Document Type : Research Paper

Authors

• Mahdi Modiri ¹
• Mahdi Khazaei ²
• Mohammad Hasan Mahutchi ³

¹ Malek-e Ashtar University

² Shahid Beheshti University

³ University of Tehran

Abstract

In this study have been paid on analysing Thunderstoms in a period of 25 years in Shiraz (1984-2008). Therefore, data on sea level pressure, geopotential height levels 850 and 500 hpa in the rainfall day of NCEP/NCAR databse prepared and extraction levels above the map drawing software environment GRADS Were drawn. The extreme rainfall patterns Related to Shiraz have been identified and analyzed. By examining maps of sea level pressure, 850 and 500 hpa, three general patterns were identified for Shiraz thunderstorm rainfall. In the first pattern (1 March 1998), the low-pressure lingual of the Sudan country, large parts of the study area is located. The system In addition provides moisture, instability in the level do too. And in the level of 850 and 500 hpa, area studied the influence of anticyclonic centers are located in the western and ridges. In second type of the pattern (December 6,2003) at sea level, the area studied is affected by center anticyclone, and the level of 850 and 500hpa area at the front of the trpugh with a curved contour 1450 and 5720 geopotential meters located and the conditions are very unstable at this level. And the third pattern (26 March 2003) Low-pressure center with a central pressure of 1004hpa is located on the country. At this level, the currents are such that relatively moist air flows from the Caspian to the North West and the West. The levels of 850 and 500hpa area studied are located under the trough axis above and instability intensifies levels above.

Keywords

• Synoptic analysis
• thunderstorm rainfall
• the instability indexes
• Shiraz weather station

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