科研之友
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摘要
The dynamic interaction of sea breeze with the prevailing synoptic flows can give rise to meteorological conditions conducive for the occurrence to the thunderstorms over coastal and adjoining regions. Here, we present a rare case study of the genesis of the thunderstorm that occurred on 4th May 2011 at 1500Z over Gadanki (13.5 degrees N, 79.2 degrees E), one of the tropical inland stations (100 km) near to the east coast of the Indian peninsula. The objective of present work is to understand the underlying physical mechanism of initiation of such convection over this region. A set of meteorological observations obtained from microwave radiometer profiler, eddy covariance flux tower system, and Doppler weather radar, are used for investigating the convection genesis characteristics. In conjunction with observations, to bridge the gap of lack of high resolutional spatial observations, the high-resolution (2 km) model analysis is developed using Weather Research and Forecasting (WRF) model and four-dimensional data assimilation technique. The analysis of thermodynamical and dynamical indices carried out from the model analysis as well as observations. Results obtained from this study indicated the presence of a wind discontinuity line and a warm air advection from the north Indian region towards Gadanki caused this area hot dry and convectively active. The sea breeze front propagated over hot and dry area few hours before the genesis of the thunderstorm. The moisture flux convergence increased with the inland propagation of sea breeze front. We found that the inland penetration of sea-breeze front caused advection of moist and cold air over warm and dry region; reduction in dew point depression causing bulging of dry line and lowering of lifting condensation level; development of shear in wind direction and speed; increase in low level convergence and vertical velocity, upward transport of moist air and finally increase in helicity of the environment. The wind shear instability and thermodynamic instability generated because of intrusion of sea breeze front at Gadanki region and reduction in dew point depression because of the incursion of moisture respectively. Convective instability developed due to the lifting of the dry and stable parcel under the influence of wind shear instability and its moistening due to advected moisture over this region are responsible for thunderstorm initiation over this region.
- 出版日期2016-10
