The influence of lower tropospheric circulation of Arabian high pressure on Iran precipitation

Document Type : Full length article


1 Assistant Professor, Faculty of Geography, University of Tehran, Iran

2 M.A. Student of Synoptic Climatology, Faculty of Geography, University of Tehran, Iran


Atmospheric circulation patterns result in different weather conditions. Rainfall changes are controlled by seasonal and irregular variations of atmospheric circulation pattern. A variety of climate changes such as drought and flood can result in changes in the spatio-temporal precipitation, one of the important parameters of heterogeneity in moisture transmission and injection in the rainy systems of Iran. One component of the atmospheric circulation of moisture transmission is the high pressure centers and the most important point is their location on the water surface.
Saudi Arabian high pressure is one of the main elements of the general circulation on the lower level of the atmosphere which affects climatic characteristics of the region. Therefore, the main aim of recent study was to investigate Saudi Arabian High Pressure circulation patterns and its impacts on the moisture and precipitation by using cluster analysis.
Materials and Methods
In order to assess the role of Saudi Arabian high pressure patterns on the rainfall and moisture of Iran, we have derived hourly data viz., 00, 06, 12 and 18 global standard geopotential data in height of 850 hPa for 11 years during the period 2000 to 2010 for the area in 30° to 80° longitude and 5° to 30° latitude with a spatial resolution of 1° * 1°. The data are from the re-analysis of the ERA interim center of Europe medium-term forecasts (ECMWF).
By scripting in MATLAB software, we employed cluster analysis for correlation method and performed Clustering based on the threshold correlation coefficient of 0.5. We initially obtained the 160 groups from which the greater number of days whose the higher correlation were more than 0.5 have been placed in one group.
In the later steps to reduce the groups between correlations to less than coefficient threshold, we have reduced number of groups in each step using reiteration of operation by calculation and integration of the average of any of days of the each cluster groups to finally obtain the 5 large patterns.
In order to evaluate the resulting patterns all the days in each pattern were pulled out. Traced maps, the mean geopotential height, zonal and meridional component of wind were obtained through the scripting GrADS software. In addition, rain and moisture advection based on the total days of each pattern on a large scale were mapped and frequency of the monthly patterns were calculated as well.
Results and Discussion
In this study, 5 large patterns were detected such that 2 of them were rare patterns and 5 dominant patterns. The 4 patterns have been more abundant in the cold season and 1 pattern in the warm season. The second pattern of the cold season is the highest and most pervasive precipitation of Iran, and fourth pattern are in second order. The summer pattern has lowest rainfall pattern during the 11 years of the study.
The transfer and placement of center core of high pressure over the seas in the south of the country, especially over the Arabian Sea, are involved in southwest flows. It is clear that the moisture injection could be observed in the second and fourth pattern of high precipitation and high pressure core with the stretching on the sea. Moreover, the existence of a trough at 500 mb level over the country has additional impact on the recent condition.
The first and second patterns have less rainfall with the high pressure displacement to the western and northern parts. In the warm season of the year, the expansion of the Ganges low pressure at the lower level and integration and expansion of the subtropical high pressure and Saudi Arabian high pressure at the higher levels over the country result in sharply decrease in the amount of moisture and precipitation in the country. This causes consequently a reduction in the activity of this high pressure. While there are other atmospheric systems in the higher latitudes such as the blocking system and its link with Saudi Arabia high pressure behavior, this can lead to specific situations that caused different precipitation conditions in various parts.
The results showed that the spatio-temporal behavior of Saudi Arabian high pressure such as east-west, north-south displacement and even center core stretching has very significant role in the infusion of moisture and consequently the precipitation over Iran. The spatial distribution of precipitation in the country depends on the location, shape and area of circulation of high pressure. Generally, the high pressure has more impact at cold season with remarkable role in moisture and precipitation of Iran. However, in the warm seasons, the role of the high pressure is greatly reduced due to its integration with subtropical high pressure and transfer to the North over the country and increase in air stability of the region.


