热带气旋路径集合预报试验

Ensemble Prediction Experiments of Tropical Cyclone Track

以MM5模式为试验模式,分别用增长模繁殖法(BGM)和模式物理过程扰动法(MPP)形成12个集合成员,对2005年登陆我国的8个热带气旋进行了52次路径集合预报试验,以寻找适合西北太平洋热带气旋路径的集合预报方法。结果表明:BGM方法的集合预报结果总体上好于控制试验结果,其中对强度较弱的热带气旋的集合预报效果更好。MPP方法的集合预报结果总体上不如控制试验结果,但对初始时刻强度达到台风的热带气旋的集合预报效果较好,集合预报相对于控制试验的改进效果明显。基于BGM方法和MPP方法集合预报的不同特点,将两种方法相结合形成扰动成员,这一综合方法的集合预报效果好于单一方法的集合预报效果。BGM方法和MPP方法的系统发散度总体上都偏小。

In order to find the ensemble prediction method that can be used to forecast the tracks of tropical cyclones in the Western North Pacific Ocean, 52 cases tropical cyclone track ensemble prediction experiments are made, the 52 cases are from the 8 tropical cyclones that made landfall at China in 2005. MM5 model is used as the experiment model. The model has a horizontal grid spacing of 45 km with 115 × 115 points and 23 vertical sigma layers. It is run for 72 h. The model domain center is same as the center of ex- periment tropical cyclone. There are 12 ensemble members. 12 members consist of 11 perturbation members and a control forecast. Two methods are used to create the perturbation members. One method is breeding of growing modes （BGM）, in which two 12-h breeding cycles are carried out. The other method is model physics perturbation （MPP）, in which members are created by choosing different physics parameterization schemes. The experiment results show that the ensemble mean of BGM is better than the control forecast and the ensemble mean of MPP is worse than the control forecast. For BGM, the ensemble mean for the tropical cyclones whose initial intensity is smaller than 32.6 m/s is more skillful than the ensemble mean for the tropical cyclones whose initial intensity is larger than 32.6 m/s. For MPP, the ensemble mean for the tropical cyclones whose initial intensity is larger than 32.6 m/s is better than the control forecast. According to the different results of BGM ensemble and MPP ensemble, a new method is used to create the perturbation members. In this new method, when the initial intensity of tropical cyclone is smaller than 32.6 m/s, BGM method is used to create the perturbation members, when the initial intensity of tropical cyclone is larger than 32.6 m/s, both BGM method and MPP method are used to create the perturbation members. The ensemble mean of this method is better than the ensemble mean of BGM or MPP. The spreads of BGM ensemble, MPP ensemble and the new method are all too small.