نقش جابه جایی مکانی پُرفشار عربستان و رودباد جنب‏ حاره‏ ای در الگوهای همدیدی و ترمودینامیکی ترسالی‏ های شدید جنوب و جنوب‏ غرب ایران

نوع مقاله : مقاله کامل

نویسندگان

1 دکترای اقلیم‏ شناسی سینوپتیک، گروه جغرافیای طبیعی، دانشکدة علوم زمین، دانشگاه شهید بهشتی تهران

2 دانشیار گروه جغرافیای طبیعی، دانشکدة علوم زمین، دانشگاه شهید بهشتی تهران

چکیده

اگرچه بارش در هر اقلیمی از اهمیت اساسی برخوردار است، در اقلیم‏های خشک نقشی حیاتی در زندگی انسان‏ها پیدا می‏کند. نوار جنوبی کشور ایران در هم‏جواری دو سامانة اقلیمی مهم قرار دارد که آرایش مکانی و ساختار دینامیکی آن‏ها الگو، شدت، و گسترة بارش‏ها را تعیین می‏کند. بررسی انجام‏شده بر روی نقشة ترازهای زیرین، میانی، و بالایی وردسپهر به ‏صورت چشمی و استفاده از تحلیل عاملی نشان داد که در همة ‏روزهای بارشی، در دو ترسالی شدید، منطقة پُرفشارِ عربستان جابه‏جایی شرق‏سویِ قابل ‏توجه داشته و در نمونه‏های فراگیر در شرق طول 55 درجة شرقی قرار داشته است. مهم‏ترین منبع رطوبتی در همة سامانه‏های بارشی در لایة وردسپهر زیرین دریاهای عرب و عمان هست؛ این رطوبت از طریق جریانات شرقی گردش واچرخندی پُرفشار عربستان به درون سامانة سودانی و سپس در امتداد زبانة کم‏فشار بر روی منطقه منتقل ‏شده است. درصورتی‏که در لایة میانی وردسپهر این رطوبت به‏صورت شاخه‏ای از جریانات شرقی منطقة TICZ به جلوی ناوة مدیترانه‏ای‏ـ که در این شرایط تا جنوب عرض 15 درجة شمالی گسترش داردـ فرارفت می‏شود. مناسب‏ترین موقعیت رودباد جنب‏حاره‏ای برای تشدید ناپایداری‏های لایة زیرین محدوده‏ای بین مصر تا غرب خلیج‏فارس است که هستة مرکزی رودباد در جنوب اردن استقرار می‏یابد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effects of Spatial Movement of Arabia Subtropical High Pressure and Subtropical Jet on Synoptic and Thermodynamic Patterns of Intense Wet Years in the South and South West Iran

نویسندگان [English]

  • Zainab Mohammadi 1
  • Hassan Lashkari 2
1 PhD Candidate in Climatology, Faculty of Earth Science, Shahid Beheshti University, Iran
2 Associate Professor of Climatology, Faculty of Earth Science, Shahid Beheshti University, Iran
چکیده [English]

