基于对流尺度集合模拟的长江中下游暖区对流过程的可预报性研究  

Predictability Study ofWarm-sector Convective Event over the Middle-lower Reaches of the Yangtze River:Based on Convection-allowing Ensemble Simulation

作　　者：徐渊 闵锦忠[1] 庄潇然 XU Yuan;MIN Jinzhong;ZHUANG Xiaoran(Key Laboratory,Meteorological Disaster of Ministry of Education(KLME)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science&Technology,Nanjing 210044,Jiangsu,China;Jiangsu Meteorological Observatory,Nanjing 210008,Jiangsu,China)

机构地区：[1]南京信息工程大学气象灾害教育部重点实验室/气象灾害预报预警与评估协同创新中心,江苏南京210044 [2]江苏省气象台,江苏南京210008

出　　处：《高原气象》2022年第3期684-697,共14页Plateau Meteorology

基　　金：国家重点研发计划项目(2017YFC1502103);国家自然科学基金重点资助项目(41430427)。

摘　　要：弱天气尺度强迫背景下的暖区暴雨发生发展机制复杂且难以准确预报。为深入探讨长江中下游暖区对流过程的实际和内在可预报性,本文通过同化模式模拟的探空、雷达等仿真资料的集合资料同化,构建了基于WRF-EnSRF的对流尺度集合预报系统,针对2013年7月21日一次典型暖区对流过程进行了初值扰动集合试验。试验结果表明,不同成员降水预报的发生时间和落区存在两个有显著差异的分岔时段,其一在对流触发阶段,源于扰动风场与地形的相互作用;其二在发展阶段,源于初值扰动导致对流系统强度出现差异,对流强(弱),冷池出流强(弱),导致降水落区偏南(北)。进一步的可预报性定量分析可见,由于初值的扰动,在分岔时段,模式的实际可预报性受到严重限制,表现为集合成员降水场的差异和扰动的偏差能量均快速增大。同时,在减小扰动振幅的“等同孪生子”对比试验中,扰动偏差能量随时间变化的曲线在对流触发阶段表现出的非线性特征表明,内在可预报性在这一分岔时段也显著受限。由以上结果可进一步得出结论:由于初值扰动导致分岔时段模式的实际可预报性受限时,准确的初值可有效改进预报效果。而当系统受到由混沌非线性动力学所导致的内在可预报性限制时,改善初值预报效果有限,须进一步考虑采用集合(概率)预报。上述研究对于理解长江中下游暖区对流过程的可预报性,以及针对相应的分岔特征发展适合于对流尺度的集合扰动方法或建立目标观测具有一定的参考价值。Warm-sector torrential rainfall event under the background of weak synoptic-scale forcing is difficult to predict accurately due to less knowledge on its initiation and development mechanism.In order to further investigate the practical and intrinsic predictability of warm-sector convective event over the middle-lower reaches of the Yangtze River(MLRYZ),a convection-allowing ensemble forecast(CaEF)system based on WRF-EnSRF is constructed by using ensemble data assimilation which assimilates the radiosonde and radar simulation data simulated from the convection-allowing model.An initial perturbation ensemble experiment is conducted for a typical warm-sector convective event on 21 July 2013,and the experimental results show that there are two bifurcation stages with significant differences in convection initiation time and precipitation location among ensemble members.The first bifurcation is related to interaction between perturbed planetary boundary layer wind field and mesoscale topography in convection initiation stage,while the second in convection development stage is due to the difference of convective system intensity caused by initial perturbations.Strong(weak)convection and strong(weak)outflow from cold pool could lead to a south(north)precipitation area.Further predictability analysis based on quantitative method suggests that the practical predictability at bifurcation stages is strongly limited reflected by rapid growth in precipitation field variation(both time and space)and difference total energy(DTE).Additionally,nonlinear characteristic between difference total energy curves in identical-twin experiments reducing the amplitude of initial perturbations reveals a more serious limit of intrinsic predictability during convection initiation stage(the first bifurcation stage)than other times.The significant sensitivity mode on ensemble sensitivity analysis(ESA)also shows that the error of planetary boundary layer wind field has an important influence on both practical and intrinsic predictability in thi

关 键 词：对流尺度集合模拟 暖区对流过程 实际可预报性 内在可预报性 

分 类 号：P456.7[天文地球—大气科学及气象学]