Changes in Effective Components of Peak Rainfalls in Iran

Document Type : Full length article


1 PhD in Synoptic Climatology, Faculty of Geographical Sciences, Kharazmi University, Tehran, Iran

2 Associate Professor of Climatology, Faculty of Geographical Sciences, Kharazmi University, Tehran, Iran

3 MSc in Urban Climatology, Faculty of Geographical Sciences, Kharazmi University, Tehran, Iran


Since the spatial and temporal distribution of rainfall in Iran is influenced by distribution of global circulation systems, the slightest change in its pattern can lead to severe weather abnormalities. Therefore, spatial and temporal abnormalities of rainfall and extreme changes in rainfall intensity and differences in precipitation types are one of the main characteristics of Iranian rainfall. Climate change is one of the problems of human society and is a threat to the planet Earth. The increase in the temperature of the earth has caused profound and extensive changes in the Earth's climate, causing changes in the time and place of precipitation, which has caused a lot of damage, especially in the last decade. The purpose of this study was to identify and study the changes in the heavy rainfall components of Iran in relation to changes in the middle tropospheric systems. 
Materials and methods
In this study, we received daily rainfall data of 53 synoptic stations from Iran Meteorological Organization from 1984 to 2013. The cluster analysis and zoning were conducted using Euclidean distance method and Ward's method. For zoning based on cluster analysis, we also used seven variables of consecutive rainy days. The final result was the division of the country into 3 regions according to the number of days. In the following, data from the upper atmosphere levels were used to investigate changes in the mechanisms of rainfall forming. The data are including discovery data of geopotential heights, u wind, v wind, omega, in 500 hpa level, and specific humidity at level 700 in daily average, and 1 * 1 degrees from the European Center for Medium Term Forecast (ECMWF). The statistical period of study was divided into two periods of 15 years (first study period 1984-1998 and second study period 1999-2013), the peak days for each area were determined in each of the two time periods. For each time period, the peak rainfall was 5 days. Then, the synoptic parameters were analyzed and compared in each study period. 
Results and discussion
In the second study period, the range of trough decreased and the depth of trough increased. The central core of geo-potential heights in the first time period is greater than the second period of study. In other words, the core in the first period is 5400 geo-potential meters, which in the second interval it decreased to 5350 geo-potential meters. In area 2, in the second period of study, the high elevation in the convergence region of the Arabian Sea is more shallow and in a more inappropriate position than the first pattern. The area 3, in the second study period, is located in northwest Iran behind the trough, and cold weather is falling with low amount of rainfall. In 3 areas, in the second period of study, the amount of moisture has decreased and caused the rainfall of the second interval to decrease relative to the first interval.  
In the second period of study (1999-2013), the range of trough has decreased and the depth of trough has increased. The Omega component showed that in the second study period, the mean omega-negative peak of the area was reduced. The Omega component study showed that in the second study period, the mean omega-negative in the target area was reduced. It was also found that the direction of the wind streams in the second period was reduced due to the flow. The amount of moisture in the second period of study has also decreased and has caused the second period rainfall to decrease over the first period. In the study of the synoptic components of second area, it was found that in the second period of studies (1999-2013), located on the convergence area of the Arabian Sea, is more shallow and in a more inappropriate position than the first pattern. This caused the maximum moisture content to fall to 5 grams per kilogram. Investigation of the synoptic components of the third region, revealed that in the second study period, the study area, especially the northeast Iran, is somewhat ahead of the trough, and the average annual precipitation in this is increasing in the second period. It can also be understood that the northwest Iran is located behind the trough with a fall in the cold weather. The rainfall in this part has decreased during the period.


