Synoptic Analysis of Blockings Causing Heavy and Continuous Rains in Iran

Document Type : مقاله پژوهشی

Authors

• Fatemeh Dargahian ¹
• Bohlul Alijani ²
• Hossein Mohammadi ³

¹ Islamic Azad University, Tehran

² Kharazmi University, Tehran

³ Tehran University

10.22067/geo.v3i2.26653

Abstract

1. Introduction
The effect of blocking on Iran’s precipitation in numeral way and long-term has not been done yet. However, in some researches based on weak indexes like one-dimension has been implied to Iran that in studying many cases we observe lack of blocking event and or their continuation that has been for less than 5 days. This phenomenon in some cases occurs in our country directly and most of its parts are under its predominance, but according to its placement in proximity of zone, its maximum in the world, Atlantic-Europe zone is influenced by its effects repeatedly and probably may be affected more by recent cases. Given the fact that in each zone, precipitation is considered as a permanent development base, therefore the knowledge of effective models on it has an extraordinary importance in order to predict and knowing from them. On the other hand, with respect to this that most studies have been carried out in sample way, the knowledge of these patterns can have a high carefulness and accuracy in quantity way.
2. Study Area
In order to investigate the blocking systems affecting the climate of Iran, at first the study area was chosen in the within the 0– 90N and 90W – 100E. At the second stage the origin and location of the blocking systems were determined and study area was decreased to the 20N – 80N and 40W – 100E in order to study only those systems in close contact with the climate of Iran. In order to better understand the effect of blocking patterns of precipitation and temperature the study area was limited to Iran.
3. Material and Methods
Data related to geo-potential height of 500 hPa level in regard to two dimensions index of visible blocking, daily for cold season in year for a 65-year period from 1953 to 2012 in a 2/5 *2/5 network that is appropriate for studying the large-scale occurrences like the blocking was extracted from site NCEP-NCAR for an area between 0 to 90N latitudes and 90W to100E longitudes. Then the investigated zone was bounded according to the knowledge of the limit and the origin of the effective blocking on Iran’ weather from 40 W to 100 E longitude Using a quantity way of two-dimensional revelation and synoptic filters along with it, all blocking events were revealed. The effective happenings on rainfall were separated then these events with use of a factor analysis way were analyzed and based on classification way of K-means were categorized and finally the blocking prevailing events that are effective on Iran’s precipitation were identified. Four prevailing patterns for rainfall were extracted that the first two models, the precipitation pattern resulted from the left and right half were totally considered as omega kind model. Two other models were including dipole and Rex Patterns of blocking. Synoptic conditions of above levels of atmosphere and ground level were analyzed for each pattern
4. Results and Discussion
In omega pattern, right trough of Iran is located in front of the trough. Lifetime duration of this blocking from forming until puberty and death has been in total the days and the system with regard to the feature of its being quasi-stationary, has had a moving toward east with a very low speed and this matter has been caused that Iran’s different parts from west to east is located respectively in front of trough and under trough axis several continuous days and have instable conditions and necessary rise for raining. In omega model, left trough of west and western north is situated in front of the left trough and conditions for instability and continuous precipitation has been ready and in most stations in addition to the permanence of rainfall for several days, it was also shown heavy rainfall. In dipole pattern of west and western north, the country is located in front of below low-rise trough and conditions are appropriate for rising, instability and continuous and heavy precipitation. In Rex Pattern, ridge is placed in high latitudes and trough is situated in lower latitudes and Iran is influenced by in front of below trough. In this model, in Iran’s western half, conditions are available for constant and heavy precipitation
5. Conclusion
Blocking is one of the atmospheric large-scale phenomenon which have numerous synoptic phenomenon synoptic scales. The effective blockings on Iran’s weather among atmospheric parameters have the most effect on rainfall. Blocking event in some cases can on account of severity and continuous precipitation in a zone lead to flood and damage, therefore the knowledge of its synoptic prevailing pattern in order to predict and issuing the necessary per-awareness’s and taking the essential measures in the affected area in terms of risk management have considerable importance. Among the blocking patterns leaded to rainfall, the omega model has more abundance than other models. In omega pattern, two marginal troughs on ground level have a low pressure and under and in front of trough, conditions for raining are available. In terms of the continuity of more precipitation, the omega model can has more permanence and other kinds have less severity and permanence. Statistical survey of the precipitations resulted from blocking showed that blocking can lead to continual and severe rainfalls, but every continual and severe rainfall is not resulted from blocking.

