دانشکدة جغرافیا، دانشگاه خوارزمی تهران

مهری اکبری |
استادیار گروه آب و هواشناسی، دانشکدة جغرافیا، دانشگاه خوارزمی تهران

نشانی اینترنتی https://jphgr.ut.ac.ir/article_70313_38c6432ae877fbc230037901a7c0d46a.pdf
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