The Role of Sistan 120 Days Wind in Thermal Advection of East and Southeast Iran

Document Type : Full length article


1 PhD Student in Climatology, Tabriz University, Tabriz, Iran

2 Assistant Professor of Climatology, University of Tehran, Tehran, Iran

3 Assistant Professor of Climatology, Razi University, Iran

4 MA in climatology, Jahad Daneshgahi, Kermanshah, Iran


The 120-day winds of Sistan are considered as the most important and well-known climatic factors in eastern regions of Iran during hot period. They have various effects on the region. For example, these winds make dust storm, more evapotranspiration and sand prairie in this region. Generally, as these winds have great impacts on the environment and human life, they should be studied from different climatic aspects. Given the importance of the winds, this study aimed at evaluating the role of these winds in declining the temperature of the region. The results will prove one of the positive environmental aspects of these winds during hot period of year in eastern dessert regions of Iran. However most effects of these winds were negative and considered as one of the life limiting factors in the east Iran.
Materials and methods
The period used in this study is the 2480 days in 22 years (2012-1993) from May until end of September. The atmospheric circulation types have been extracted using daily mean of the 850 hPa geopotential height data. Then, the agglomerative hierarchical cluster analysis with the ward algorithm and Euclidean distance has been used to identify atmospheric circulation types over Iran in the mentioned period of years. Finally, 5 atmospheric circulation types have been identified in this period of years. We, then, have analyzed wind speed and direction, the wind thermal advection in levels of 1000, 925, 850 and 700 hPa, and also the thermal advection of atmospheric vertical profiles.
Results and discussion
The Position of Maximal Cores of Temperature (Thermal Equator)
As a matter of fact, maximal cores of temperature imply the position of earth thermal equator. Pattern 1, in which 120- day winds of Sistan cover east and southeast parts of Iran more intensely and more widely, reveals that maximal temperature covers Iraq and west part of Iran, while in the same latitude there is cool weather in east part of Iran. Pattern 2 in which the 120-days winds of Sistan have less intensity and expansion shows that thermal equator belt of east is penetrating into northern latitudes, even though lower temperature is still recorded in east and southeast Iran. This is compared with west parts of Iran and Iraq. Generally, these 2 synoptic patterns reveal that 120-day winds of Sistan with northern direction lead to a decrease in the temperature of east and southeast Iran. Besides it makes thermal equator belt move to southern latitudes. There are the patterns 3, 4, and 5. In these patterns, 120-day Sistan winds are not dominant in the area. This leads to an increase in the temperature of the area and a core formation of maximal temperature in east and southeast Iran. Unlike patterns 1 and 2, in these patterns eastern regions of Iran have higher temperature than Mesopotamia and west Iran. As a result, the advection of eastern winds in the region makes thermal equator penetrate northern altitudes as it covers east and southeast Iran. Due to this phenomenon, eastern regions record much higher temperature than the regions in Mesopotamia and west Iran, although they are in the same latitude.  
Wind advection in eastern and southeastern regions of Iran during hot period of year is considered as one of the most important and most effective climatic phenomena having great impacts on environment and communities. There are two advection orders during this period of year, the advection of northern winds (120- day winds of Sistan) and the advection of eastern winds. Eastern winds mostly cover eastern and northeastern regions of Iran, while northern winds mostly cover eastern and southeastern regions. The calculation of thermal advection during the existence of each wind demonstrates that during the advection of northern winds, a core of negative thermal advection is made in east and southeast Iran. As these winds are intensified, the intensity of this negative thermal core is also increased. This phenomenon reveals that this is the heat transmission from the dominant regions of this negative thermal advection to surrounding regions which provide cool weather in east and southeast areas of the country. Besides, vertical profile of atmosphere also proves the altitudinal expansion of this core of negative thermal advection through higher levels. A core of negative thermal advection is made during the advection of eastern winds, although this core dominates less regions limiting to eastern regions of Iran. Besides, a core of positive thermal advection is made in southeast part of Iran. This phenomenon not only leads to heat aggregation, but also makes a core of maximal temperature in the region and transfers thermal equator to east and southeast of Iran. Moreover, temperature in eastern half of Iran is lower than that of the west and also that of Mesopotamia during the advection of 120- day winds, while this region shows higher temperature than west of Iran and Mesopotamia  in the absence of 120- day winds. Therefore, the advection of northern winds (120- day winds of Sistan) makes thermal equator of the earth move to southern latitudes in southeast Iran to decrease the temperature of the region.


