Identifying Dynamic and Thermodynamic Patterns of Winter Heavy Rainfall in Iran (1960-2010), a Case Study: 1974/12/05 Heavy Rainfall

Document Type : Full length article

Authors

1 PhD in Climatology of Lorestan University, Khorramabad, Iran

2 Assistant Professor, Department of Geography, Lorestan University, Khorramabad, Iran

3 Assistant Professor, Department of Meteorology, Atmospheric Science and Meteorological Research Center, Tehran, Iran

4 Professor, Meteorological Department, Meteorological Organization of Iran, Tehran, Iran

Abstract

Introduction
Changes and fluctuations in shape and type of precipitation have positive and negative effects and have an important role in different aspects of human life. The change in the pattern produces negative and positive secondary feedback to other climatic parameters followed by changes in hydrological cycles, water resources, natural and artificial ecosystems, human and animal habitats, security and economics. Therefore, the first parameter that can be considered is the study of drought. The presence of many parts of Iran in the dry and semi-arid belt of the world, on the one hand, and the determinant role that play at the water supply in the country on the other hand, thus it is important to be aware of the trend of rainfall changes in Iran. The nature of the heavy rainfall and the consequences of this have caused this phenomenon to be of particular importance in environmental planning and water resource management. The heavy rainfall affects the planning, design, operation and management of water resources. Therefore, it is necessary to know the characteristics of the behavior of such rainfall in order to predict and better manage water resources of the country. Heavy rainfall is one of the natural hazards that being aware of their occurrence can help reduce potential damage .The dynamic state index of the atmosphere, which expresses the degree of deviation from non-static, drought and viscosity of the atmosphere, can be used as a new theory to determine the location and time of high-pressure and low-pressure systems and their intensity.
Iran has arid and semi-arid climate, with its annual rainfall averaging about one-third of the world's annual values. Parts of Iran's rainfall are also more widespread in south-east part of the country, with high rainfall intensities. Therefore, the analysis of the synoptic and dynamic conditions of atmospheric circulation patterns is very important in identifying the factors affecting the occurrence of heavy rainfall, in particular, when these types of rainfall can cause floods and catastrophic consequences by converting runoff. Thus, with respect to the importance of the subject, the present study aimed to identify the dynamic and thermodynamic patterns that govern the day of the event of heavy winter precipitation.  
Materials and methods
In order to study the dynamic and thermodynamic patterns of the studied day, the vorticity of dynamical quantities include relative vorticity, absolute vorticity, Rossby-Ertel vorticity at pressure level, convergence and divergence, vertical speed at high system and dynamical quantities of potential temperature written and definedTo analyze the temporal variations of the above quantities, their graphs were analyzed in the selected range of 0 to 80 degrees longitude and latitude 10 to 60 degrees north for the 0000 and 1200 Greenwich hours. It should be noted that the maps of the day before and after the day were also examined at different levels to further understand the patterns governing the day of heavy rainfall, but to reduce the amount of content, only the maps of the day of heavy rainfall occurred at 0000 and 1200 Greenwich are provided.
Results and discussion
Examination of the thermodynamic and dynamical quantities during heavy rainfall events of the case series of winter 1960-2010 shows that on the day of the heavy rainfall event, December 5, 1974, the intensities of these quantities at 1200 Greenwich hour were greater than other times. Therefore, it can be said that the peak of heavy rainfall at this day is 1200 hours where the dynamical and thermodynamic quantities changes are as follows:
-      Increasing the potential temperature vertical gradient across the country; this increases the velocity of the subtropical jet as well as the potential vorticity values in the upper atmosphere.
-      The formation of a strong convergence zone at the country level and its adaptation to the mid-level divergence zones of the atmosphere that has led to the dynamic rise of the air in most areas. The high volume of upward atmospheric movements at this time has occurred in the western half, especially in the windward slopes of the Zagros Mountains.
-      Increase in relative vorticity and absolute vorticity of 500 hp levels corresponding to southwest - northeast flows of eastern part of the trough.
-      Increasing the potential vorticity values of Rossby-Ertel pressure levels of 500 and 50 hp and the co-entropy level of 330 Kelvin in the western part of the country due to factors such as potential temperature gradient increase, caused absolute vorticity increase, as well as increased static stability in the upper atmosphere.
Conclusion
Changes and fluctuations in shape and type of precipitation have positive and negative effects and they play an important role in different aspects of human life. The change in them produces negative and positive secondary feedback in other climatic parameters in hydrological cycles, water resources, natural and artificial ecosystems, human and animal habitats, security and economics. Heavy rainfall is one of the natural hazards that being aware of their occurrence can help reduce potential damage. Therefore, the analysis of the synoptic and dynamic conditions of atmospheric circulation patterns is very important in identifying the factors affecting the occurrence of heavy rainfall, in particular, when these types of rainfall can cause floods and catastrophic consequences by converting runoff. Thus, with respect to the importance of the subject, the present study aimed to identify the dynamic and thermodynamic patterns prevailing on the day of the event of heavy winter precipitation. The results show that during the event of heavy rainfall, a strong convergence zone was formed at the country level, which caused the dynamic ascension of the atmosphere in accordance with the atmospheric divergence zone. Under such conditions, the relative vorticity values increases corresponding to the eastern part of the trough, which also results in an increase in absolute vorticity values. In addition, at this time, the potential temperature vertical gradient is also increasing throughout the country. The Rossby-Ertel potential vorticity values of 500 and 50 hp and 330 Kelvin co-entropy levels can also be increased due to potential temperature gradient increase, absolute vorticity, as well as increased static stability at upper atmospheric levels.