Keywords

• blocking
• synoptic patterns
• heavy and continuous rains

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References

آزاد، روح الله؛ 1386. مطالعه دینامیکی و اقلیم‌شناختی پدیده بلاکینگ بر روی منطقه اروپا-آسیا. پایان‌نامه کارشناسی ارشد هواشناسی. موسسه ژئوفیزیک دانشگاه تهران.

احمدی حجت، معصومه؛ احمدی گیوی، فرهنگ؛1391. مطالعه وقوع بلاکینگ در مرحله تقویت پرفشار سیبری. مجموع مقالات پانزدهمین کنفرانس ژئوفیزیک ایران. 28-26 اردیبهشت.

براتی، غلامرضا؛ بداق جمالی، جواد؛ ملکی، ناصر؛ 1391. نقش واچرخندها در رخداد بارش‌های سنگین دهه اخیر غرب ایران. پژوهش‌های جغرافیای طبیعی. شماره80. صص85-98.

حبیبی، فریده؛ 1386. نقش سامانه بندالی در چرخندزایی روی شرق دریای مدیترانه و بررسی نقش آن در سیل روی منطقه غرب ایران. پژوهش‌های جغرافیایی. شماره 62. صص127-109.

عزیزی، قاسم؛ 1375. بلوکینگ و اثرات آن بر بارش ایران. رساله دکتری. دانشگاه تربیت مدرس.

عزیزی، قاسم؛ شمسی پور، علی اکبر؛ میری، مرتضی؛1391. واکاوی همدیدی ارتباط آتش‌سوزی‌های ماه ژوئیه 2010 روسیه و سیل پاکستان. جغرافیا و توسعه. شماره 29. صص144-131.

عزیزی، قاسم؛ نبوی، سیدامیر. آ؛ میری، مرتضی؛1391. داده‌کاوی گردش‌های جوی برای بررسی نقش الگوهای بندالی در ایجاد بارش‌های شمال شرق ایران. پژوهش‌های جغرافیای طبیعی. شماره 81. صص 136- 109.

مفیدی، عباس؛ حسین زاده، سید رضا؛ محمدیاریان، محترم؛1392. جغرافیا و مخاطرات محیطی. شماره 26. صص16-1.

مؤمن پور، فروغ؛ 1390، بررسی موردی اثر بلاکینگ بر روی جبهه‌زایی سطوح زیرین جو در خاورمیانه و اروپا. پایان‌نامه کارشناسی ارشد هواشناسی. دانشگاه علوم و تحقیقات تهران.

Ahmadi, H., Ahmadi,Givi, F., 2012. Study occurrence of blocking in Strengthened Siberian high-pressure phase. Fifteenth Conference articles Iran Geophysics.

Azad, R., 2007. Dynamics and climatology of blocking effect on the Europe – Asia blocking, MS Thesis, Tehran University Geophysics Institute.

Azizi, G., Shamsi poor, A., Miri, M., 2012. Synoptic analysis related fires in Russia and

Floods in Pkistan July 2010. Geography and Development 29, 144-131.

Azizi, G., Nabavi, O., Miri, M., 2012. Atmospheric circulation data mining to explore the role of precipitation patterns in the creation of bandali North East Iran. Geography Research 81, 109-126.

Azizi, G., 1996. Blocking its effects on precipitation in Iran, Ph.D Dissertation, University of Tarbeit Modaress.

Azizi, G., Khalili, M., 2012. An investigation of Iran’s precipitation anomalies in relation with atmospheric blocking, Advances in Meteorology, Climatology and Atmospheric Physics Springer Atmospheric Sciences 2013, 521-526.

Barati, G., Bedaki Jamali, J., Maleki, N., 2012. The anticyclone in the event of heavy rainfall in recent decades, West Persia. Physical Geography Research 80, 85-89.

Barriopedro, D. R., Garcı´a-Herrera, A. R., 2006. Climatology of northern hemisphere blocking. Journal of Climate 19, 1042–10.

