بررسی سینوپتیکی بارش‌های سنگین در جنوب ایران( مطالعه موردی بارش 31 دسامبر 1984 لغایت 4 ژانویه 1985 حوضه آبریز رودخانه دالکی)

  Synoptic analysis of heavy rain in South of Iran (case study : Heavy rain in the Dalaki river basin in period of 31 December 1984 - 4 January 1985)    A. Parandeh Khozani. ( * ),  Senior Expert of Climatology in Esfahan Meteorology Bureau   email: parandeh_153@yahoo.com     H. Lashkari.   Associate professor of climatology, Sahid Beheshti University, Tehran, Iran.   Received: 18 May 2009 / Accepted: 10 March 2009, 35-37 P     Extended Abstract   1- Introduction   Heavy rain is the most common and widespread of all weather-related natural disasters that have caused considerable losses to the human throughout history.   In south of Iran and Dalaki river basin this damages are significant.   Thus, Diagnosis and Prediction of distractive heavy rains and its intensity in region is very important (essential).   The aim of this study is to recognize the synoptic pattern leading to distractive rain in Dalaki river basin located in south of Iran.     In order to prevent damages of these phenomena and water resource management, it is better to study heavy rain in different regions with synoptical method.     2- Metodology   In order to obtain this, Circulation pattern of the upper and lower and its advection during precipitation was investigated. At First, Daily synoptic maps from surface to 500 hpa levels of 48 hours before the occurrence of precipitation were investigated and finally considering their arrange, extension, direction of movement, the position of cyclones and anti-cyclones were analyzed. Furthermore, in upper levels trough lines were carefully traced and analyzed.       3- Discussion   Strengthing activity mentioned system has been influenced by following factors:   -The existence of an anticyclone on Oman Sea and the East of Arabestan provides enough moisture for feeding this system in the highest precipitation day.   -The Spread of Siberian anticyclone tongue over Iran and South of Iran, before the start of precipitation, causes the falling of cold weather from high latitude and increase the thermal gradian over the region.   -The existence of high Azores center at the levels of 500 and 700 Hectopascal that causes strengthening thermal gradian over the region by falling of cold weather from its East over the North of Africa and Meditranian Sea and also made Sudan heat low centers and Red Sea convergence zone to be active and become dinamic and termodinamic   -The existence of high Arabestan at the levels of 700 and 500 Hectopascal is need for transition of hot and humid weather into the system.     4- Conclusion   Synoptic analysis of heavy rain in Dalaki river basin Located in south of Iran , showed that in surface level ,heavy rain mainly is caused by Siberian anticyclone and high Azores and simultaneous merging of the Sudan heat low (SHL) system and Mediterranean frontal system (MFS). In upper levels of Atmosphere high Azores located in back of system and high Arabestan in front of system and deep Trough North Africa are the main factors that could intensify the heavy rain intensities over the basin.   Keywords: Synoptic analysis Heavy rain Dalaki river basin South of Iran     References   JAMAB Engineering Consulting (water) Company, with Ministry of Energy, Water Comprehensive Plan, Surface Water Resources, Shapour-Dalaki (Helleh) river basin, Volum1, Tehran, Iranian Ministry of Energy.   Arabi, Zahra. (1385). Synoptic Analysis of Precipitation in Period (21- 26) JUL (Tir) 1387 in Iran, Journal of Geographical Research, Number 56. Tehran.   Alijani, Bohlol. (1372). Precipitation Ascent Mechanisms in Iran, Journal Faculty of Literature and Humanities, Theacher Training University Tehran, Number 1, Tehran.   Lashkari, Hassan. (1375). 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