Comparative Analysis on Occurrence and Maintenance Mechanism of Two Short-Term Rainstorms in Hunan Province under Control of Subtropical High
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Abstract:
Based on the ground automatic station data, doppler weather radar data, satellite hourly TBB data and NCEP reanalysis data, we analyze the occurrence and maintenance mechanism of two short-term rainstorms in Hunan under the control of subtropical high in 2018. The results show that: (1) Under the condition of abundant water vapour and sufficient unstable energy and uplift, the short-term rainstorm weather can also be triggered in the anticyclone circulation in the strong subtropical high ridge. Its large-scale circulation characteristics are quite different from the typical rainstorm process in Hunan. (2) Before the occurrence of convective precipitation, the unstable energy was significantly enhanced. The humidification in the middle and lower layers was obvious, providing energy and water vapour conditions for the rainstorm. (3) The two processes were respectively affected by the disturbance of the outer cloud system of the tropical cyclone on the south side of the subtropical high and the intrusion of weak cold air. There was weak disturbance or weak shear forming at 925 hPa, cooperating with the ground mesoscale convergence line. Near-surface dynamic uplift triggered convective precipitation. Affected by solar radiation during the day, it could freely touch heat convection. Topographic uplift was also an important trigger mechanism. Thermal convection occurred on the windward slope, accounting for 84%. (4) The radar echoes of two short-term rainstorms were obvious precipitation echoes with a low centroid and high efficiency. The environmental wind and its vertical wind shear were small, which was not conducive to the organized development of convective storms. However, the thunderstorm monomer moved slowly, which was conducive to long-term heavy precipitation in the same area.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.