Main Subjects

جانسون، ر.آ. و ویچرن، د.د. (1386). تحلیل آماری چند متغیری کاربردی، برگردان حسینعلی نیرومند، مشهد: انتشارات آستان قدس رضوی.
حسین‏زاده، س. ر. (1376). بادهای 120 روزة سیستان، فصل‏نامة تحقیقات جغرافیایی، 47: 103ـ127.
خسروی، م. (1387). تأثیرات محیطی اندرکنش نوسان‏های رودخانة هیرمند با بادهای 120 روزة سیستان، فصل‏نامة تحقیقات جغرافیایی، 91: 19ـ49.
خسروی، م. (1389). بررسی توزیع عمودی گرد و غبار ناشی از طوفان‏ در خاورمیانه با استفاده از مدل NAAPS مورد: سیستان ایران، چهارمین کنگرة بین‏المللی جغرافی‏دانان جهان اسلام، زاهدان، ص 1ـ22.
خسروی، م. و نظری‏پور، ح. (1391). مطالعة همدید تیپ‏های هوای غالب منطقة سیستان (مطالعة موردی: ایستگاه زابل)، پژوهش‏های جغرافیای طبیعی، 44(3): 39-62.
دوستان، ر. (1392). شناسایی کانون‏های فشار مؤثر در وقوع باد 120 روزة سیستان و بلوچستان، نخستین کنفرانس ملی آب و هواشناسی ایران، کرمان، ص1ـ8.
طاووسی، ت.؛ نجارسلیقه، م. و صفرزایی، ن.ا. (1391). بررسی پارامترهای برداری باد و نقش آن در طوفان‏های گرد و غباری سیستان ایران، جغرافیا و پایداری محیط، 2: 19ـ30.
علیجانی، ب. و رئیس‏پور، ک. (1390). تحلیل آماری همدیدی طوفان‏های گرد و خاک در جنوب ‏شرق ایران (مطالعة موردی: منطقة سیستان)، فصل‏نامة مطالعات جغرافیایی مناطق خشک، 5: 107ـ129.
قویدل ‏رحیمی، ی. (1389). نگاشت و تفسیر سینوپتیک اقلیم با استفاده از نرم‏افزار Grads، تهران: انتشارات سها دانش.
گندم‏کار، ا. (1389). تعیین گسترة افقی باد سیستان با استفاده از تحلیل خوشه‏ای، فصل‏نامة جغرافیای طبیعی، ص 67ـ76.
گندم‏کار، ا. و کیارسی، ف. (1385). تولید برق بادی و پمپاژ آب کشاورزی با استفاده از انرژی باد در نواحی بادخیز استان اصفهان، کنفرانس جغرافیا و قرن 21، نجف‏آباد، ص 1ـ15
مفیدی، ع. و کمالی، س. (1391). بررسی و تحلیل ساختار طوفان‏های گرد و غباری در دشت سیستان با استفاده از مدل اقلیمی مقیاس منطقه‏ای RegCM4 (مطالعة موردی: 30 جولای 2001)، اولین همایش ملی بیابان، کرج، ص 1ـ16.
مفیدی، ع.؛ حمیدیان‏پور، م.؛ نجارسلیقه، م. و علیجانی، ب. (1392). تعیین زمان آغاز، خاتمه، و طول مدت وزش باد سیستان با بهره‏گیری از روش‏های تخمین نقطة تغییر، جغرافیا و مخاطرات محیطی، 8: 87ـ112.
نجارسلیقه، م. (1389). آثار مشترک تقابل حرارتی سیستم‏های جوی در کشورهای اسلامی (مطالعة موردی: بادهای 120 روزة سیستان)، چهارمین کنگرة بین‏المللی جغرافی‏دانان جهان اسلام، زاهدان، ص1ـ17.
یارنال، ر. (1385). اقلیم‏شناسی همدید و کاربرد آن در مطالعات محیطی، برگردان سید ابوالفضل مسعودیان، اصفهان: انتشارات دانشگاه اصفهان.
Alijani, B. and Raeispour, K. (2011). Statistical analysis synoptic dust storms in southeastern Iran (Case study: Sistan), Journal of Geographical Studies of Arid Zones, 5: 107-129.
 Alizadeh-Choobari, O.; Zawar-Reza, P. and Sturman, A. (2014). The “wind of 120 days” and dust storm activity over the Sistan Basin, Atmospheric Research, 143: 328-341.
Bollasina, M. and Nigam, S. (2011). The summertime ‘‘heat’’ low over Pakistan/northwestern India: evolution and origin, Clim Dyn, 37: 957-970.
Dostan, R. (2013). Identify effective pressure centers in the 120-day wind of Sistan and Baluchestan, Published the first national conference Meteorological Iran, Kerman, pp. 1-8.
Esteban, P.; Jones, F.D.; Martin-Vide, J. and Mases, M. (2005). Atmospheric circulation patterns related to heavy snowfall days in Andora, Pyrenees, International Journal of Climatology, 25: 319-329.
Gandomkar, A. (2010). Wind determining the horizontal extent of Sistan using cluster analysis, Journal of Physical Geography, PP. 67-76.
