ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 42 Issue 10 > 2016,42(10):1197-1212. DOI:10.7519/j.issn.1000-0526.2016.10.004 Prev Next
Characteristics’ Statistical Analysis of Gust Front Generated by Moving Thunderstorms in Shanghai
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Abstract:
Using conventional weather observations, dual Doppler radar data, Global Forecast System (resolution is 3 km) analysis field data, automatic weather station data, characteristics including synoptic background, sounding and radar features of 18 gust fronts generated by moving thunderstorms from 2009-2014 in Shanghai are analyzed. According to the mutual interaction between gust front and its original thunderstorm, these gust fronts are divided into two types. The first type tends to appear during the developing period of the original storm, moving in the same direction with the thunderstorm while keeping a certain distance, usually accompanied by the elevated rearinflow jet (RIJ) and its lifetime is longer than two hours. The other type usually occurs during the dissipating period of its original thunderstorm, moving far away from the thunderstorm in the same direction (12 cases) or different direction (4 cases). Statistical analysis shows that, as for the first type of gust front, it continuously lifts the warm and moist air in front of the storm while moving in the same direction with the storm. In addition, since the relative strong vertical wind shear and convective available potential energy (CAPE) play an important role in the maintenance of the height of the RIJ, the balance between the positive vorticity generated by RIJ and vertical wind shear and the negative vorticity generated by the cold pool is favorable for the development of the thunderstorm, so the thunderstorms develop and sometimes new storms initiate at the rear side of the gust front. As for the second type, because the gust front moves away from the original storm, and propagates as isolated waves, the cold and dry air at its rear side gradually weakens while affected by the environment. Gust front moving far away from the storm in the same direction cuts off the transport of the warm and wet air into the storm. Simultaneously, in the weaktomiddle vertical wind shear and weaktomiddle CAPE environment, the negative vorticity generated by the downward RIJ and cold pool is stronger than the positive vorticity generated by vertical wind shear, and the updraft leans back over the cold pool. These are unfavorable for the development of the storm. The lifetime of the storm is usually less than 2 hours.
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