ISSN 1006-9895

CN 11-1768/O4

Characteristics of Strong Convective Wind Events Caused by Three Types of Convective Systems in Hubei Province
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Affiliation:

1.State key Laboratory of Server Weather, Chinese Academy of Meteorological Science, Beijing 100081;2.Institute of heavy rain, China Meteorological Administration, Wuhan 430205

Fund Project:

Special Scientific Research Fund of Meteorological Public Welfare Grant GYHY201506006Special Scientific Research Fund of Meteorological Public Welfare (Grant GYHY201506006)

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    Abstract:

    Using regional automatic weather station (AWS) data, together with radar and sounding over Hubei Province from 2012-2017, in this study, the authors classified the mesoscale convective systems (MCSs) that result in surface convective gales in Hubei (maximum wind speed ≥ 17 m/s) into three types (linear MCSs, nonlinear MCSs, and isolated convective storms). The temporal and spatial distributions of convective gales, the movement and propagation of corresponding convective systems, and their convective environments were investigated. The mechanism of the convective inflow gale and the roles of convection system organization and development are discussed, with particular reference to one case. The results indicate that: (1) A large number of nonlinear MCSs may be formed by isolated convective storms occurring in mountains or hills, which then move toward the plains. The peak time of the surface gales caused by isolated convective storms during the study period was around 1700 BJT (Beijing time), and the highest surface-gale frequency corresponding with nonlinear MCSs appeared around 1900 BJT. Gales caused by linear MCSs mainly occurred in plain areas. (2) Nonlinear MCSs and isolated convective storms were the primary systems triggering gales in Hubei, with 41.9% of the gales at the stations caused by nonlinear MCSs and 39.3% by isolated convective storms. (3) Although inflow gales on the surface account for only a small proportion, their corresponding convective systems were much larger and their durations much longer than the average of the same type. A case study of a long-life linear MCS (squall line) shows that the ground inflow gales were caused by the strong development of convection, and the moist warm inflow in front of the convective system enhanced the convective activity developing as feedback. Meanwhile, the inflow gales strengthened the vertical wind shear in the forward direction. This is why the strong ground inflow was more conducive to the organizational development of the convective system. (4) Although southwesterly winds constituted the mean steering flow in all three system types, linear MCSs mainly moved from west to east, nonlinear MCSs moved mostly from southwest to northeast, and isolated convective storms moved in more diverse directions with more backward-propagation phenomena. Relative to organized convective systems, isolated convective storms often occurred in more unstable or drier environments with weak vertical wind shear and lower wind speeds.

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History
  • Received:July 30,2018
  • Revised:
  • Adopted:
  • Online: June 04,2019
  • Published: