Synoptic Analysis of Extreme and Widespread Precipitations in Caspian Eastern Coasts

Document Type : مقاله پژوهشی


University of Payame- Noor


. Introduction
Since precipitation and its changes in each geographical area and also east coasts of the Caspian Sea make changes in human life and human activities directly or indirectly, this study wants to determine synoptic and dynamic patterns during precipitations and also appoint the resource of extreme and widespread precipitations in east coasts of Caspian. In this line, much research has been done in Iran and around the world. In the case of research done outside Iran, one can mention Lana&Borghino (2000), Huos et al (2008), Federico et al (2008), Keables (1989), and Lorenz et al (2008). In Iran, we can nameLashkary (1996), NajarSaligheh (2001), Khoshhal (1997), Mohammadi (2012), Bagheri (1993), Hosseini (2009), Azizi and Samadi (2007), Mofidiet, Zarrin and Janbaz Ghobadi (2008), and RezaiBanafshehet, Najafi, Naghizadeh and Abkharabat (2015).
2. Material and Methods
In this research, for synoptic analysis of extreme and widespread precipitations in Caspian eastern coasts, we interpolated and traced the daily Isohyet maps from 1340.1.1 to 1383.11.10 (15992 days) on the 14*14 km pixels by Kriging method and by use of daily precipitation data base of this region. These data provided the information of 108 studied local points for 15992 days to calculate maximum precipitation and area percentage under precipitation for every precipitation day. On this basis, we identified the most extreme and the most widespread of region precipitations on the basis of 99th centile base index for studying and analyzing. By applying environment – circulation approach and agglomerative hierarchical cluster analysis by "ward" method on the maps of sea level pressure, maps of the atmosphere thickness at levels of 500 and 1000 hPa and maps 500 hPa circulation patterns, circulation patterns which were effective and important for creating the extreme and widespread precipitations of Caspian eastern coasts. In continuation, for analyzing the precipitations in every pattern, the representative day defined on the basis of correlation coefficient with 95% threshold and in these days, sea level pressure maps, atmosphere thickness in 500-1000 hPalevels, 500 hPa circulation patterns, functions of frontogenesis for 500 and 1000 hPa levels and moisture convergence flux for 925 and 1000 hPa levels were traced and analyzed.
3. Results and Discussion
The results of this research in the five patterns of sea level pressure indicate the presence of high pressure on the Black Sea that it’s tongue have been extended to Caspian coasts. Atmosphere thickness patterns indicate the deep trough on the Caspian Sea and Black Sea too. The analysis of frontogenesis function maps illustrate the existence of front on high latitude and Siberia that have had effect on studied area. The analysis of moisture convergence flux indicate that Caspian Sea is the most important source to providing humidity for precipitation in eastern coasts of this sea, and Aral Lake and Black Sea are in the next importance degree. Of course, mostly, the atmospheric flows importing the humidity of these two source in to the Caspian Sea that higher reinforcement results in occurring the extreme precipitation in eastern coasts of this.
4. Conclusion
The analysis of sea level pressure maps in extreme and widespread precipitations days, shows five patterns. In these patterns we can see depressure condition with high pressure dominance in the north of Iran and low pressure dominance in the south of Iran. Although frequency of the 5th pattern in more than others, the maximum of precipitation is seen in pattern number 2. The precipitations of the region begin from Ordibehesht and continue until Dey. The temporal peaks of precipitation are in Mehr, Aban, Shahryvar, and Azar. The patterns that are drawn, show high pressure systems on east-north of Iran and the Black Sea in all patterns, which enters cold air to the Caspian Sea from Siberia and Europe, and with the humidity of the sea, enters them into east coasts of the Caspian Sea. Atmosphere thickness patterns that are drawn for representative days, indicate the deep trough on the eastern Mediterranean and north west of Caspian Sea, which makes situation for falling cold air from Europe into the area. The analysis of moisture convergence flux shows the importance of the Caspian, Black and Mediterranean Seas as resource of humidity for extreme and widespread precipitations.