Keywords


امیدوار، ک.؛ تنی، ن.؛ ابراهیمی، ر. و قیاثی، ا. (1397). واکاوی همدیدی دینامیکی بارش ابر سنگین 4 آذر 1393 (مطالعة موردی: کهگیلویه و بویراحمد)، فصل‏نامة جغرافیای طبیعی، 41: ۱۹-36.
بلیانی، س. و سلیقه، م. (1395). تحلیل و استخراج الگوهای جوی منجر به بارش‏های سنگین روزانة منطقة شمالی خلیج‏فارس (مورد مطالعه: حوضه‏های آبریز حله و مند)، نشریة تحلیل فضایی مخاطرات محیطی، 2: ۷۹-98.
سلامتی ‏هرمزی،‏ و.؛ امیدوار، ک.؛ کاوسی، ر. و حمزه‏نژاد، م. (1396). شناسایی و تحلیل همدیدی- دینامیکی الگوهای جوی سیلاب آبان 1394 در استان‏های ایلام و لرستان، مجلة علمی‏- ترویجی نیوار، 96: ۹-۲۷.
علیجانی، ب. (1381). اقلیم‏شناسی سینوپتیک، چ ۴، تهران: انتشارات سمت.
علیجانی، ب.؛ هاشمی‏عنا، س.ک.؛ عباس‏نیا، م. و پورهاشمی، س. (1393). واکاوی شرایط دینامیکی، ترمودینامیکی، و همدیدی رخداد بارش‏های سیل‏آسای ناحیۀ بسیار کم‏بارش جنوب شرقی ایران، فصل‏نامة جغرافیا و پایداری محیط، 4: ۱۳-1۸.
قویدل ‏رحیمی، ی. (1390). نگاشت و تحلیل همگرایی جریان رطوبت جو طی بارش فوق سنگین ناشی از طوفان حاره‏ای فت در سواحل چابهار، مجلة برنامه‏ریزی و آمایش فضا، 72: 101-118.
محمدی، ح.؛ فتاحی، ا.؛ شمسی‏پور، ع. و اکبری، م. (1391). تحلیل دینامیکی سامانه‏های سودانی و رخداد بارش‏های سنگین در جنوب ‏غرب ایران، تحقیقات کاربردی علوم جغرافیایی، 24: ۸-۲۴.
محمدی، ب. و مسعودیان س.ا. (1389). تحلیل همدید بارش­های سنگین ایران مطالعه موردی: آبان ماه 1373، فصلنامه جغرافیا و توسعه، 8 (19): 47-70.
مسعودیان، س.ا. (1390)، آب و هوای ایران، انتشارات شریعه توس مشهد، چاپ اول: 129.
مسعودیان، س.‏ا. و کارساز، س. (1393). تحلیل همدید الگوهای ضخامت بارش‏های سنگین ناحیة زاگرس جنوبی، نشریة جغرافیا و توسعه، 37: ۱۵-۲۷.
مصطفایی، ح.؛ علیجانی، ب. و سلیقه، م. (1394). تحلیل سینوپتیکی بارش‏های شدید و فراگیر در ایران، نشریة تحلیل فضایی مخاطرات محیطی، 4: ۶۵-76.
نوری، ح. (1391). بررسی شاخص جدید وضعیت دینامیکی جو در بارش های سنگین سواحل جنوبی خزر، جغرافیا و مخاطرات محیطی، ۲: ۱۳۳-147.
Agel, L.; Barlow, M.; Colby, F.; Binder, H.; Catto, J.; Hoell, A. and Cohen, J. (2018). Dynamical analysis of extreme precipitation in the US northeast based on large-scale meteorological patterns, Journal of Climate DynamicsSpringer-Verlag GmbH Germany, part of Springer Nature,1.
Ahasan M.N.; Rayhun, K.M.Z.; Mannan, M.A. and Debsarma, S.K. (2013). Synoptic Analysis of a Heavy Rainfall Event over Southeast Region of Bangladesh Using WRF Model, Journal of Scientific Research, 5(3): 421-434.
Alijani, B. (2003). Synoptic Climatology, Fourth Edition, Samt Publications, Tehran.
Alijani, B.; Hashemi, K.; Abbasnia, M. and Pourhashemi, S. (2014). Analysis of Dynamic, Thermodynamic, and Synoptic conditions of heavy rainfall Events in the South-East of Iran, Journal of Geography and Sustainability of Environment, 4(4): 13-28.
Balyani, S. and Saligheh, M. (2016). The Analysis and Extraction of Daily Heavy Rainfall Lead Atmospheric Patterns in Northern Portion of Persian Gulf (Helle and Mond Subbasin), Journal of Spatial Analysi Environmental Hazard, 3(2): 79-98.
Ghavidel Rahimi Y. (2011). Drawing and Analysis of Atomospheric Moisture Flux Convergence (MFC) During the Heavy Rainfall Caused by Phet Tropical Super Cyclione in Chabahr Coastal Region, Journal:  Spatial Planning, Vol.15, No 2(70): 101-118.
Jacobeit, J.; Rathmann, J.; Philipp, A. and Jones, P.D. (2009). Central European precipitation and temperature extremes in relation to large-scale atmospheric circulation types, Meteorol. Z., 18: 397-410.
Kato, T. and Aranami, K. (2005). Formation factors of 2004 Niigata-Fukushima and Fukui heavy rainfalls and problems in the predictions using a cloud-resolving model, Sola, 1:1-4.
