Location of blocking and precipitation in Iran

Document Type : Research Article

Authors

• Narges Naseri ¹
• Reza Doostan ²
• Abbas Mofidi ³

¹ M.A Student of Climatology, Ferdowsi University of Mashhad, Mashhad, Iran

² Assistant Professor of Climatology, Ferdowsi University of Mashhad, Mashhad, Iran

³ Assistant Professor of Climatology, Ferdowsi university of Mashhad, Mashhad, Iran

10.22067/geoeh.2021.67003.0

Abstract

To determine of location and type of blockings affecting the cold climate of Iran, daily geopotential height data of 500 hPa in 10-70 degrees north and 10-80 degrees east with grid point of 2.5 degrees in period of 1961-2010 were used. Blockings were identified by quantitative Tebaldi index on digital points. In the study area, there are three areas of blocking occurrence in Central Europe, Eastern Europe and Central Asia, respectively. The predominant type of blocking in these areas is of the Rex type, with the blocking and the cold storage being placed on top of each other in the middle levels of the atmosphere.  If a Rex block is formed in Central and Eastern Europe, at the same time, a deep or cold trough is formed in Central Asia, and this sequence is normal in meridional atmospheric systems. Iran's precipitation is most closely related to the Eastern European blocking system and the Central Asian cold zone, and precipitation is increasing in most parts of Iran. However, if atmospheric high increases in Central Asia and omega-type blocking is formed, due to the increase in atmospheric altitude, precipitation will decrease in most parts of Iran. But if an omega-type blockage is formed in Central Europe, with the deepening of trough in the Balkans and the Black Sea, it is accompanied by precipitation in northwestern Iran, and if this type of blocking is formed in Eastern Europe, the concentration of precipitation is mainly in the Caspian region, from the Eastern Caspian to the northeast of Iran.

Keywords

• blocking
• Tebaldi index
• precipitation
• Iran

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References

امیدوار، کمال؛ صفرپور، فرشاد؛ محمودآبادی، مهدی؛ الفتی، سعید؛ 1389. تحلیل همدیدی اثرهای سردچال در وقوع بارش‌های شدید در نواحی مرکز و جنوب غربی ایران. مدرس علوم انسانی، برنامه‌ریزی و آمایش فضا. شماره . صص 161-189.

خورشید دوست، علی‌محمد؛ مفیدی، عباس؛ رسولی، علی‌اکبر؛ آزرم، کامل؛ 1395. تحلیل همدیدی سازوکار وقوع بارش‌های سنگین بهاره در شمال غرب ایران. مخاطرات طبیعی. شماره . صص 53-82.

درگاهیان، فاطمه؛ علیجانی، بهلول؛ 1392. بررسی اثر بلاکینگ بر رخداد برف‌های سنگین و مداوم ایران. فصلنامه جغرافیایی سرزمین. شماره 38. صص 1-14.

درگاهیان، فاطمه؛ علیجانی، بهلول؛ محمدی، حسین؛ 1393. آشکارسازی و مطالعه اقلیم‌شناسی رخدادهای بلاکینگ مؤثر بر آب‌وهوای ایران (دوره آماری، 1953-2012) در فصل سرد. فضای جغرافیایی. شماره 48. صص 237-256.

عزیزی، قاسم؛ خلیلی، مائده؛ 1390. نقش بلاکینگ در رخداد سرماهای فرین ایران. پژوهش‌های جغرافیای طبیعی. شماره 77، صص 39-55.

علیجانی، بهلول؛ 1391. اقلیم‌شناسی سینوپتیک. انتشارات سمت.

نیک‌اندیش، نسرین؛ هدایی آرانی، مجتبی؛ 1394. نقش‌آفرینی بندال‌ها در رخداد مخاطرات ژئومورفودینامیکی (مطالعه موردی زمین‌لغزش‌های فروردین 1377 غرب چهارمحال بختیاری). جغرافیا و برنامه‌ریزی محیطی. شماره 3. صص 192-171.

 

Feudale L, Shukla J., 2011. Influence of sea surface temperature on the European heat wave of 2003 summer. Part I: an observational study. Climate dynamics, 36: 1691-1703.

Luo D, Yao Y, Dai A, Feldstein SB., 2015. The positive North Atlantic Oscillation with downstream blocking and Middle East snowstorms: the large-scale environment. Journal of Climate, 28: 6398-6418.

Masoompour Samakosh J, Soltani M, Hanafi A, Azizi GH, Mirzaei E, Ranjbar SaadatAbadi A,Yousefi Y. 2014. The omega blocking condition and extreme rainfall in Northwestern Iran during 25-28 October 2008. Earth and Space Physics, 40: 55-74.

Pavan V. Molteni F. Brankovic C., 2000. Wintertime variability in the Euro‐Atlantic region in observations and in ECMWF seasonal ensemble experiments. Quarterly Journal of the Royal Meteorological Society, 126: 2143-2173.

Porter G., 2017.Identifying precursors to winter time Atlantic Blocking Events. Department of Atmospheric and Oceanic Sciences, University of Maryland, 1-51. 

Rex DF. 1950., Blocking action in the middle troposphere and its effect upon regional climate. Tellus, 2: 275-301.

Silva WL, Nascimento MX, Menezes WF., 2015. Atmospheric blocking in the South Atlantic during the summer 2014: a synoptic analysis of the phenomenon. Atmospheric and Climate Sciences, 5: 386-393.

Tibaldi S. Molteni F.,1990.On the operational predictability of blocking. Tellus, 42: 343-365.

Wang L, Chen W, Zhou W, Chan J.C, Barrio Pedro D, Huang R., 2010. Effect of the climate shift around mid-1970s on the relationship between wintertime Ural blocking circulation and East Asian climate. International Journal of Climatology, 30: 153-158.

Wiedenmann JM, Lupo AR, Mokhov II, Tikhonova EA., 2002. The Climatology of Blocking Anticyclones for the Northern and Southern Hemispheres: Block Intensity as a Diagnostic. Journal of Climate, 15:3459-3473.