Bernd ,S., Richard ,B., Klaus ,F., 2011. Blocking detection based on synoptic filters. Advances in Meteorology 20, 1 -11.

Chris, W,. Hylke, V., Reindert J., 2012. On the direction of Rossby wave breaking in blocking. Climate Dynamics 39, 2823-2831.

Croci-Maspoli, M., Schwierz, C., Davies, H. C., 2007. A multifaceted climatology of

atmospheric blocking and its recent linear trend. Journal of Climate 20, 633–649.

Davini, P., Cagnazzo, C., Gualdi, S., and Navarra, A., 2012. Bidimensional diagnostics,

variability and trends of Northern Hemisphere Blocking . Journal of Climate 25, 6496–6509.

Etienne D.S., Seok W.S., and Hai, L., 2013. Evaluation of northern hemisphere blocking climatology in the global environment multiscale model. Monthiy Weather Review 141, 707–727.

Elizabeth A. Barnes, J.S., Tim ,W., 2011. A methodology for the comparison of blocking climatologies across indices, models and climate scenarios. Climate Dynamics 38, 2467-2481.

Habibi, F., 2007. The Role of Blocking in the Cyclogenesis of East Mediterranean and Examine its role in Flooding the area West of Iran, Geographical Research 62, 127-109.

Hughes, M., Alex, H., Robert, G., 2009. Blocking in Areas of Complex Topography and Its Influence on Rainfall Distribution. Journal of Atmospheric Science 66, 508–518.

Lu, M. M., Chih,P. C., 2009. Unusual late-season cold surges during the 2005

Asian Winter Monsoon Roles of Atlantic Blocking and the Central Asian Anticyclone Journal of Climate, 22 , 5205–5217.

Pook,M., Risbey, J., McIntosh , P., 2011. East coast lows, atmospheric blocking and Rainfall. Tasmanian perspective, 17th national conference of the Australian Meteorological and Oceanographic Society.

Momenpoor, F., 2011. A case study of the influence of the blocking on the low-leve front genesis in Europe and Middle East region, MS Thesis in weather, Science and Research Branch of Tehran.

Mofidi, A., Hosseinzadeh, S.R., Mohammadyariyan, M., 2013. Atmospheric hazard zonation in the North East of Iran, Geography and Environmental Hazards 6, 1-16.

Rimbu, N., Lohmann, G., 2011. Winter and summer blocking variability in the North

Atlantic region evidence from long-term observational and proxy data from southwestern Greenland. Climate of the Past 7, 543–555.

Renwick, J. A., Wallace, J. M., 1996. Relationships between North Pacific Winter time blocking, El Nino, and the PNA pattern. Monthiy Weather Review 124, 2071-2076.

Rimbu, N., Lohmann, G., Grosfeld, K., 2007. Blocking signature in ice core records from northern Greenland. Geophysical Research Letters 34, L09704.

Scaife, A.A., Woollings, T., Knight, J., Martin, G., Hinton, T., 2010. Atmospheric Blocking and Mean Biases in Climate Models. Journal of Climate 23, 6143–6152.

Scherrer, S. C., Croci-Maspoli, M., Schwierz, C., and Appenzeller, C., 2006. Two-dimensional indices of atmospheric blocking and their statistical relationship with winter climate patterns in the Euro-Atlantic region. Journal of Climate 26, 233–249.

Shabbar, A., Huang, J., and Higuchi, K., 2001. The relationship between the wintertime North Atlantic Oscillation and blocking episodes in the North Atlantic. Journal of Climate 21, 355–369.

Shabrang, L., 2012. Blocking effect of cyclogenesis Mediterranean, Fourteenth Iranian Geophysical Conference.

Thando, N., Darryn, W., 2011. A Climatology of Rossby Wave breaking on the Southern Hemisphere Tropopause. Journal of the Atmospheric Sciences 68, 798-811.

Tibaldi, S., E. Tosi, A. Navarra, L. P., 1994. Northern and Southern Hemisphere Seasonal Variability of Blocking Frequency and Predictability. Monthiy Weather Review 22, 1971–2003.

Wiedenmann, J. M., Lupo, A R., 2002. The Climatology of Blocking Anticyclones for the Northern and Southern Hemispheres Journal of Climate 15, 3459–3473.