AMSU-A全空辐射率资料同化对台风“天鸽”的预报影响研究

The impact of AMSU-A all-sky data assimilation on the forecast of super typhoon HATO

利用美国NCEP(National Centers for Environmental Prediction)发展的GSI(Gridpoint Statistical Interpolation)同化系统和GSM(Global Spectral Model)全球频谱预报模式作为循环同化系统,选用2017年第13号台风为研究个例,采用全空和晴空两种同化方案对AMSU-A(The Advanced Microwave Sounding Unit-A)辐射率观测开展同化对比试验,并对台风“天鸽”个例进行5 d预报,研究AMSU-A全空辐射率同化对台风天鸽发展过程预报的影响。结果表明,全空同化方案相比晴空同化方案预报的台风路径、台风中心气压以及台风最大风速预报误差更小;全空同化方案对台风“天鸽”生命周期的模拟更加准确,更接近中国气象局发布的台风天鸽最佳路径的最低气压,而晴空同化方案预报的台风发展较弱,无法预报出成熟期的台风强度;全空同化方案能够增加低层通道海上厚云覆盖区域辐射率资料同化量,增幅占AMSUA同化观测总量10%,从而改进海洋区域天气系统的热力场结构。

By using the GSI (Gridpoint Statistical Interpolation) assimilation system developed by NCEP (National Centers for Environmental Prediction) and the global spectrum prediction model of GSM (Global Spectral Model) as the cyclic assimilation system,the thirteenth typhoon in 2017 was selected for a case study.The two assimilation schemes of all sky and clear sky were used to make assimilation comparison test on AMSU-A (The Advanced Microwave Sounding Unit-A) radiance observation,and the authors implemented 5-day forecast on typhoon “HATO” to study the impact of AMSU-A full-sky radiance assimilation on the development of typhoon HATO.The results showed that errors in typhoon path,typhoon center pressure and typhoon s maximum wind speed predicted by the all-sky assimilation scheme were smaller than those by the clear-sky assimilation scheme.The full-sky assimilation scheme was more accurate in the simulation of typhoon HATO s life cycle,and it was closer to the lowest pressure of the best path of the typhoon released by China Meteorological Administration.The result forecasted by the clear sky assimilation scheme was weaker and the typhoon intensity at its mature stage could not be predicted.The full-sky assimilation scheme could increase the thick cloud coverage area of the low-level passage.The amount of radiance data assimilation increased by 10% of the total amount of AMSUA assimilation observations,and thereby improved the thermal field structure of the weather system in the marine area.