Introduction
Although precipitation is of great importance in all climates, it plays a vital role in the arid and semi-arid regions. The spatial and temporal distribution of precipitation in all climates is affected by special synoptic structures in which one or two systems play the controlling role. The southern Iran is located adjacent to two important climate systems whose spatial arrangements determine the timing and amount of precipitation in the mentioned region. Therefore, it is important to study the possibility of predicting the drought and wet years in this geographical region of Iran according to its strategic role in the ecology, agriculture, industry, transportation, and politics. The study was conducted on Hormozgan, Boushehr, Kohkilouyeh-va-Boyerahmad, Chahar-mahal-va-Bakhtiari, and Khuzestan Provinces in Iran.
Materials and methods 
The daily precipitations in the selected stations were extracted, harmonized and arranged in a 30 year statistical period. Then, the situation of each station was determined from the viewpoint of drought and humidity using the SIPA criterion and DIP software. We have selected the years in which intense wet years were half of the selected stations, based on the mentioned criteria. These years have been selected as the samples of intense wet years. The atmospheric data of the mentioned years were extracted from the website http://www.esrl.noaa.gov, and the daily maps of these years were created at levels of 1000 and 500 hPa in the longitude of-40 degree west to 100 degree east and the latitude of zero (the equator) to 80 degree north using Grads software. The Arabian subtropical high pressure nuclei were determined for all days and their maps were created as the output maps using ArcGIS10.3 software. The data were reproduced in a matrix with the dimensions of 67×2145 based on the daily precipitation of more than 5 millimeters. The study area, located between the latitudes 0 to 80 degree north and -40 to 100 degrees east, has a number of days according to the spatial data resolution which was 2.5×2.5 geographical degree. Afterwards, justification of the data distribution according to the special values, variance percentage and accumulation variance was determined for analysis of the factors. Just 12 factors had the values larger than 1 in the primary analysis. The principle component analysis and Varimax rotation showed that concentrating on the correlation of 13 factors can explain 89.18 percent of the pattern’s behavior.
Finally, the dominant patterns in the selected intense wet year samples were extracted through studying the maps of 1000 and 500 hPa from the twelve extracted factors. Then, we have analyzed the maps of subtropical jet stream, divergent and convergent flux, special moisture, temperature blow, and etc. Moreover, the maps of different levels in all rainy days of the intense wet years were reviewed. Comparison of the repetitive patterns resulting from the review and the principle factor analysis provided similar results.  
Results and discussion 
Our study showed that in all the rainy days, the central nucleus of the Arabian anticyclone cell at all levels of 850 and 700 hPa was located in the east part of the longitude 45 degree E. When the anticyclone central nucleus is located in the east part of the longitude 55 degree E, the precipitations are more extensive, and cover all the regions from Khuzestan to Hormozgan. As it can be seen, in the rainy days, one or two divergent flux nuclei are located on Oman Sea or western Arab Sea and Gulf of Aden. In such condition, the streams in the lower levels of troposphere (from sea level to 850 hPa) are changed into eastern streams in northern Oman Sea and gradually on the Arab Sea. This condition is the most suitable mechanism for moisture advection towards the Sudan low pressure. In the same day, two strong nuclei of convergent moisture flux are dominated on Ethiopia and central Arabia which receive the moisture transmitted from the warm seas. The highest moisture advection towards the Sudan system is done under the layer of 850 hPa from Arab Sea, Oman Sea and the Gulf of Aden. Because of the topographic condition at levels higher than 850 hPa, this advection comes much lower, and the moisture transmitted from the transition branch may add to this moisture from the tropical convergence region. With the moisture advection in the lower levels, proper thermodynamic condition is provided for the development of convection clouds on the region. These clouds initially appear as mass clouds on Sudan and Red Sea, and then on Arabia, and then gradually move to Iran through the southern streams before trough at levels of 850 hPa and higher. Then, the clouds grow and extend through involving in the upward streams dominated on the front trough and under the subtropical jet stream, which are located on Red Sea and northwest Arabia. The proper temperature blow and diabatic warming resulting from condensation process provide a severe condition in the northern part of the jet.
Conclusion
In order to have an intense wet year in the south and south west of Iran, the eastern movement of Arabian high pressure is considered as an important factor. With the eastern movement of this high pressure, a proper synoptic condition for advection of moisture toward the precipitation system is provided. A proper condition is also provided for the extension of the Mediterranean trough towards the southern latitudes on the south east part of African desert and cold advection on the region at the middle and upper layers of troposphere. The Arabian high pressure has very high ability for wet condition, especially at the lower layers, because of its dynamic structure. Therefore, the moisture moved through the divergent flux toward the southern systems is considerable and provides significant potential energy for the convection systems. The cold advection from the northern latitudes and the warm advection from the subtropical latitudes provide proper heat gradient for intensification of the subtropical streams in the northwest domain of the Arabian high pressure. These jet streams are formed in the limits of northeast Arabia and provide proper dynamic condition for intensification of intense convection streams in the Northern Arabia and Southern Iran. The convection clouds cause intense precipitations on the region because of the access it has to the moisture of the southern warm seas and also the moisture moved from the northern branch of the tropical convergence region.

کلیدواژه‌ها [English]

