EAPSI: Investigating the Influence of the Madden-Julian Oscillation on Northern Hemisphere Winter Blocking in General Circulation Models

阻塞是指一种大规模的准静止高压，一次可以持续长达数周，导致冬季突然出现长时间的寒流和极端降水。 了解气候变化中的极端天气需要了解气候变化中的阻塞。 这是使用大气环流模型（GCM）完成的，该模型使科学家能够改变温室气体，以了解对大气现象可能产生的后果。 研究表明，在大气环流模型中对阻塞的模拟很差，导致阻塞偏差，并对极端事件产生影响。 该奖项支持研究，以了解是否可以通过改进模型Madden-Julian Oscillation（MJO）来减少GCM中的阻塞偏差。 MJO的特点是向东传播的对流异常发射大尺度大气波，影响高纬度地区的阻塞。 本研究将与韩国首尔的首尔国立大学的对流层外动力学专家Seok-Woo Son博士合作，调查MJO对模型阻塞的影响。研究假设，为了改善模型阻塞，除了模型基本状态之外，还必须改善模型MJO，这决定了MJO引起的Rossby波影响阻塞的路径。 该假设将通过分析和比较耦合模型相互比较项目（CMIP 5）第五阶段内的六个GCM来进行测试，其中三个模拟了相当现实的MJO，三个模拟了由MJO工作组诊断确定的较差的MJO。 MJO相位将通过将模型数据投影到再分析导出场的主导模式上来导出，并将使用波活动通量分析来分析Rossby波路径。 将按照MJO阶段计算模型阻塞频率，并将结果与再分析进行比较。 然后，将使用结果来了解模型MJO如何有助于阻塞偏倚。这个NSF EAPSI奖是与韩国国家研究基金会合作资助的。

Blocking refers to a large-scale quasi-stationary high pressure that can persist for up to weeks at a time, leading to sudden long-lasting cold snaps and precipitation extremes during winter. Understanding weather extremes in a changing climate requires understanding blocking in a changing climate. This is done using General Circulation Models (GCMs), which allow scientists to alter greenhouse gases to understand the possible consequences to atmospheric phenomena. Studies have shown that blocking is poorly simulated in GCMs, resulting in blocking biases with consequences for extreme events. This award supports research to understand if blocking biases in GCMs can be reduced by improving the model Madden-Julian Oscillation (MJO). The MJO is characterized by eastward propagating convective anomalies emitting large-scale atmospheric waves that impact blocking at higher latitudes. The research will investigate how model blocking is influenced by the model MJO in collaboration with Dr. Seok-Woo Son, a specialist in extratropical dynamics, at Seoul National University in Seoul, South Korea.The research hypothesizes that in order to improve model blocking, the model MJO must be improved in addition to the model basic state, which determines the pathway of the MJO-induced Rossby waves that impact blocking. The hypothesis will be tested by analyzingand comparing between six GCMs within the Fifth phase of the Coupled Model IntercomparisonProject (CMIP5), where three simulate a fairly realistic MJO and three a poor MJO as determined by diagnostics of the MJO Task Force. MJO phases will be derived by projecting model data onto the leading patterns of reanalysis-derived fields, and the Rossby wave pathway will be analyzed using wave activity flux analysis. Model blocking frequencies will be calculated per MJO phase, and results will be compared to reanalysis. Results will then be used to understand how the model MJO may contribute to blocking biases. This NSF EAPSI award is funded in collaboration with the National Research Foundation of Korea.