中文摘要：

利用中国站点观测降水资料、国家气候中心第2代月动力延伸预报模式（BCC_DERF2.0）的回报和预报数据、NCEP/NACR再分析资料和国家气候中心实时发布的月尺度降水预测评分数据,通过评估和诊断分析发现,在2015/2016年超强El Nino事件背景下,这两年内业务发布的月降水预报能力有明显不同,BCC_DERF2.0对月环流的预测技巧也存在差异：在2015年（El Nino发展位相）,降水预报和环流预测技巧较高且稳定,而在2016年（El Nino衰减位相）的预报技巧总体偏低。进一步的研究显示,亚洲—太平洋涛动（Asia-Pacific Oscillation,APO）可能是导致2015年和2016年夏季预测技巧高低的重要影响因素。2015（2016）年夏季为APO低（高）指数年,且2016年具有高指数年的典型环流特征。而APO高指数对应的环流特征与El Nino衰减位相对西北太平洋环流的影响不同,在El Nino和APO的物理影响途径不一致时,将直接影响东亚环流可预报性的高低及动力气候模式的预报技巧,即El Nino在发展和衰减位相与APO型不同组合的影响是2015和2016年月预测技巧有差异的重要原因。

英文摘要：

The ENSO cycle is a strong signal in atmosphere-ocean interaction,and plays a significant role in the global climate,including the East Asia monsoon region. Typically,in the developing phase of El Nino,the convection is strong in the east-central tropical Pacific,and weak in the west tropical Pacific and Maritime continent. In the following summer,the northwest subtropical high is weaker than normal,and is located southward from its normal position. As a result,the southwest jet stream from the Bay of Bengal is weaker than normal,and carries less moisture to mainland China. In the decaying phase of El Nino,the Philippines anti-cyclone can persist until sum-mer,and the northwest subtropical high is strong and located westward from its normal position. The southwest jet stream from the Bay of Bengal is much stronger than normal and carries more moisture to mainland China. In addition,the Yangtze River typically experiences flood events. Aside from the ENSO cycle,the vertical averaged eddy temperature difference between the Asian and Pacific may have less influence on the East Asia summer monsoon. The Asian-Pacific Oscillation（ APO） and its associated indexes can be used to identify this difference. With higher APO index years,in the upper troposphere the summer South Asian high and North Pacific trough are stronger,while the westerly jet stream over Asia and easterly jet stream over South Asia are strengthened. Further more,in the lower troposphere the Asian lowand North Pacific subtropical high are stronger. The anomalous westerly prevails over South Asia,and the Meiyu front is located northward from its normal position. Such a circulation pattern may lead to greater rainfall in northern China,southern China and South Asia. Further analysis shows that the combined impact of the ENSO phase and APO index has different predictability for the East Asia climate. This paper will study the 2015/2016 monthly prediction skill differences under the background of super strong El Nino events and different APO index condit