The precipitation during landfall of typhoon Haitang(2005) showed asymmetric structures(left side/right side of the track). Analysis of Weather Research and Forecasting model simulation data showed that rainfall on the right side was more than 15 times stronger than on the left side. The causes were analyzed by focusing on comparing the water vapor flux,stability and upward motion between the two sides. The major results were as follows:(1) Relative humidity on both sides was over80%,whereas the convergence of water vapor flux in the lower troposphere was about 10 times larger on the right side than on the left side.(2) Both sides featured conditional symmetric instability [MPV(moist potential vorticity) <0],but the right side was more unstable than the left side.(3) Strong(weak) upward motion occurred throughout the troposphere on the right(left) side. The Q vector diagnosis suggested that large-scale and mesoscale forcing accounted for the difference in vertical velocity. Orographic lift and surface friction forced the development of the asymmetric precipitation pattern. On the right side,strong upward motion from the forcing of different scale weather systems and topography caused a substantial release of unstable energy and the transportation of water vapor from the lower to the upper troposphere,which produced torrential rainfall. However,the above conditions on the left side were all much weaker,which led to weaker rainfall. This may have been the cause of the asymmetric distribution of rainfall during the landfall of typhoon Haitang.
Based on the data(including radius of maximum winds) from the JTWC(Joint Typhoon Warning Center),the tropical cyclones(TCs) radii of the outermost closed isobar, TCs best tracks from Shanghai Typhoon Institute and the Black Body Temperature(TBB) of the Japanese geostationary meteorological satellite M1 TR IR1, and combining13 tropical cyclones which landed in China again after visiting the island of Taiwan during the period from 2001 to2010, we analyzed the relationship between the number of convective cores within TC circulation and the intensity of TC with the method of convective-stratiform technique(CST) and statistical and composite analysis. The results are shown as follows:(1) The number of convective cores in the entire TC circulation is well corresponding with the outer spiral rainbands and the density of convective cores in the inner core area increases(decreases) generally with increasing(decreasing) TC intensity. At the same time, the number of convective cores within the outer spiral rainbands is more than that within the inner core and does not change much with the TC intensity. However, the density of convective cores within the outer spiral rainbands is lower than that within the inner core.(2) The relationship described above is sensitive to landing location to some extent but not sensitive to the structure of TC.(3) The average value of TBB in the inner core area increases(decreases) generally with increasing(decreasing) of TC intensity, which is also sensitive to landing situation to some extent. At the same time, the average value of TBB within the outer spiral rainbands is close to that within the entire TC circulation, and both of them are more than that within the inner core. However, they do not reflect TC intensity change significantly.(4) The results of statistical composite based on convective cores and TBB are complementary with each other, so a combination of both can reflect the relationship between TC rainbands and TC intensity much better.