Gandomkar, A. and Kiarasi, F. (2006). Wind power generation and pumping of water using wind energy in windy areas of the province, Printing in 21st Century conference, geography and Najafabad, PP. 1-15.
Ghavidel Rahimi, Y. (2010). Mapping and interpretation software synoptic climate Grads, printing, Tehran: Soha Danesh.
Goudie, A.S. and Middleton, N.J. (2001). Dust storm in South West Asia, Acta Univ Car., XXXV, SUPPLEMENTUM, pp. 73-83.
Hoseinzadeh, S.F.(1997). 120-day winds of Sistan, Journal of Geographical Research, 47: 103-127.
Johnson, R.A. and Vichren, D.D. (2007). Applied multivariate statistical analysis, Translated by: H. A. Niromand, print, Mashhad: Astan Quds Razavi.
Khosravi, M. (2008). 120-day winds of Sistan environmental impact interaction with the fluctuations of the Helmand River, Journal of Geographical Research, 91: 19-49.
Khosravi, M. (2010). Vertical distribution of dust storms in the Middle East with the NAAPS model: Iranian Sistan, Published in the Fourth International Congress of Islamic World Geographers (2010), Zahedan, PP. 1-22.
Khosravi. M. and Nazaripour, H. (2012). Synoptic study of prevailing Sistan region Types (case study: Zabol station), The study of physical geography, 44(3): 39-62.
Miri, A.; Ahmdi, H.; Ekhtesasi, M.R.; Panjehkeh, N. and Ghanbarie, A. (2009). Environmental and socio-economic impacts of dust storms in Sistan Region, Iran. Journal of Environmental Studies, 66: 343-355.
Mofidi, A. and Kamali, S. (2012). Review and analysis of dust storms in the plains of Sistan using the regional scale climate model RegCM4 (study published: 30 July 2001), First National Conference desert, Karaj, PP. 1-16.
Mofidi, A.; Hamidianpour, M.; Najarsaligheh, M. and Alijani, B. (2013). Determine the start, end and duration of wind Sistan methods to estimate the change point, Geography and environmental hazards, 8: 87-112.
Najarsaligheh, M. (2010). Joint effects of thermal contrasting weather systems in Islamic countries Case study: Sistan winds of 120 days, Published in the Fourth International Congress of Islamic World Geographers, Zahedan, PP. 1-17.
Ramaswamy, C. (1962). Breaks in the Indian summer monsoon as a phenomenon of interaction between the easterly and the subtropical westerly jet streams, Tellus, 14A: 337-349.
Rashki, A.; Kaskaoutis, D.G.; Rautenbach, C.J.W; Eriksson, P.G.; Qiangl M. and Gupta, P. (2012). Dust storms and their horizontal dust loading in the Sistan region, Iran, Aeolian Research, 5: 51-62.
Spengler, T. and Smith, R.K. (2008). The dynamics of heat lows over flat terrain, Q. J. R. Meteorol. Soc, 134: 2157-2172.
Spengler, T.; Reeder, M.J. and Smith, R.K. (2005). The dynamics of heat lows in simple background flows, Q. J. R. Meteorol. Soc, 131: 3147-3165.
Tavosi, T.; Najarsaligheh, M. and Safarzaei, N.A. (2012). Wind direction and parameters of its role in Iran's Sistan dust storms, Geography and environmental sustainability, 2: 19-30.
Yarnal, R. (2006). Synoptic climatology and its application in environmental studies, Translated by S. A. Masoodian, print. Isfahan, Isfahan University Press.
Volume 49, Issue 3
October 2017
Pages 477-489
  • Receive Date: 25 June 2016
  • Revise Date: 14 January 2017
  • Accept Date: 07 February 2017
  • First Publish Date: 23 September 2017