Kenyon, J. and Hegerl, G.C. (2010). Influence of modes of climate variability on global precipitation extremes, J. Climate, 23: 6248-6262.
Masoodian S.A.   (2011). Climate of Iran, 1:129.
Masoodian S.A. and Karsaz S. (2014). Synoptic Analysis of Thickness Patterns at the Time of Heavy and Extensive Precipitations of South Zagros Area, Geography And Development Iranian Journal, 12(37): 15-28.
Masoodian, S.A. and Mohammadi, B. (2011). Analysis of Jet Stream Frequencies Associated with Super Heavy Rainfalls of Iran, Journal of Iran-water Resources Research,Volume 7, Issue 2, Pages 80-91.
Matlik, O. and Post, P. (2008). synoptic weather types that have caused heavy precipitation in Estonia in the period 1961-2005, Estonian journal of engineering, pp. 195-208.
Mohammadi, H.; Fatahi, A.; Shamsipour, A. and Akbari, M. (2012). Dynamic Analysis of Sudanese Systems and Heavy Rainfall Occurrence in Southwest Iran, Geographical Sciences Applied Research, 24: 24-8.
Mohammadi, B. and Massodiyan, S.A. (2010). Synoptic Analysis of Heavy Precipitation Events in Iran : case study of November 1994, Geoghraghy And Development Iranian Journal, 8(19): 47-70.
Mostafaii, H.; Alijani, B. and  Saligheh, M. (2016). Synoptic Analysis of Widespread Heavy Rains in Iran, Journal of Spatial Analysis Environmental Hazards, 2 (4) :65-76
Nouri, H. (2012). Investigation on a new dynamic state index in heavy precipitation events in the southern coasts of Caspian Sea, Journal of Geographey And Environmental Hazards, 2: 133-147.
Nouri, H. (2013). Investigation of the New Barometer Dynamic Status Indicator in Heavy Rainfalls in the Southern Caspian Sea, Geography and Environmental Hazards, 1(2): 117-147.
Oh, H.; Ha, K.-J. and Timmermann, A. (2018). Disentangling impacts of dynamic and thermodynamic components on late summer rainfall anomalies in East Asia, Journal of Geophysical Research: Atmospheres, 123: 8623-8633.
Oliveira, P.T.; Lima, K.C.; Santos, E. and Silva, C.M. (2013). Synoptic environment associated with heavy rainfall events on the coastland of Northeast Brazil Advances in Geosciences, Advances in Geosciences, 35: 73-78.
Omidvar, K.; Toni, N.; Ebrahimi, R. and Ghiati, A. (2018). Dynamic Synoptic Analysis of Heavy Cloud Precipitation 4 Dec 2014 Case Study of Kohgiluyeh and Boyer Ahmad, 11(41): 19-36.
Riosalido, R. (1990). Characterization of Mesoscale Convective Systems by Satellite Pictures during Previmet Mediterraneo-89, Segundo Simposio Nacional de Prediccion, Instituto Nacional de Meteorologia, Apartado 258(2807): 135-148.
 Harnack, R.; Jensan, D. T. and Cermak, J.R. (1998).  Investigation of Upper-Air Conditions Occurring With Heavy Summer Rain  in  UTAH, International of climatology, 18: 701 – 723.
Salamati Hormozi, V.; Omidvar, K.; Kavusi, K. and Hamzeh‏nejad, M. (2017). Recognition and Analysis Synoptic-dynamical Analysis of Flood Circulation Patterns in Ilam and Lorestan Provinces (Aban, 1394), Journal of Meteorlogical Orgabizatiom, 41: 96-97, Winter and Spring 2017, P. 9-27.
Scaife, A.A.; Folland, C.K.; Alexander, L.V.; Moberg, A. and Knight, J.R. (2008). European climate extremes and the North AtlanticOscillation, J. Climate., 21: 72-83.
Toreti, A.; Xoplaki, E.; Maraun, D.; Kuglitsch, F.G.; Wanner, H. and Luterbacher, J. (2010). Characterisation of extreme winter precipitation in Mediterranean coastal sites and associated anomalous atmospheric circulation patterns, Nat. Hazards Earth Syst. Sci., 10: 1037-1050.
Yiou, P. and Nogaj, M. (2004). Extreme climatic events and weather regimes over the North Atlantic: when and where?, Geophys.Res. Lett., 31: L07202.