  • Arabian high pressure
  • synoptic pattern
  • Sudan Low
  • wet year
  • south and south west Iran
احمدی گیوی، ف.؛ ایران‏نژاد، پ. و محمدنژاد، ع. (1389). اثر پُرفشارهای جنب‏حاره و سیبری بر خشک‏سالی‏های غرب ایران، چهاردهمین کنفرانس ژئوفیزیک ایران، تهران، ۲۱ـ۲۳: 5-9.
حجازی‏زاده، ز. (1372). بررسی سینوپتیکی پُرفشار جنب‏حاره‏ای در تغییر فصل ایران، پایان‏نامة دکترا، دانشگاه تربیت مدرس.
خوش‏اخلاق، ف.؛ عزیزی، ق. و رحیمی، م. (1391). الگوهای همدید خشک‏سالی و ترسالی زمستانه در جنوب‏غرب ایران، نشریة تحقیقاتکاربردیعلومجغرافیایی، 12(25): 57ـ77.
سلیقه، م. و صادقی‏نیا، م. (1389). بررسی تغییرات مکانی پُرفشار جنب‏حاره در بارش‏های تابستانة نیمة جنوبی ایران، فصل‏نامة جغرافیا و توسعه، 17: 83ـ98.
قائمی، ه.؛ زرین، آ.؛ آزادی، م. و فرج‏زاده اصل، م. (1388). تحلیل الگوی پُرفشار جنب‏حاره بر روی آسیا و افریقا، فصل‏نامة مدرس علوم انسانی، 1: 219 ـ245.
قویدل رحیمی. ی. (1389). نگاشت و تفسیر سینوپتیک اقلیم با استفاده از نرم‏افزارGrads ، سها دانش.
کریمی احمدآباد، م. (1386). تحلیل منابع رطوبتی بارش‏های ایران، دانشکدة علوم انسانی، دانشگاه تربیت مدرس تهران.
کریمی احمدآباد، م. و فرج‏زاده، م. (1390). شار رطوبت و الگوهای فضایی- زمانی منابع تأمین رطوبت بارش‏های ایران، نشریة تحقیقات کاربردی علوم جغرافیایی، 22: 109ـ127.
لشکری، ح. (1375). الگوی سینوپتیکی بارش‏های شدید جنوب‏غربی ایران، پایان‏نامة دکتری، دانشگاه تربیت مدرس.
لشکری، ح. و محمدی، ز. (1394). اثر موقعیت استقرار پُرفشار جنب‏حاره‏ای عربستان بر سامانه‏های بارشی در جنوب و جنوب‏غرب ایران، پژوهش‏های جغرافیای طبیعی، 1: 73ـ90.
لشکری، ح.؛ متکان، ع.ا.؛ آزادی، م. و محمدی، ز. (1396). تحلیل همدیدی نقش پُرفشار جنب‏حاره‏ای عربستان و رودباد جنب‏حاره‏ای در خشک‏سالی‏های شدید جنوب و جنوب‏غرب ایران، پژوهش‏های دانش زمین، 8(30): 141ـ163.
محمدی، ز. (1396). تحلیل همدیدی نقش موقعیت مکانی پُرفشار جنب‏حاره‏ای و رودباد جنب‏حاره‏ای در خشک‏سالی‏ها، ترسالی‏ها، شروع و پایان و طول دورة بارشی جنوب و جنوب‏غرب ایران، رسالة دکتری، دانشگاه شهید بهشتی.
منصورفر، ک. (1388). روش‏هایپیشرفتةآماریهمراهبابرنامه‏هایکامپیوتری، تهران: مؤسسة انتشارات دانشگاه تهران.
نجارسلیقه، م. (1385). مکانیزم‏های بارش در جنوب‏شرق کشور، مجلة پژوهش‏هایجغرافیایی، 55: 1-13.
Ahmadi-Givi, F.; Iran-Nejad, P. and Mohammad-Nejad, A. (2010). Impact of subtropical high pressure and droughts, West Siberia, Iran, fourtten of the Geophysics Conference of Iran, Tehran, 21-23: 5-9.
Bell, G.D. and Bosart, L.F. (1989). A 15-year climatology of northern hemisphere 500 mb closed  cyclone and anticyclone centers, Monthly Weather Review, 117, 2142-2163.
Barry, R.G., R.J. Chorley. (1976) Atmosphere, Weather, and Climate, Volume 208 of University Paperbacks, 460pp.
He, C. & Zhou, T. Clim Dyn (2014) The two interannual variability modes of the Western North Pacific Subtropical High simulated by 28 CMIP5–AMIP models, Clim Dyn, 43: 2455-2469DOI 10.1007/s00382-014-2068-x.
Davis, R.E.; Hayden, B.P.; Gay, D.A.; Phillips, W.L. and Jones, G.V. (1997). The North Atlantic Subtropical Anticyclone, Journal of Climate, 10: 244-278.
Farajzadeh Asl, M.; Ghaemi, H.; Zarrin, A. and Azadi, M. (2009). The Analysis of Spatial Pattern of Subtropical Anticyclones over Asia and Africa, MJSP, 13(1) :219-245 .( In Persian)
Galarneau, T.J.L.F. Bosart, and A.R. Aiyyer,(2006) Closed Anticyclones of the Subtropics and Midlatitudes: A 54-Yr Climatology (1950–2003) and Three Case Studies. Meteorological Monographs, 55, 349–392, https://doi.org/10.1175/0065-9401-33.55.349.Gao, Y. (1981). Some aspects of recent research on the Qinghai-Xizang (Tibetan) Plateau Meteorology, Bulletin of the American Meteorological Society, 62(1).
Ghaemi, E.; Zarrin, A.; Azadi, M. and Farajzadeh Asl, M. (2009). Analyzing the patterns of subtropical high pressure over Asia and Africa, Journal of Humanities, 1: 219-245.
Ghavidel Rahimi, Y. (2010). The synoptic mapping and interpreting the climate using Grads software, SahaDanesh.
Hastenrath F. (1990). Climate dynamic of the tropics, Climate and circulation of Th Tropics.
