Rao Jian, Garfinkel Chaim I, White Ian P
Fredy & Nadine Herrmann Institute of Earth Sciences The Hebrew University of Jerusalem Jerusalem Israel.
Key Laboratory of Meteorological Disaster, Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and Technology Nanjing China.
J Geophys Res Atmos. 2020 Jan 27;125(2):e2019JD031919. doi: 10.1029/2019JD031919. Epub 2020 Jan 22.
Using the real-time predictions from 11 models, this study analyzes the prediction of the downward propagation and surface impact of the 2018 and 2019 sudden stratospheric warmings (SSWs). These two SSWs differed both in their morphology types (2018: split; 2019: displacement followed by split) and magnitudes (the former being stronger). With a large sample size (>2,200) of multimodel ensemble forecasts, it is revealed that the strength of the SSW is more important than the vortex morphology in determining the magnitude of its downward impact, with strong SSWs more likely to propagate downward than weak SSWs. Therefore, based on the probabilistic forecasts, the observed strong SSW in February 2018 was more likely to have a downward and surface impact than the January 2019 SSW. The relationship between the 10-hPa dominant wave number and the 100-hPa polar cap height (or the Northern Annular Mode) is weak, implying that the dominant wave number might not be the primary factor determining the downward propagation of SSWs in the two analyzed cases. Hence, the high polar cap height (or negative Northern Annular Mode) response in the lower stratosphere and troposphere following the February 2018 SSW is mainly attributed to its strong intensity rather than the split morphology. Further, the 2-m temperature anomaly pattern following the January 2019 SSW is not forecasted due to its weak downward propagation, whereas the 2-m temperature in North Eurasia, Middle East, south China, and eastern United States could be forecasted for the downward propagating February 2018 SSW. However, regional rainfall anomalies are poorly forecasted (both in a deterministic and probabilistic sense) for both SSWs.
本研究利用11个模型的实时预测结果，分析了2018年和2019年平流层突发性增温（SSW）的向下传播及对地表影响的预测情况。这两次平流层突发性增温在形态类型（2018年：分裂型；2019年：先位移后分裂型）和强度（前者更强）上均有所不同。通过多模型集合预报的大样本量（>2200）发现，在确定平流层突发性增温向下影响的程度时，其强度比涡旋形态更为重要，强平流层突发性增温比弱平流层突发性增温更有可能向下传播。因此，基于概率预报，2018年2月观测到的强平流层突发性增温比2019年1月的平流层突发性增温更有可能产生向下及对地表的影响。10百帕主导波数与100百帕极帽高度（或北半球环状模）之间的关系较弱，这意味着在这两个分析案例中，主导波数可能不是决定平流层突发性增温向下传播的主要因素。因此，2018年2月平流层突发性增温之后，平流层下部和对流层出现的高极帽高度（或负北半球环状模）响应主要归因于其强强度，而非分裂形态。此外，由于2019年1月平流层突发性增温向下传播较弱，因此未对其之后的2米温度异常模式进行预报，而对于向下传播的2018年2月平流层突发性增温，可以对欧亚大陆北部、中东、中国南方和美国东部的2米温度进行预报。然而，对于这两次平流层突发性增温，区域降雨异常的预报效果都很差（无论是确定性预报还是概率预报）。
