Document Type : scientific-research article
Authors
1 Meteorology of Atmospheric Science and Meteorological Research (ASMERC), Tehran, Iran
2 Meteorology, West Azarbaijan Applied Research Meteorology Center, Urmiah- Iran
Abstract
Objectives: The main goal of this study is to identify sources of formation and characteristics of pressure patterns, and meteorological quantities that affect heavy rainfalls in spring in the West Azerbaijan province.
Method: According to maps and meteorological data in different levels of atmosphere, weather patterns leading to heavy precipitations in spring were investigated in six years (2003-2008) in West Azerbaijan province. For this purpose, meteorological data, weather charts at standard pressure levels, total precipitation and gridded sea level pressure (SLP), 500-hPa geopotential height fields and their anomalies data were used. In addition, relative vorticity and its advection were computed at 500-hPa level for rainfall episodes.
Findings/Results: The results indicate that all types of events are controlled by the strong cut of low-pressure systems that are located in east of Mediterranean Sea and remain stagnant for 3-7 days in this area.
Conclusion: In all studied cases, , relative vorticity and its advection on mid-troposphere(500-hPa) level reveal a significant increase in the days before the heavy rainfall period with the maximum vorticity reaching 4×10-5s-1 to 6×10-5s-1 and maximum advection reaching 6×10-9s-2 to 12×10-9s-2). One day before the start of heavy rainfalls, vorticity and its advection reached their maximum values. As such, it can be used as a predictor of intense rainfall episodes in spring.
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