Document Type : Research Article
Authors
1 Professor Agro meteorology, Department of Water Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad
2 Ferdowsi University of Mashhad
Abstract
Abstract
Drastic Precipitations in unmorally times always are one of the important factors that created abundant damages in different geographical areas. In this research, three Precipitations that occurred in summer 2009 in Mashhad were investigated. The investigation of variation graphs of meteorological parameters show significant decreasing of air pressure and temperature and increasing of relative humidity and dew point in days of occurrence precipitation compare with previous days. The result of physical analysis by using thephigram showed that existent of thick cloud whit noticeable perceptible water in sky of local in days of occurrence precipitation. Also situation of LCL and FCL levels and difference of height between top of cloud whit FCL and amount of dynamical indexes of CAPE, SHOW and KINX explains noticeable potential energy of ascendable air mass and suitable conditions for drastic instability of weather. For example amounts of dynamical indexes for torrent day (15 Sep) obtained 953.4, -4.67 and 35.30 respectively that are demonstrator of hard instability in this day. The investigation of surface isobars map showed contrast of tow Low and High pressure systems in east of country. Also 850 hpa isobars map indicate advection of warm weather from south to northeast that is similar whit surface pressure patterns. Therefore prove that developing of Siberian High pressure in warm season synchronic whit advection of warm and humid weather from south that caused drastic instability suddenly and this subject is supported physical analysis of vertical profile of atmosphere.
Keywords: Vertical profile, Summer rainfall, Advection of warm weather, Pressure systems, Physical and Dynamical indexes of atmosphere
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