A high-resolution simulation of Typhoon Saomai (2006)：Low layer wind profile around its landing

In this study, the typhoon case of Saomai (2006) is well reproduced using the WRF-ARW system with a finest horizontal resolution of 1 km and vertical resolution of 40-model levels in which the lower levels are densified. Based on the 1 km simulated data of Typhoon Saomai (2006), the wind structure in the lower levels (below 1500 m height over sea level or terrain) over the typhoon are analyzed. The strong vertical shear of horizontal wind speed is found near the radius of maximum wind (RMW) during the typhoon staying over sea. Two shear factors for the high levels and low levels, respectively, are defined. And then vertical profiles of horizontal wind speed are categorized into four types according to the two shear factors, two of which are stronger in shear and belong to jet type profiles. Further, their locations in the typhoon and the jet heights for the four type vertical profiles of horizontal wind are analyzed. And the possible causes of generating the two jet type profiles are also analyzed and discussed. The results show the changes of supergradient/subgradient wind in the vertical direction should be responsible for the jet type profiles and the advection of angular momentum plays an important role in it. However, no jet type profile is found after the typhoon landed.