Heim Jr, R. R. (2002). A review of twentieth-century drought indices used in the United States. Bulletin of the American Meteorological Society, 83(8), 1149-1165Hejazizadeh, Z. (1996). Evaluation of a subtropical high-pressure synoptic weather in Iran, Ph.D thesis, Tehran: Tarbiat Modares University.
Karimi, M. and Farajzade, M. (2012). Flow of Moisture and Spatial Patterns - Time of Iran's Rainfall Moisture Supply Resources, Journal of Applied Geosciences Research, 11(22): 109-128.
Krishnamurti, T.N. (1971). Tropical east-west circulations during the northern summe, Journal of Atmospheric Science, Vol. 28.
Krishnamurti, T.N.; Daggupaty, S.M.; Fein, J.; Kanamitsu, M. and Lee, J.D. (1973). Tibetan High and upper tropospheric tropical circulations during northern summer, Bulletin of the American Meteorological Society, 54(12): 234-249.
Lamb, H.H. (1972). Climate, Present, Past and Future: Fundamentals and climate now, Vol. I.
Lashkari, H.; Matkan, A.A.; Azadi, M. and Mohammadi, Z. (2017). Synoptic analysis of the role of Saudi Arabia subtropical high pressure subtropical and polar jet streams and severe droughts in South and South West of Iran, Journal of Researches in Earth Sciences, 8(2): 141-163. (In Persian)
Lashkari, H. (1996). The synoptic pattern of intense precipitations in the south west of Iran. PhD Thesis, Faculty of Human Sciences, Tarbiat Modarres University, Tehran, Iran. (In Persian)
Lashkari, H. and Mohammadi, Z. (2015). The effect of the location of the Arabian subtropical high pressure on the precipitation systems in the south and southwest of Iran, Researches of Natural Geography, 47(1): 73-90.
Lashkari, H.; Matkan, A.A.; Azadi, M. and Mohammadi, Z. (2017). Synoptic analysis of the role of Saudi Arabia subtropical high pressure subtropical and polar jet streams and severe droughts in South and South West of Iran, Journal of Researches in Earth Sciences, 8(2): 141-163.
MansourFar, K. (2009). The advanced statistical methods and computer programs, Tehran University press.
Martius, O.; Sodemann, H.; Joos, H.; Pfahl, S.; Winschall, A.; Croci-Maspoli, M.; Graf, M.; Madonna, E.; Mueller, B.; Schemm, S.; Sedláček, J.; Sprenger, M. and Wernli, H. (2013). The role of upper-level dynamics and surface processes for the Pakistan flood of July 2010, Q.J.R. Meteorol. Soc., 139: 1797-1780. doi:10.1002/qj.2082.
Mason R.B. and Anderson, C.E. (1963). The development and decay of the 100 mb summertime anticyclone over southern Asia, Monthly Weather Review, 93.
Mohammadi, Z. (2017). The synoptic analysis of the role of the spatial location of subtropical high pressure and subtropical jet on wet years, drought, start, end and duration of precipitation in the south and southwest of Iran, PhD Thesis, dr Hassan lashkari Shahid Beheshti University, Tehran, Iran. (In Persian)
Najarsliga, M. (2006). Rainfall Mechanisms in the South East of Iran, Geographical Research, 38(55): 1-3.
Neyama, Y. (1968). The morphology of the subtropical anticyclone, Journal of Meteorological Society of Japan, Vol. 46.
Parker, S.S.; Hawes, J.T.; Colucci, S.J. and Hayden, B.P. (1989). Limatology of 500 mb Cyclones and Anticyclones, 1950-85, Monthly Weather Review, 117pp.
Qian, Y.; Zhang, Q. Yao, Y. and Zhang, X. ( 2002). Seasonal variation and heat Preference of the south asia high, Advances in Atmospheric Sciences, Vol. 19.
Reed, T.R. (1939). Thermal aspect of the high-level anticyclone, Monthly WeatheReview, 67(7).
Saligheh, M. and Sadeghinia, M. (2008). Spatial variation of summer precipitation in the southern half of the subtropical high pressure Iran, Journal of Geography and Development, 17: 83-98.
Thompson, R.D. (1998). Atmospheric processes and systems, Routledge, 194 pp USA, 478 pp.
Tomozeiu, R.; Stefan, S. and Busuioc, A. (2005). Winter Precipitation Variability and Larg-scale Circulation Patterns in Romania, Journal of Theoritical and Applied Climatology, 81: 193-201.
Zhang, Q. and Wu, G. (2002). The bimodality of 100hPa south asia high and its relationship to the climate anomaly over east asia in summer, Journal of the Meteorological Society of Japan, 80(4).