一种非对称台风Bogus方法的数值模拟应用

Numerical simulation application of an asymmetrical typhoon bogus scheme

前人研究中BDA方法采用的轴对称Bogus台风不能反映个别台风具体特征,也弃掉了背景场的合理成分,有必要改用更精细的非对称台风Bogus模型对BDA方案做出改进。因此,提出一种充分融合分析场信息和实际观测信息并考虑副高影响的非对称台风Bogus方法,针对0613、0704台风个例,通过4DVAR技术,利用MM5模式及其伴随模式对此Bogus资料进行BDA同化试验和模拟预报,数值结果表明:BDA方法同化非对称台风Bogus模型,其路径预报效果优于同化轴对称台风模型,同化两种Bogus资料都使台风强度模拟效果得到极大改善,但改善程度相当,故台风的非对称结构及副高等外围环境场及背景场弱台风中合理信息对台风的准确模拟起到关键作用,同时,Bogus资料同化方法用于远洋上的台风时,需注意台风模型与副高的配置关系。

An axisymmetric bogus vortex at sea level was used in the traditional bogus data assimilation （BDA） scheme. This vortex could not accurately describe the specific characteristics of typhoon.The reasonable elements of the background field were discarded also. It is necessary to switch to a more sophisticated asymmetric bogus typhoon to make improvements for BDA. Thus,an asymmetrical typhoon bogus method with blend information from the analysis and the observation is brought forward while the impact of the subtropical anticyclone is considered as well.With the fifth-generation Penn State/NCAR Mesoscale Model （MM5） and its adjoint model,the four dimensional variatiaonal data assimilation （4DVAR） technique is employed to build a BDA scheme to assimilate this asymmetrical bogus vortex. The track and intensity of NO.0613 and NO.0704 typhoon are simulated. The results show that,the improvement of track simulation using new bogus data is more significant than that using Symmetrical Bogus data. The intensity forecasts are greatly improved by using both two kinds of bogus data,and the improvements are in a nearly same degree. Therefore,the non-symmetrical structure of typhoon,the rational element of the weak typhoon in the background field,the subtropical anticyclone,and other external environment field,play a key role in accurate simulation of typhoons. At the same time,when BDA method is used for ocean-going typhoon,it needs to pay attention to the configuration of the relationship between the subtropical and bogus typhoon model.