双台风相互作用及其影响

采用三维变分混合同化方法对双台风菲特（1323）和丹娜丝（1324）、天鹅（0907）和莫拉克（0908）进行数值模拟，并在此基础上，采用移除双台风中任一台风和增强或减弱任一台风的方法，对双台风的相互作用进行了敏感性试验。结果表明:台风丹娜丝的作用导致台风菲特路径偏南，移速偏慢；台风菲特的作用导致台风丹娜丝路径偏北，移速变化不大。双台风相互作用使台风菲特和丹娜丝强度发生变化。在台风菲特强盛阶段强度更强，减弱消亡阶段强度更弱。2013年10月6-9日我国华东地区出现的强降水主要受台风菲特影响，台风丹娜丝使降水强度增强、强降水中心位置偏南。双台风相互作用使台风天鹅移向偏南，移速偏快，但台风天鹅对台风莫拉克的移向、移速影响不大；台风天鹅路径盘旋曲折，每次移向的变化都与台风莫拉克有关；台风天鹅打转程度与台风莫拉克的强度呈正相关，双台风间存在涡度、水汽通量等的相互影响及输送机制。

Interaction and Influence of Binary Typhoons

The non-static mesoscale numerical model WRF V3.3 is used to study the influence of the interaction between binary typhoons on their moving path, intensity and precipitation. Data of NCEP FNL are used as initial field and side boundary conditions, and satellite data of ATOVS such as AMSUA, AMSUB, HIRS (3/4) are assimilated. Simulation results of binary typhoons in control runs, which are based on hybrid ensemble three-dimensional variational data assimilation (Ens-3DVar) system, are very close to the real intensity, moving path and precipitation. Beyond that, 6 sensitive experiments based on control runs are designed. The 96-hour simulations are conducted after one of the binary typhoons (Fitows/Danas/Goni/Morakot) is removed from the initial field which adopts the first step of vortex reconstruction technology in WRF ARW in the sensitive experiments (C1-RMF/C1-RMD/C2-RMG/C2-RMM). Experiment C2-WEM (C2-STM) is conducted by weakening or enhancing one of the binary typhoons in order to study effects of typhoon Morakot on typhoon Goni, but the typhoon radius is unchanged. Results of sensitive experiments and control runs are further compared and analyzed.
In Case 1, the role of typhoon Danas leads typhoon Fitow to move southward and slower. The role of typhoon Fitow causes typhoon Danas to move northward but has little effects on the shifting speed. The strength of binary typhoons Fitow and Danas have been changed by the interaction between them. Specifically, the interaction of binary typhoons makes the intensity of typhoon Fitow and typhoon Danas stronger in the strong stage and weaker in the dying stage of typhoon Fitow. From 6 October to 9 October in 2013, the heavy precipitation in East China is mainly affected by typhoon Fitow. Affected by typhoon Danas, the precipitation intensity brought by typhoon Fitow is enhanced, and the heavy precipitation center moves southward.
In Case 2, the interaction of binary typhoons makes typhoon Goni move southward and faster, but typhoon Goni has little influence on the movement and speed of typhoon Morakot. The winding path and direction change of typhoon Goni are all associated with typhoon Morakot. The bending extent of typhoon Goni is positively correlated with the strength of typhoon Morakot. Main causes are the interaction and transportation mechanism of vorticity, water vapor flux between binary typhoons.