باقری، سعید؛ 1372. بررسی سینوپتیکی سیستم‌های سیل‌زا در شمال ایران. پایان نامه کارشناسی ارشد هواشناسی. موسسه ژئوفیزیک. دانشگاه تهران.
جانباز قبادی، غلامرضا؛ مفیدی، عباس؛ زرین، آذر؛ 1390. شناسایی الگوهای همدید بارش‌های شدید زمستانه در سواحل جنوبی دریای خزر. جغرافیا و برنامه ریزی محیطی. شماره 42، صص 40-23.
حسینی، سید محمد؛ 1388. شناسایی شرایط همدید همراه با بارش در پهنۀ نیمه پربارش خزری، پایان نامه دوره کارشناسی ارشد اقلیم شناسی. دانشگاه اصفهان.
خوشحال دستجردی، جواد؛ 1376. تحلیل و ارائه یک مدل سینوپتیک- کلیماتولوژی برای بارشهای بیش از صد میلی‌متر در سواحل جنوبی دریای خزر. رساله دوره دکتری اقلیم شناسی. دانشگاه تربیت مدرس.
رضایی بنفشه، مجید؛ نجفی، محمد سعید؛ نقی‌زاده، حبیبه؛ آب خرابات، شعیب؛ 1394. واکاوی رفتار بارش‌های حدی در ارتباط با عوامل مؤثر بر بارش در غرب و شمال‌غرب. جغرافیا و مخاطرات محیطی. شماره 13، صص 153-133.
عزیزی، قاسم؛ صمدی، زهرا؛ 1386. تحلیل الگوی سینوپتیکی سیل 28 مهرماه 1382 استان‌های گیلان و مازندران. پژوهش‌های جغرافیای. شماره 60، صص 74-61.
علیجانی، بهلول؛ 1385. اقلیم شناسی سینوپتیک. تهران: انتشارات سمت.
لشکری، حسن؛ 1375. الگوی سینوپتیکی بارش‌های شدید جنوب‌غرب ایران. پایان نامه دکتری آب و هواشناسی، دانشگاه تربیت مدرس.
محمدی، بختیار؛ مسعودیان، ابوالفضل؛ 1389. تحلیل همدید بارش‌های سنگین ایران. جغرافیا و توسعه. شماره 19، صص 70-47.
مسعودیان، سید ابوالفضل؛ 1390. آب و هوای ایران. مشهد: انتشارات شریعه توس.
مفیدی، عباس؛ زرین، آذر؛ 1384. بررسی سینوپتیکی تأثیر سامانه‌های کم فشار سودانی در وقوع بارش‌های سیل‌زا در ایران. تحقیقات جغرافیایی، شماره 77، صص 136-113.
مفیدی، عباس؛ زرین، آذر؛ جانباز قبادی، غلامرضا؛1387. تعیین الگوی همدیدی بارش‌های شدید زمستانه و مقایسه آن با الگوی بارش‌های شدید پاییزه در سواحل جنوبی دریای خزر، اولین کنفرانس بین‌المللی تغییرات زیست محیطی منطقه خزری، 3 تا 4 شهریورماه 1387، دانشگاه مازندران، بابلسر.
نجارسلیقه، محمد؛ 1380. الگوهای سینوپتیکی بارش‌های تابستانۀ جنوب ایران. تحقیقات جغرافیایی، شماره 62، صص 125-114.
Alijani, B., 1981. Synoptic origin of precipitation in Iran. Ph.D. Dissertation, Michigan State University East- Lansing, U.S.A.
Alijani, B., 2006. Synoptic climatology, Tehran: Samt Press.
Azizi, G., & Samadi, Z., 2007. Synoptic pattern analysis of 28th october 2003 flood on the Gilan and Mazandaran province. Geography Research Quarterly, 60, 61-74.
Bagheri, S., 1993. Synoptic study of flood generating systems in north of Iran. M.A in meteorology, Geo-physic Institution, Tehran University.
