【摘要】 台风“海葵”（2012）受鞍型场影响，在安徽南部维持少动，引发极端降水。为了探究“海葵”进入鞍型场后，其路径及降水预报对模式初始场的敏感性，基于WRF(Weather Research&Forecasting)模式和集合卡尔曼滤波（EnKF,Ensemble Kalman Filter）同化系统，对“海葵”开展了集合预报试验和敏感性试验。结果表明：（1）“海葵”登陆浙江西北行进入安徽境内后，集合预报路径主要分为滞留型、转向东行型和西行型，其中滞留型路径与“海葵”观测路径基本一致。（2）与台风自身环流相比，初始条件中环境场的差异是导致试验中台风移动差异的关键因素。台风移动对初始场中西北模拟区域的大陆高压和中纬度低槽更加敏感。（3）当初始场中大陆高压和低槽强度相当时，减弱的台风环流一直处于大陆高压和副热带高压之间，导致台风在安徽南部停滞，并与冷空气相互作用在皖南-赣北产生强降水。而当初始场中大陆高压弱且低槽较强时，24 h预报中台风虽处于鞍型场中，但大陆高压与副热带高压均偏弱。随着低槽南下，大陆高压减弱西退，副热带高压位置偏东，导致台风转向东北行，在江苏境内产生强降水；反之，当大陆高压强但低槽较弱时，台风持续西行，冷空气受高压阻挡未能直接影响台风降水，导致皖南地区降水相对偏弱。更多还原

【Abstract】 Typhoon Haikui(2012) was influenced by a saddle-point flow field, resulting in nearly stationary movement in southern Anhui and causing extreme rainfall. To examine the sensitivity of the track and precipitation forecast of Haikui to the model’s initial conditions after entering the saddle-point region, ensemble forecast experiments and sensitivity experiments were conducted for Haikui using the Weather Research & Forecasting(WRF) model coupled with an Ensemble Kalman Filter(EnKF)assimilation system. The results show that:(1) After Typhoon Haikui made landfall in Zhejiang and moved northwestward into Anhui, typhoon tracks forecast by ensemble forecasting experiments can mainly be divided into the stagnation type, the eastward-turning type, and the westward-moving type. The stagnation tracks are most similar to the observed track of Haikui.(2) Compared with the circulation of the typhoon itself, differences in the environmental field of initial conditions are the key factor causing variations in typhoon motion in the experiments. The typhoon’s movement is more sensitive to the continental highpressure system and mid-latitude trough in the northwestern part of the simulation domain.(3) When the intensities of the continental high and trough are comparable in the initial field, the weakened typhoon circulation remains between the continental high and the subtropical high, leading to stagnation over southern Anhui. This, combined with cold air interaction, results in heavy rainfall in southern Anhui and northern Jiangxi. When the continental high is weak and the trough is strong in the initial field, the typhoon is forecasted to be in a saddle-point field in the 24-hour forecast. However, both the continental high and the subtropical high are relatively weak. As the trough moves southward, the continental high weakens and retreats westard, and the subtropical high shifts eastward. The typhoon then turns northeastward, resulting in heavy rainfall in Jiangsu. Conversely, when the continental high is strong but the trough is weak, the typhoon continues moving westward. The influence of the trough and cold air shifts to the north. Cold air is blocked by the high pressure and fails to directly interact with the typhoon’s circulation, resulting in relatively weaker precipitation in southern Anhui.更多还原