Monitoring of Two Radar Echoes for a Tornado in Mountain
Using the radar data of CINRAD/SA in Qinhuangdao and CINRAD/CC in Chengde, NCEP reanalysis data, mesoscale physical diagnosis and disaster report, a tornado in Pingquan county of Chengde on 20 July 2009 is analyzed, the preliminary conclusions indicate that the tornado take place in valley which is higher terrain in the west and lower terrain in the east, cold air move southtoward, the momentum of upper-level NW jet stream go down, which make the component V of low-level wind field in mesoscale system to increase along the western valley,＇ product an asymmetric secondary circulation of small-scale valley breeze, enhance cyclonic vortices and occur much more mesocyclone in outbreak zone of tornado. At Bei jing station, the vertical wind shear is 19.44 m · s -1 at the heights of 0-6 km, the index K is 24, SI is 4 ℃ at 08：00, K is 28 ℃, SI is 0 ℃ at 14：00. Because the rainfall quickly is evaporated under the action of strong radiation in the afternoon, so it supply the short-time vapor conditions for keeping tornado. C wave rang radar displays that there are five mesocyclones and two general storm cells in the east of valley from 13：06 to 14：36, and three times onTVSdata are at 13：30, 14：06, 14：36, respectively. The maximum vorticity in the lower level is 29 m · s- 1, height is 0.8 km, the moving direction of storm is from NNW to SSE, horizontal moving speed is 60-70 km · h -1 , maximum echo intensity is 69 dBZ, tornado strength limit within F0-F1. Comparing with the special profile of the Doppler radial velocity and mesocyclone, it is found the duration time until tornado touching the ground below 1 km is 10 min and the duration time of rotation above 4 km height is 45 min.
Mountainous tornadoMesocycloneTVS indexTime-limit of early warning
NETL
NSTL
万方数据
维普