Main Subjects

جهان‏بخشی، م. (1388). تحلیل سینوپتیکی ارتباط پرفشار جنب حاره‏ای عربستان با بارش‏های جنوب و جنوب غرب ایران، پایان نامه کارشناسی ارشد، دانشکده علوم زمین، دانشگاه شهید بهشتی.
حلبیان، ا. (1390). شناسایی تنوع آرایش جوی در وردسپهر میانی و اندرکنش الگوهای همدید مؤثر بر ایران، نشریة تحقیقات کاربردی علوم جغرافیایی، 12(21): 131 ـ 156.
خوش‌اخلاق، ف عزیزی، ق. و رحیمی، م. (1391). الگوهای همدید خشک‌سالی و ترسالی زمستانه در جنوب غرب ایران، نشریة تحقیقات کاربردی علوم جغرافیایی، 12(25): 57 ـ 77.
علیجانی، ب. (1388). اقلیم‌شناسی سینوپتیک، چ 3، تهران: سمت.
علیجانی، ب.؛ محمدی، ح. و بیگدلی، آ. (1386). نقش الگوهای فشار در بارش‏های سواحل جنوبی دریای خزر، فصلنامة جغرافیایی سرزمین، 4(16): 37 ـ 51.
علیجانی، ب. (1366). رابطة پراکندگی مکانی مسیرهای سیکلونی خاورمیانه با سیستم‏های هوایی سطح بالا، فصلنامة تحقیقات جغرافیایی، 4: 125 ـ143.
علیجانی، ب.؛ عزیزی، ق. و رضایی، پ. (1383). بررسی اثر الگوهای سینوپتیک در تغییرات زمانی سیلاب‏های جنوب دریای خزر (مطالعة موردی رودخانه‏های شفا رود و تالار)، فصلنامة جغرافیایی سرزمین، 1(1): 4 ـ 19.
فتاحی، ا. و رحیم‌زاده، ف. (1388). ارتباط انسو با الگوهای گردش جوی زمستانة ایران، فصلنامة جغرافیا و توسعه، 7(15): 21 ـ 44.
فتاحی، ا. و رضیئی، ط. (1388). الگوهای گردش جوی روزانه بر روی ایران، فصلنامة تحقیقات جغرافیایی، 24(93): 45 ـ 74.
فرج‌زاده، م.؛ کریمی احمدآباد، م.؛ قائمی، ه. و مباشری، م. (1386). چگونگی انتقال رطوبت در بارش زمستانة غرب ایران (مطالعة موردی بارش 3-7 ژانویة 1996)، فصلنامة مدرس علوم انسانی، 13(1): 193 ـ 217.
قشقایی، ق. (1375). بررسی اثر فرابار سیبری بر بارش‏های پاییزی سواحل جنوبی خزر، پایان‏نامة کارشناسی ارشد، استاد راهنما بهلول علیجانی، گرایش اقلیم و برنامه‌ریزی محیطی، دانشگاه تربیت معلم.
کریمی احمدآباد، م. (1386). تحلیل منابع تامین رطوبت بارش‏های ایران، رساله دکتری جغرافیای طبیعی، گرایش اقلیم شناسی، دانشکده علوم انسانی، دانشگاه تربیت مدرس.
کریمی احمدآباد، م. و فرج‌زاده، م. (1390). شار رطوبت و الگوهای فضایی- زمانی منابع تامین رطوبت بارشهای ایران ، نشریة تحقیقات کاربردی علوم جغرافیایی، 19(22): 109 ـ 127.
لشگری، ح. (1375). الگوی همدیدی بارش‏های شدید جنوب غرب ایران، رسالة دکتری، استاد راهنما هوشنگ قائمی، گروه جغرافیا، دانشگاه تربیت مدرس.
لشگری، ح. و محمدی، ز. (1394). اثر موقعیت استقرار پُرفشار جنب حاره‏ای عربستان بر سامانه‏های بارشی در جنوب و جنوب غرب ایران، فصلنامة پژوهش‏های جغرافیای طبیعی، 47(1): 73 ـ 90.
مفیدی، ع. و زرین، آ. (1384). بررسی سینوپتیکی تأثیر سامانه‏های کم‌فشار سودانی در وقوع بارش‏های سیل‌زا در ایران، فصلنامة تحقیقات جغرافیایی، 77: 113 ـ 136.
مفیدی، ع. و جعفری، س. (1390). بررسی نقش گردش منطقه‏ای جو بر روی خاورمیانه در وقوع طوفان‏های گرد و غباری تابستانه در جنوب غرب ایران، مطالعات جغرافیایی مناطق خشک، 2(5): 17 ـ 45.
یارنال، ب. (1390). اقلیم‌شناسی همدید و کاربرد آن در مطالعات محیطی، ترجمة ا. مسعودیان، چ 2، اصفهان: انتشارات دانشگاه اصفهان.
Alijani, B. (2009). Synoptic Climatology, Vol.  3, Tehran: Samt.
Alijani, B.; Mohammadi, H. and Bigdeli, A. (2007). The Role of Pressure Patterns on the Precipitation of the South Coast of Caspian Sea, Sarzamin Geography Quarterly, 16: 37-51.
Alijani, B.; Azizi, Gh. and Rezaei, P. (2004). The Effect of Synoptic Patterns on the Floods of the Southern Caspian Sea Coast, Case Study: Shafarood and Talar Rivers, Sarzamin Geography Quarterly, 4(1): 4-19.
Alijani, B. (1988). The Relationship Between Spatial Distribution Middle East Cyclone Routes With High-Level Aerial Systems, Geographical Research Quarterly, 4: 125-143.
Domroes, M.; Kaviani, M. and Schaefer, D. (1998). An Analysis of Regional and Intra-annual Precipitation Variability over Iran Using Multivariate Statistical Methods, Theoretical And Applied Climatology, 61: 151-159.
Farajzadeh, M.; Karimi Ahmadabad, M.; Ghaemi, H. and Mobasheri, M.R. (2007). Mechanism of Water Vapor Transport in Winter Rainfall Over the West of Iran (A Case Study: 1-7 January 1996), Journal of Humanities lecturer, 13(1): 193-217.
Fattahi, E. and Raziei, T. (2009). Daily Atmospheric Circulation Patterns over Iran, Geographical Research Quarterly, 93: 45-74.
Fattahi, E. and Rahimzadeh, F. (2009). The ENSO Relation With Wintery Atmospheric Circulation Patterns in Iran, Geography and Development Quarterly, 15: 21-44.
