Representation and Predictability of the East Asia-Pacific Teleconnection in the Beijing Climate Center and UK Met Offic
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Special Collection on Climate Science for Service Partnership (CSSP) China
OCTOBER 2020
Representation and Predictability of the East Asia–Pacific Teleconnection in the Beijing Climate Center and UK Met Office Subseasonal Prediction Systems Jie WU1, Peiqun ZHANG1*, Lei LI5, Hong-Li REN2,1, Xiangwen LIU1, Adam A. SCAIFE3,4, and Shuai ZHANG6 1 Laboratory for Climate Studies &China Meteorological Administration–Nanjing University Joint Laboratory for Climate Prediction Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China 2 State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing 100081, China 3 Met Office Hadley Centre, Exeter EX1 3PB, UK 4 College of Engineering, Mathematics and Physical Sciences, University of Exeter, Devon EX4 4QF, UK 5 Secretariat of Jiangxi Meteorological Society, Nanchang 330096, China 6 Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089, China (Received March 10, 2020; in final form June 4, 2020)
ABSTRACT Based on the empirical orthogonal function (EOF) analysis, the East Asia–Pacific (EAP) teleconnection is extracted as the leading mode of the subseasonal variability over East Asia in summer, with a meridional tripole structure and significant periods of 10–30 and 50–70 days. A two-dimensional phase–space diagram is established for the EAP index and its time tendency so as to monitor the real-time state of EAP events. Based on the phase composite analysis, the general circulation anomalies first occur over the high-latitude area of Europe centered near Novaya Zemlya at the beginning of EAP events. These general circulation anomalies then influence rainfall over Northeast China, North China, and the region south of the Yangtze River valley (YRV) as the phases of EAP event progress. The representation, predictability, and prediction skill of the EAP teleconnection are examined in the two fully coupled subseasonal prediction systems of the Beijing Climate Center (BCC) and UK Met Office (UKMO GloSea5). Both models are able to simulate the EAP meridional tripole over East Asia as the leading mode and its characteristics of evolution as well, except for the weaker precursors over Novaya Zemlya and an inconspicuous influence on precipitation over Northeast China. The actual prediction skill of the EAP teleconnection during May–September (MJJAS) is about 10 days in the BCC model and 15 days in the UKMO model based on correlation measures, but is higher when initialized from the EAP peak phases or when targeted on strong EAP scenarios. However, both of the ensemble prediction systems are under-dispersive and the predictable signals extend to 18 and 30 days in BCC and UKMO models based on signal-to-error metrics, indicating that there may be further scope for enhancing the capability of these models for the EAP teleconnection prediction and the associated impacts studies. Key words: East Asia–Pacific (EAP) teleconnection, subseasonal, phase–space diagram, pr
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