Banacos. P. G., & Schultz, D. M., 2004. Moisture flux convective initiation forecasting.
Carla Lima, K., Satyamurty, P. & Reyes Fernandez, J. P., 2009. Large-scale atmospheric conditions associated with heavy rainfall episodes in southeast Brazil. Theoretical and Applied Climatology، Springer Wien، DOI. 10.1007/s00704-009-0207-9.
Federico, S., Avolio, E., Pasqualoni, L., & Bellecci, C., 2008. Atmospheric patterns for heavy rain events in Calabria. Nat. Hazards Earth Syst. Sci., 8, 1173-1186.
Hidalgo-Munoz, J. M., Argüeso, D., Gamiz-Fortis, S. R., Esteban-Parra, M. J., & Castro-Diez, Y., 2011. Trends of extreme precipitation and associated synoptic patterns over the southern Iberian Peninsula. Journal of Hydrology. 409, 497-511.
Hosseini, M., 2009. Recognition of synoptic condition associated precipitation on Khazar region. M.A Thesis in climatology, Isfahan University.
Hosseos, E. C., Lolis, J., & Bartzokas, A., 2008. Atmospheric circulation patterns associated with extreme precipitation amounts in Greece. Adv. Geosice, 17, 5-11.
Janbaz Ghobadi, G.R., Mofidi, A.,& Zarrin, A., 2011. Determining the synoptic pattern of winter heavy precipitations on the southern coast of the Caspian sea, Geography and Environmental Planning, 42, 23-40.
Keables, M. J., 1989. A synoptic climatology of bimodal precipitation distribution in the upper Midwest. J. Climate, 2, 1289-1294.
Khoshhal dastjerdi, J., 1997. Analyze and provide synoptic climatology model for more than 100 mm precipitations on the southern coast of the Caspian sea. Ph.D Thesis in climatology, Tarbiat Modares University.
Lana, A., Campins, J., Genov’es, A., & Jans, A., 2007. Atmospheric patterns heavy rain events in the Balearic Islands. Advances in Geosciences, 12, 27-32.
Lashkari, H., 1996. Synoptic patterns of heavy precipitations on the southwestern of the Iran, Ph.D thesis in climatology, Tarbiat Modares University.
Lorenzo, S. J., Lopez, A., Codobilla, M. J., Garcia, M. A., & Raso, J. M., 2008. Torrential rainfall in northeast of the Ibrian Peninsula: synoptic patterns and WeMO influence. Adv. Sci. Res, 2, 99-105.
Masoodian, S.A., 2011. Climate of Iran, Mashhad: Tos Sharie Press.
Mastrangelo, D., Horvath, K., Riccio, A., & Miglietta, M. M.(2011. Mechanisms for convection development in a long-lasting heavy precipitation event over southeastern Italy. Atmospheric Research, 100, 586-602.
Mofidi, A., Zarrin, A., & Janbaz Ghobadi, G.R.(2008. Determining the synoptic pattern of winter heavy precipitations and comparison with autumn heavy precipitations on the southern coast of the Caspian Sea, The 1st. International conference on the Caspian region environmental changes, 24-25 August 2008, University of Mazandaran, Babolsar.
Mofidi, A.,& Zarrin, A., 2005. The synoptic study of low pressure systems of the Sudan in heavy rainfall in Iran. Geographical Research, 77, 113-136.
Mohamadi, B., & Masoodian, S.A., 2010. Synoptic analysis of the Iran heavy precipitations. Development and Geography Journal, 19, 47-70.
Najar saliqe, M., 2001. The synoptic patterns of summertime rainfall in the southeastern Iran. Geographical Research, 62, 114-125.
Rezai Banafsheh, M., Najafi, M.S, Naghizadeh, H., & Abkharabat. S.(2015. The study of relationship between variability of extreme precipitation and the main factors affecting the precipitation in the west and northwest of Iran. Geography and environmental hazards, 4, 133-153.