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台风“杜苏芮”(2305)残涡特大暴雨的多模式预报性能比较分析

Comparison of the performance of multiple operational models on prediction of heavy rain caused by residual vortex of Typhoon Doksuri (2305)

  • 摘要: 2023年7月29日至8月1日,受“杜苏芮”残余环流影响,华北地区发生特大暴雨。本文就此次降水事件,对包括欧洲中期天气预报中心业务预报系统(EC-IFS)、美国国家环境预报中心全球数值天气预报系统(NCEP-GFS)和中国气象局全球同化预报系统(CMA-GFS)在内的三个业务模式在不同时效的预报性能进行了评估,并分析了偏差产生的可能原因。研究表明:(1)三个模式均能提前48小时准确预报此次暴雨事件,预报能力整体随预报时效增加而降低,EC-IFS性能相对最优,预报时效24~120 h平均空间相关系数(SCC)大于0.5,NCEP-GFS 24~48 h时效SCC接近EC-IFS,72 h后明显降低且波动较大,CMA-GFS平均SCC在72 h后则降为负值。(2)在落区形态方面,EC-IFS与观测最为接近,能较好再现暴雨的东北—西南走向;NCEP-GFS落区偏南,其原因在于副高偏东,导致南风偏弱;CMA-GFS预报的降水落区偏东,是由于副高偏东的同时大陆高压偏西,残涡得以北上所致。在降水强度方面,三个模式均存在强降水极值的低估。(3)非绝热加热垂直结构表明,模式预报性能的差异主要源于模式物理过程参数化的不确定性。几乎所有模式都无法准确模拟出与观测一致的降水—?相对湿度倾斜增湿结构,表明模式在对流、云等次网格物理过程参数化方面的不足是引起模式预报偏差的主要原因。

     

    Abstract: Due to the residual circulation of Typhoon Doksuri (2305), heavy rainstorm events occurred in North China during July 29 to August 1, 2023. This study evaluated the performance of three operational models at varying forecast lead time, including the Integrated Forecast System of European Centre for Medium-Range Weather Forecasts (EC-IFS), the Global Forecast System of National Centers for Environmental Prediction (NCEP-GFS) and the China Meteorological Administration Global Forecast System (CMA-GFS). The possible causes of the forecast biases are also analyzed. Results show that: (1) The forecast capability of the three models decreases with the increasing forecast lead time. Among all, EC-IFS outperforms the other two models with averaged spatial correlation coefficient (SCC) over 0.5 at lead time 24-120 h, SCC of NCEP-GFS approximates EC-IFS when leads 24-48 h but significantly decreases and fluctuates after 72 h, whereas that decreases to negative values in CMA-GFS. (2) In terms of rainfall location, EC-IFS well reproduced the distribution pattern of the heavy rain, while the forecasted rainfall in NCEP-GFS locates to the south of the heavy rain due to the eastward location of the forecasted subtropical high and weakened south flow; CMA-GFS predicts rainfall noticeably eastward, which is mainly caused by shifted subtropical high and continental high, allowing the residual vortex to move northward. As for intensity, all three models commonly underestimated the extreme value of heavy precipitation. (3) Vertical structures of diabatic heating indicate that the difference of model performance is mainly due to the uncertainties of parameterization for model physical process. Almost all models are unable to accurately simulate the precipitation-relative humidity tilting structure as in observation, implying that models still have deficiencies in parameterizing sub-grid physical processes such as convection and clouds, which are the main causes of model forecast bias.

     

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