LAUSR

This study reports verification results of hindcast data of four systems in the subseasonal-to-seasonal (S2S) prediction project for major stratospheric sudden warmings (MSSWs) in northern winter from 1998/99 to 2012/13. This report deals with average features across all MSSWs, and possible differences between two MSSW types (vortex displacement and split types). Results for the average features show that stratospheric forecast verifications, when further averaged among the four systems, are judged to be successful for lead times around 10 d or shorter. All systems are skillful for lead times around 5 d, whereas the results vary among the systems for longer lead times. A comparison between the MSSW types overall suggests larger forecast errors or lower skill for MSSWs of the vortex split type, although the differences do not have strong statistical significance for almost all cases. This limitation is likely to at least partly reflect the small sample size of the MSSWs available. 基于回报试验结果, 本研究对四个预报系统进行的 1998/99-2012/13 年冬季北半球平流层爆发性增温 (MSSWs) 的次季节至季节预报方案进行了验证. 本研究讨论了所有 MSSWs 的平均特征, 以及两种 MSSWs 类型 (极涡位移型和极涡分裂型) 之间可能存在的差异. 平均特征表明, 当对四个系统的结果进行平均处理时, 可以成功地超前 10 天或更短一点时间的预报 MSSWs. 另外, 每个系统超前 5 天的预报技巧都很高, 但是对于更长的预报时间, 各个系统的预报能力有所不同. 对比不同类型的 MSSWs 的预报结果发现, 对极涡分裂型 MSSWs 的预报会存在较大误差并且预报技巧较低. 所有事件中这些差异在统计检测中并不显著, 这种差异的不显著可能与个例太少有很大的关系.