近海台风中心自适应定位方法研究

An algorithm for adaptive identifying and tracking eyes of typhoons near landfall

本研究提出了近海台风自适应定位方法(typhoon eye adaptive identifying and tracking,TEAIT).该方法主要基于多普勒反射率数据对近海台风的台风眼进行客观的识别和追踪.文中对4个典型台风个例使用TEAIT方法进行了定位测试,并将其与基于径向风的GBVTD-simplex和基于弱回波的TCET方法作比较.相比GBVTDsimplex方法,因为雷达回波的观测半径要大于径向风,TEAIT方法可以更早的追踪台风.对相同时段定位比较表明,两者中心定位差绝大部分都分布在5km内.进一步分析表明,差异大主要是在台风路径显著转向或者台风眼剧烈收缩时,此时台风环流中心和回波中心不重合导致.相比同样基于回波的TCET方法,TEAIT方法即便在台风结构不对称、眼不闭合、低层填塞等情况下都能成功定位,而TECT法在这些情形下容易定位失败.TEAIT方法比TECT方法表现出更好地识别和连续追踪能力.

In this study,a typhoon eye adaptive identifying and tracking（TEAIT）algorithm which based on radar re-flectivity is developed to obj ectively identify and track the center of typhoon near the coast.Four typical typhoon cases were selected to examine the performance of this method and the results were compared through two operational methods：the GBVTD-simplex（ground-based velocity-track-display）and the TCET（tropical cyclone eye tracking）.The former is based on radar radial while the latter is based on weak echo.Since the observation range of reflectivity is larger than radial wind,TEAIT can track typhoon center earlier than GBVTD-simplex.The comparison in the same track period indicates the difference between those two methods is small.Most of center differences are within 5 km.The significant difference was found in the moment when the structure of the typhoon eye changes rapidly.In that case,the center of the wind field is not consistent with the center of reflectivity.Compared to the TCET algorithm which is also reflectivity-based method,the TEAIT algorithm can track the center even in the situation when the structure of typhoon is asymmetrical,or the eye is not closed,or the low level is filled due to the landing process and so on.In contrast,TCET may failed to locate the center in those circumstances.TEAIT can track the center more steadily and continuously than TCET.