Jahanbakhshi, M. (2010). Synoptic Analysis The Relationship Between Saudi Arabia Subtropical High Pressure With Precipitations In The South and South West of Iran, Master's Thesis, Faculty of Earth Sciences, Shahid Beheshti University.
Halabian, A.H. (2011). Recognition of variety of the atmospheric configuration at mid- troposphere and the interaction between effective synoptic patterns over Iran, Applied Research of Geographic SciencesJournal, 11(21): 131-156.
Hayden, B.P. (1981). Cyclone Occurrence Mapping: Equal Area or Raw Frequencies, Monthly Weather Review, 109(1): 168-172.
Huth, R. (1996). An Inter comparison of Computer Assisted Circulation ClassificationMethods, International Journal of Climatology, 16: 893-922.
Karimi Ahmadabad, M. (2008). Analysis of  The Moisture Supplying Sources For Iran's Precipitation, Ph.D. Thesis The Natural Geography, Climatology Orientation, Faculty of Humanities, Tarbiat Modarres University.
Karimi Ahmedabad, M. And Farajzadeh, M. (2012). Moisture flux and spatial-temporal patterns of Moisture Supplying Sources For Iran's Precipitation, Applied Research of Geographic SciencesJournal, 19 (22): 109 127.
Khoshakhlagh, F.; Azizi, Gh. and Rahimi, M. (2012). The synoptic Patterns of wintertime drought and wet period in Southwestern of Iran, Geographical Sciences Applied Research Journal, 12(25): 57-77.
Klein., W.H. and Winston., J.S. (1958). Geographical Frequency of Troughs and Ridges In the Northern Hemisphere, 1949-1963, Monthly Whether Review, 93: 705-720.
Lamb, H.H. (1950). Types and Spells of Weather Around the Year In the British Isles : Annual Trends, Seasonal Structure of the Year, Singularities, Quarterly Journal of the Royal Meteorological Society, 76(330): 393-429.
Lamb, H.H. (1972). British Isles Weather Types and a Register of Daily Sequence of Circulation Patterns, 1861–1971, Geophysics Mem., Vol. 116.
Lashgari, H. and Mohammadi, Z. (2015). The Role of Saudi Arabian Sub-Tropical High Pressure on the Rainfall Systems on South and Southwest Iran, Journal of Physical Geography, 1: 71-90.
Lashgari, H. (1996). The Synoptic pattern of heavy precipitations south West of Iran, Thesis, The Department of Geography, Tarbiyat Madras University.
Lund, I.A. (1963). Map-Pattern Classification by Statistical Methods, Journal of Applied Meteorology, 2(1): 56-65.
Mofidi, A. and Jafari, S. (2011). The Role of Regional Atmospheric Circulation over The Middle East on The Occurrence of Summer Dust-storms in Southwest Iran, Arid Regions Geographic Studies, 2(5): 17-45.
Mofidi, A. and Zarrin, A. (2005). Synoptic Analysis of Influence of Sudan Systems in Occurring of Torrential Precipitations in Iran, Geographical Research Quarterly, 77: 113-136.
Pettersen, S. (1950). Some Aspects of the General Circulation of the Atmosphere, Centenary Proce., R.M.S., PP. 120-155.
Qashqai, GH. (1996). Investigate Effect of The Siberian High Pressure On The Fall Rainfals Southern Coast of The Caspian Sea, Master's Thesis, The Tendency of Climate And Environmental Planning, Tarbiyat Moalem University.
Stark, L.P. (1965). Positions of Monthly Mean Troughs and Ridges in the Northern Hemisphere, 1949-1963, Monthly Weather Review, 93: 705-720.
Vicente-Serrano, S.M. and Lopez-Moreno, J.I. (2006). The Influence of Atmospheric Circulation at Different Spatial Scales on Winter Drought Variability Through a Semi-Arid Climatic Gradient in Northeast Spain, International Journal of Climatology, 26: 1427-1453.
Xu, X.D.; Miao, Q.; Wang, J. and Zhang, X. (2003). The Water Vapor Transport Model At The Regional Boundary During The Meiyu Period, Advances in Atmospheric Science, 20(3): 333-342.
Yarnal, B. (1993). Synoptic Climatology In Environmental Analysis, A Primer, Belhaven Press, PP. 195.
Zarrin, A.; Ghaemi, H.; Azadi, M.; Mofidi, A. and Mirzaei, E. (2011). The Effect of Zagros Mountains on the Formation and Maintenance of Iran Anticyclone Using RegCM4, Meteorology and Atmospheric Physics, 112: 91- 100.
Zhang, R. (2001). Relations of Water Vapor Transport From Indian Monsoon With That Over East Asia And The Summer Rainfall In China, Advances in Atmospheric Science, 18(5): 1005-1017.