台风“三巴”(2316)特大暴雨成因及预报偏差分析

Analysis of causes and forecast deviations of severe rainfall caused by Typhoon "Sanba"(2316)

基于常规气象观测资料、欧洲中期天气预报中心全球气候第五代大气再分析数据集(ERA5)、卫星、双偏振雷达观测资料和数值模式预报产品,对2316号秋季台风“三巴”造成广西特大暴雨的成因及预报偏差进行分析。结果表明:(1)高空辐散场和低空东南急流的卷入使台风“三巴”进入北部湾后强度增强,广西低层为相当位温大值区。冷空气的加入使得边界层东南急流和偏东气流在台风东北侧和北侧强烈汇合,造成了在冷垫之上的强辐合抬升运动,引发极端强降水。(2)台风“三巴”本体和倒槽旺盛发展的对流云团是造成特大暴雨的直接影响系统,桂东南到沿海上游地区不断有回波生成发展,形成明显的“列车效应”,雷达双偏振参量显示大暴雨落区低层存在明显的差分传播相移率(ZDR)和差分反射率因子(KDP)高值区。(3)数值模式对此次极端降雨较弱的预报能力,预报员对倒槽特大暴雨的对流特征、强度和持续时间认识的不足,导致预报员对冷空气主体南下速度预报偏快,对累积雨量的预报偏小。

Using conventional meteorological observation data,ERA5 reanalysis data,satellite data,dualpolarization radar observation data and numerical model products,the causes and forecast deviations of the extreme rainfall caused by Typhoon "Sanba"(No.2316) in the autumn in the Guangxi regionwere analyzed.The results showed that:(1)The combined effect of high-level divergence fields and low-level southeasterly jet streams strengthened Typhoon "Sanba" after it entered the Beibu Gulf.The lower layers of Guangxi are a significant region of high equivalent potential temperature.The inclusion of cold air made the boundary layer southeasterly jet and the easterly airflow converge strongly in the northeastern and northern sides of the typhoon,resulting in a strong convergence and uplift movement on top of the cold cushion,which caused extreme heavy precipitation in southeastern Guangxi.(2)The vigorous development of the main body of Typhoon "Sanba" and the inverted trough led to the formation of convective cloud clusters,directly influencing the occurrence of severe rainfall.Echoes continuously generated and developed in the upstream areas from southeastern Guangxi to the coastal regions,creating a distinct "train effect." Dual-polarization radar parameters displayed significant ZDR(differential reflectivity) and KDP(specific differential phase) high-value areas in the lower layer of the heavy rainfall region.(3)Insufficient understanding of the convective characteristics,intensity,and duration of the severe rainfall associated with the inverted trough,and the weak predictive capability of numerical models for extreme precipitation resulted in an overestimation of the southward speed of the cold air mass and an underestimation of the duration of the inverted trough's impact and a minor underestimation of cumulative rainfall forecasts by forecasters.