The occurrence of a Ural blocking (UB) event is an important precursor of severe cold air outbreaks in Siberia and East Asia, and thus is significant to accurately predict UB events. Using subseasonal to seasonal (S2S) models of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Environment and Climate Change Canada (ECCC), we evaluated the predictability of a persistent UB event on 18 to 26 January 2012. Results showed that the ECCC model was superior to the ECMWF model in predicting the development stage of the UB event ten days in advance, while the ECMWF model had better predictions than the ECCC model for more than ten days in advance and the decaying stage of the UB event. By comparing the dynamic and thermodynamic evolution of the UB event predicted by the two models via the geostrophic vorticity tendency equation and temperature tendency equation, we found that the ECCC model better predicted the vertical vorticity advection, ageostrophic vorticity tendency, the tilting effect, horizontal temperature advection, and adiabatic heating during the development stage, whereas the ECMWF model better predicted the three dynamic and the two thermodynamic terms during the decaying stage. In addition, during both the development and decaying stages, the two models were good (bad) at predicting the vortex stretching term (horizontal vorticity advection), with the PCC between both the predictions and the observations larger (smaller) than +0.70 (+0.10) Thus, we suggest that the prediction of the persistent UB event in the S2S model might be improved by the better prediction of the horizontal vorticity advection.

中文翻译：

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2012年1月在欧洲和加拿大的季节性至季节性模式下发生的强烈乌拉尔阻塞事件的可预测性

乌拉尔阻塞（UB）事件的发生是西伯利亚和东亚发生严重冷空气暴发的重要先兆，因此对于准确预测UB事件具有重要意义。我们使用欧洲中距离天气预报中心（ECMWF）和加拿大环境与气候变化中心（ECCC）的季节到季节（S2S）模型，评估了2012年1月18日至26日持续的UB事件的可预测性。结果显示在提前10天预测UB事件的发展阶段时，ECCC模型优于ECMWF模型，而提前10天以上和UB事件的衰减阶段，ECMWF模型比ECCC模型具有更好的预测。通过地转涡度趋势方程和温度趋势方程比较两个模型预测的UB事件的动态和热力学演变，我们发现ECCC模型更好地预测了垂直涡度对流，变质涡度趋势，倾斜效应，水平温度对流和绝热加热，而ECMWF模型可以更好地预测衰减阶段的三个动力学和两个热力学项。此外，在发育和衰变阶段，这两个模型在预测涡旋伸展项（水平涡度对流）方面都是好的（不好的），在预测和观测值之间的PCC大于（小于）+0.70（+ 0.10）因此，