Finescale spiral rainbands associated with Typhoon Rananim （2004） with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State...Finescale spiral rainbands associated with Typhoon Rananim （2004） with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State Mesoscale Model （MM5）. The finescale rainbands have two types： one intersecting the eyewall and causing damaging wind streaks, and the other distributed azimuthally along the inner edge of the eyewall with a relatively short lifetime. The formation of the high-velocity wind streaks results from the interaction of the azimuthal flow with the banded vertical vorticity structure triggered by tilting of the horizontal vorticity. The vertical advection of azimuthal momentum also leads to acceleration of tangential flow at a relatively high Mtitude. The evolution and structures of the bands are also examined in this study. Further investigation suggests that the boundary inflection points are related tightly to the development of the finescale rainbands, consistent with previous findings using simple symmetric models. In particular; the presence of the level of inflow reversal in the boundary layer is a crucial factor controlling the formation of these bands. The near-surface wavy peaks of vertical vorticity always follow the inflection points in radial flow. The mesoscale vortices and associated convective updrafts in the eyewall are considered to strengthen the activity of finescale bands, and the updrafts can trigger the formation of the bands as they reside in the environment with inflow reversal in the boundary layer.展开更多
Using the high-resolution non-hydrostatic model ARPS （Advanced Regional Prediction System）, the Typhoon Rananim （0414） was simulated by using the CINRAD Doppler radar data. The results before and after typhoon lan...Using the high-resolution non-hydrostatic model ARPS （Advanced Regional Prediction System）, the Typhoon Rananim （0414） was simulated by using the CINRAD Doppler radar data. The results before and after typhoon landfall show that model ARPS performs well to simulate the track, the variation of center pressure, as well as severe heavy rain of Rananim. Meanwhile, the simulated composite reflectivity was compared with the observed radar composite reflectivity. The numerical results reveal that the asymmetrical structure of Rananim plays an important role in its westward deflecting after landfall. The sensitivity simulation experiments of terrain effects on Rananim （0414） were also investigated, and the terrain of the southeastern China has important effects on Rananim turning right slightly of its track and increasing its intensity obviously, but when typhoon is far away from the coastline, the terrain only impacts slightly on the storm intensity during its landfall. The results show that topographic lifting contributes greatly to precipitation enhancement, and makes the distribution of precipitation more uneven.展开更多
基金supported by the National Basic Research Program of China (2009CB421505)the National Natural Science Foundation of China under Grants Nos.40730948+5 种基金the National Natural Science Foundation of China under Grants Nos.40575030the National Natural Science Foundation of China under Grants Nos.40705024the Shanghai Typhoon Foundation (2009ST09)supported by the National Nature Science Foundation of China under the Grant No.40675060the program of the Ministry of Science and Technology of the People's Republic of China (2006AA09Z151)the program of China Meteorological Administration(GYHY200706031)
文摘Finescale spiral rainbands associated with Typhoon Rananim （2004） with the band length ranging from 10 to nearly 100 km and band width varying from 5 to 15 km are simulated using the Fifth-Generation NCAR/Penn State Mesoscale Model （MM5）. The finescale rainbands have two types： one intersecting the eyewall and causing damaging wind streaks, and the other distributed azimuthally along the inner edge of the eyewall with a relatively short lifetime. The formation of the high-velocity wind streaks results from the interaction of the azimuthal flow with the banded vertical vorticity structure triggered by tilting of the horizontal vorticity. The vertical advection of azimuthal momentum also leads to acceleration of tangential flow at a relatively high Mtitude. The evolution and structures of the bands are also examined in this study. Further investigation suggests that the boundary inflection points are related tightly to the development of the finescale rainbands, consistent with previous findings using simple symmetric models. In particular; the presence of the level of inflow reversal in the boundary layer is a crucial factor controlling the formation of these bands. The near-surface wavy peaks of vertical vorticity always follow the inflection points in radial flow. The mesoscale vortices and associated convective updrafts in the eyewall are considered to strengthen the activity of finescale bands, and the updrafts can trigger the formation of the bands as they reside in the environment with inflow reversal in the boundary layer.
基金Supported by the Meteorology Gathers Capital Plan Key Project of Zhejiang Province under Grant Nos.2004ZD03,2004ZD05,and the Technical Plan Key Project of Wenzhou under Grant No.S2003A011.
文摘Using the high-resolution non-hydrostatic model ARPS （Advanced Regional Prediction System）, the Typhoon Rananim （0414） was simulated by using the CINRAD Doppler radar data. The results before and after typhoon landfall show that model ARPS performs well to simulate the track, the variation of center pressure, as well as severe heavy rain of Rananim. Meanwhile, the simulated composite reflectivity was compared with the observed radar composite reflectivity. The numerical results reveal that the asymmetrical structure of Rananim plays an important role in its westward deflecting after landfall. The sensitivity simulation experiments of terrain effects on Rananim （0414） were also investigated, and the terrain of the southeastern China has important effects on Rananim turning right slightly of its track and increasing its intensity obviously, but when typhoon is far away from the coastline, the terrain only impacts slightly on the storm intensity during its landfall. The results show that topographic lifting contributes greatly to precipitation enhancement, and makes the distribution of precipitation more uneven.