Main Subjects

احمدی، م. (1394). واکاوی بارش فوق‏سنگین 23 اسفند 1392 مولد سیلاب مخرب در شهرستان بندرعباس، مجلة دانش مخاطرات، 2(3): 307-324.
بابایی فینی، ا. و فرج‏زاده، م. (1381). الگوهای تغییرات مکانی و زمانی بارش در ایران، برنامه‌ریزی و آمایش فضا، 6(4): 51-76.
بابایی فینی، ا. و فرج‏زاده، م. (1382). نمایه‏های مکانی بارش و تغییرات آن در ایران، سومین کنفرانس منطقه‏ای و اولین کنفرانس ملی تغییر اقلیم، اصفهان.
خوش‏اخلاق، ف.؛ نبوی، س.ا. و عباسی، ا. (1391). تحلیل سامانه‏های همدید بارش‏های شدید دورة سرد سال در استان‏های خراسان رضوی و شمالی، نشریة جغرافیا و برنامه‏ریزی (دانشگاه تبریز)، 16(40): 97-118.
علیزاده، ا. (1385). اصول هیدرولوژی کاربردی، چ 7، مشهد: دانشگاه امام رضا.
کرم‏پور، م.؛ زارعی چقابلکی، ز.؛ میرهاشمی، ا. و رستمی فتح‏آبادی، م. (1395). تحلیل همدید- ترمودینامیک مخاطرة سیلاب‏های لحظه‏ای ناشی از بارش‏های رگباری مناطق کوهستانی (حوضة قره‏سو)، مجلة دانش مخاطرات، 3(1): 75-90.
گندم‏کار، ا. (1389). بررسی همدید بارش‏های شدید در نواحی جنوبی استان بوشهر، مجلة چشم‏انداز جغرافیایی، 4(10): 143-157.
گندم‏کار، ا. و خادم‏الحسینی، ا. (1388). بررسی روند تغییرات بارش در زابل، مجلة آمایش محیط، 6: 65-77.
مسعودیان، ا. و عطایی، ﻫ. (1383). شناسایی فصول بارشی ایران به روش تحلیل خوشه‏ای، مجلة علوم انسانی دانشگاه اصفهان، 18: 1-12.
مفاخری، ا. (1396). تأثیر تغییرات سیستم‏های میان تروپوسفری بر تمرکزگرایی بارش ایران، رسالة دکتری اقلیم‏شناسی، گروه جغرافیا، دانشگاه خوارزمی تهران.
منتظری، م. (1388) تحلیل زمانی‏- مکانی بارش‏های فرین روزانه در ایران، مجلة جغرافیا و برنامه‏ریزی محیطی، 20(34): 125-140.
یارنال، ب.(1993). اقلیم شناسی همدید و کاربرد آن در مطالعات محیطی، ترجمه ابوالفضل مسعودیان،1385،اصفهان: انتشارات دانشگاه اصفهان.
Ahmadi, M. (2016). Extra heavy rainfall study 13 March 2016 The destructive flooding factor in Bandar Abbas, Knowledge of hazards, 2(3): 307-324.
Alijani, B.; O’Brien, J. and Yarnal, B. (2008). Spatial analysis of precipitation intensity and   concentration in Iran, Theoretical and Applied Climatology, 94: 107-124.
Alizadeh, A. (2006). Principales of applied hydrology, Seventh Edition, University of Imam Reza, Mashhad. 912p.
Babaei Feini, O. and Farajzadeh, M. (2002). Patterns of spatial and temporal variations in rainfall in Iran, Journal of Spatial Planning,6(4): 51-76.
Babaei Feini, O. and Farajzadeh, M. (2003). Spatial Indexs of precipitation and its changes in Iran, Third Regional Conference and First National Conference on Climate Change, Isfahan.
Carla Lima, K.; Satyamurty, P. and Reyes Fernández, 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.
Croitoru, A-E.; Piticar, A. and Burada, D. (2015). Changes in precipitation extremes in Romania, Quaternary International, PP. 1-11.
Dayan, U.; Margalit, Z.B. and Sharon, M.E. (2001). A Severe Autumn Storm Over the Middle, East: Synoptic and Mesoscale Convection Analysis, Theoretical and Applied Climatology, 69: 103-122.
Deluis, M.; Gonzaales-hidalgo, J.; Longares, L.A. and Stepank, P. (2009). Seasonal Orecipitation Trends in the Mediterranean Iberian Peninsula in Second half of 20th Ventury, International Journal of Climatology, 29: 1312-1323.
Elagib, N.A. (2010). Exploratory analysis of rain days in central Sudan, Meteorology and Atmospheric Physics, 109: 47-59.
Gandomkar, A. and Khadem al-Husseini, A. (2009). Study the trend of rainfall changes in Zabol, Journal of Environmental, 6: 56-77.
Gandomkar, A. (2010). Sinoptic study of severe rainfall in the southern regions of Bushehr province, Journal of Geographic Perspectives, 4(10): 143-157.
Karampour, M.; Zarei Chaghabalki, Z.; Mir Hashemi, A. and Rostami Fath Abadi, M. (2016). Synoptic analysis - Thermodynamics of the instantaneous flood hazards caused by rainfall in mountainous regions (Ghareh Souh basin), Journal of hazard knowledge, 3(1): 75-90.
Khosh Akhlagh, F.; Nabavi, S.A. and Abbasi, A. (2012). Analysis Synoptic Systems of Severe Precipitation Cold period of year in Razavi and Northern Khorasan Provinces, Journal of Geography and Planning (Tabriz University), 16(40): 97-118.
Limsakul, A. and Singhruck, P. (2016). Long-term trends and variability of total and extreme precipitation in Thailand, Atmospheric Research, 169: 301-317.
Manea, A.; Birsan M.; Tudorache G.; Cărbunaru, F. and Changes, A. (2016), Changes in the type of precipitation and associated cloud types in Eastern Romania (1961–2008), Atmospheric Research, 169: 357-365.
Mafakheri, O. (2017). Effect of mid-troposphere systems variation over Iran's precipitation concentration, Thesis for Ph.D degree climatology, Supervisor: Dr Mohammad Saligheh, Department of Geography, Kharazmi University of Tehran.
Masoodian, A. and Ataie, H. (2005). Identify the rainy seasons of the cluster analysis, Journal of Research university Eesfahan, 18: 1-12.
Montazeri, M. (2009). Analysis of temporal-spatial rainfall of hazardous daily in Iran, Journal of Geography and Environmental Planning, 20(34):125-140.
YarnaL, B. (2006). Synoptic climatology and its application in environmental studies, Translation by Abolfazl Masoudian, Isfahan University Publishers, Isfahan.
Volume 51, Issue 1
April 2019
Pages 87-103
  • Receive Date: 08 March 2018
  • Revise Date: 27 November 2018
  • Accept Date: 27 November 2018
  • First Publish Date: 21 March 2019