超强台风“桑美”(0608)近海观测特征研究

Observational Features of Super Typhoon Saomai(2006) over Coastal Water of China

利用气象现代化手段观测的数据进行分析。从风云2C红外云图可以发现,在近海"桑美"台风强度加强过程中,台风外围云系被台风外核区吸收,风暴直径明显减小,结构更为密实,台风眼由模糊发展为清晰;在迅速加强阶段,台风迅速向内收缩,呈现眼壁上螺旋雨带的发展特征。根据温州新一代天气雷达CINRAD/SA的组合反射率和径向速度产品揭示了直到登陆前1 h,桑美台风的强度仍在加强的事实,从组合反射率可见,台风从单眼壁发展成双眼壁,之后发展成具备更加深厚眼壁的台风结构,此过程对应于雷达径向速度图表现为,从一个大速度区发展为二个大速度区,直至更大的速度区。从登陆前后几小时地面测站的变压计算气压梯度可以判断强风区大小,结合变压及小时极大风风向变化可判断登陆点,以及作出登陆后移动路径的短时预报;小时累计降水分布表明,其具有明显不对称分布特征,前进方向右侧大于左侧,强降水主要集中在台风环流主体区,外围降水不明显。

Typhoon Saomai （0608） is the strongest typhoons landed in China mainland nearly 50 years,which is characterized by very low central pressure, very great wind speed, particularly concentrative precipitation and energy, rapid development,fast movement and so on. It has a particularly strong destructive power in the energy concentration area, which is irresistible and cause direct economic losses over 111 billion Yuan in Zhejiang and Fujian provinces because its intensity is extremely strong. Thus, it is very significant to analyse observational features and causes of explosive development of super typhoon Saomai （2006） over coastal water of China. This paper takes full advantage of meteorological observations from modern means. FY-2C infrared images show that,in the process of typhoon Saomai strengthening, the typhoon outer clouds was absorbed by the typhoon outer core region with the significantly reduced storm diameter,more dense structure, and the clear typhoon eye developed from the fuzzy one. In the rapid strengthening phase ,the typhoon rapidly shrink inward with a concentric eyewall structure and development characte~ of deep-wall convective cloud spiral rain band. Based on the echo data （composite reflectivity and radial velocity） observed by the new generation weather radar CINRAD/SA in Wenzhou,we can find the fact that the typhoon is still strengthened until 1-hr before landing. From the composite reflectivity data,we can see that the typhoon eye developed from a single eyewall into a double one, sub- sequently developed into one with more profound eyewall,which is corresponding to a development process,i.e, from a high speed area to two high speed areas,until to a higher speed area shown in the radar radial velocity map. Based onthe 3-hr pressure variation of auto weather stations ,we can judge the strong wind velocity by calculating the surface pres- sure gradient before and after landing. By combining the pressure gradient and hourly direction change of maximum wind,we can decide the landing point and do a short-term forecasting on the moving path after landing. The hourly accu- mulated rainfall distribution shows that it has an apparent asymmetry feature, and the rainfall on the right side of typhoon advancing direction is larger than that on the left one, going with the heavy precipitation mostly concentrated in the main region of typhoon circulation and without the obvious external precipitation.