摘要
The effects of environmental vertical wind shear （VWS） on the intensity and rainfall asymmetries in Tropical Storm （TS） Bilis （2006） have been analyzed based on TRMM/TMI-estimated surface rainfall data, QuikSCAT wind fields, 850- and 200-hPa winds of the NCEP-NCAR reanalysis, precipitation data at 5-min intervals from automatic weather stations over China's Mainland, and the best track data of TS Bilis （2006）. The results show that the simultaneous and 6-hour-lagged correlation coefficients between VWS and storm intensity （the minimum central sea level pressure） are 0.59145 and 0.57438 （P 〈0.01）, respectively. The averaged VWS was found to be about 11 m s-1 and thus suppressed the intensification of Bilis （2006）. Distribution of precipitation in Bilis （2006） was highly asymmetric. The azimuthally-averaged rainfall rate in the partial eyewall, however, was smaller than that in a major outer rainband. As the storm intensified, the major rainband showed an unusual outward propagation. The VWS had a great impact on the asymmetric distribution of precipitation. Consistent with previous modeling studies, heavy rainfall generally occurred downshear to downshear-left of the VWS vector both near and outside the eyewall, showing a strong wavenumber-one asymmetry, which was amplified as the VWS increased.
The effects of environmental vertical wind shear （VWS） on the intensity and rainfall asymmetries in Tropical Storm （TS） Bilis （2006） have been analyzed based on TRMM/TMI-estimated surface rainfall data, QuikSCAT wind fields, 850- and 200-hPa winds of the NCEP-NCAR reanalysis, precipitation data at 5-min intervals from automatic weather stations over China's Mainland, and the best track data of TS Bilis （2006）. The results show that the simultaneous and 6-hour-lagged correlation coefficients between VWS and storm intensity （the minimum central sea level pressure） are 0.59145 and 0.57438 （P 〈0.01）, respectively. The averaged VWS was found to be about 11 m s-1 and thus suppressed the intensification of Bilis （2006）. Distribution of precipitation in Bilis （2006） was highly asymmetric. The azimuthally-averaged rainfall rate in the partial eyewall, however, was smaller than that in a major outer rainband. As the storm intensified, the major rainband showed an unusual outward propagation. The VWS had a great impact on the asymmetric distribution of precipitation. Consistent with previous modeling studies, heavy rainfall generally occurred downshear to downshear-left of the VWS vector both near and outside the eyewall, showing a strong wavenumber-one asymmetry, which was amplified as the VWS increased.
基金
supported by the National Natural Science Foundation of China under the Grant Nos.40828005
the National Natural Science Foundation of China under the Grant Nos.40921160382
the National Natural Science Foundation of China under the Grant Nos.40775060
the Key Project of the Ministry of Education of China,Grant No.02109
the State Key Basic Research Program 2009CB421500
the State Key Basic Research Program 2006BAC02B03
the State Key Basic Research Program GYHY200706033
supported by National Science Foundation of UAS Grants ATM-0427128
National Science Foundation of UAS Grants ATM-0754039
the ONR Grant 00014-06-10303
