亚洲-太平洋涛动的前兆信号与中国东部夏季旱涝短期气候预测

The short-term climate prediction for droughts and floods in eastern China is a scientific focus and also very difficult. In current research and operational forecast, many atmospheric circulation systems or atmospheric oscillation associated with droughts and floods in eastern China have been taken into account. However, these atmospheric circulation anomalies are mainly related to anomalous sea surface temperature or sea ice forcing. To some extent, the contributions of the land-surface boundary conditions and land-air interactions are ignored. The Asia-Pacific Oscillation (APO) reflects the land-sea thermal contrast over Asian-Pacific region, contains comprehensive information of sea-land-atmosphere interactions, and integrates several anomalous atmospheric circulation patterns. Moreover, the APO has close physical relationships with the East Asian summer monsoon and its corresponding precipitation anomaly over eastern China and thus might be considered as a new indicator suitable for the forecast of summer droughts and floods in eastern China. Therefore, in the present project, using statistical analyses and numerical simulation methods, the relationships between a variety of precursory signals (including East Asian continental land-surface conditions, sea surface temperature anomalies at Asian adjacent oceans and large-scale atmospheric circulations) and the summer APO would be investigated, and the physical linking processes of precursory signals affecting the summer APO would be mainly studied. On the basis of the above physical mechanism research, a conceptual prediction model for the summer APO would be established. Eventually, the present project is expected to provide a new idea and a method for the short-term climate prediction for summer droughts and floods in eastern China.

适用于中国东部旱涝的短期气候预测理论与方法是科学研究的重点和难点。目前的研究和预测业务中已考虑了多个影响中国东部旱涝的大气环流系统或大气涛动，但现有的这些大气环流异常型主要与海温、海冰等外强迫作用相联系，在一定程度忽视了陆面边界条件和陆气相互作用的贡献。亚洲-太平洋涛动（Asian-Pacific Oscillation，APO）反映了海陆热力差异，包含了海-陆-气相互作用的综合信息，并整合了现有的多种环流系统或大气涛动，且与东亚夏季风及其相应的降水分布具有密切的物理联系，是适用于中国东部夏季旱涝预测的新指标。因此，本项目拟从APO入手，综合统计分析和数值模拟的方法，考察包括东亚大陆陆面状况、周边海域海温异常和大尺度环流等在内的各种前期信号与夏季APO的关系，重点探讨前期信号对夏季APO影响的物理链接过程，进而建立APO的预测模型，以期为中国东部夏季旱涝的短期气候预测提供新的思路和方法。

目前的研究和预测业务中已考虑了多个影响中国东部旱涝的大气环流系统或大气涛动及其相应的海温异常强迫，但现在一定程度忽视了陆面边界条件和海-陆-气相互作用的协同贡献。亚洲-太平洋涛动（Asian-Pacific Oscillation，APO）反映了海陆热力差异，包含了海-陆-气相互作用的综合信息，是适用于中国东部夏季旱涝预测的新指标。因此，本项目从APO入手，考察各种因子对夏季APO影响的物理链接过程，从而为中国东部夏季旱涝的短期气候预测提供新的思路。..根据本项目的研究内容，得到的主要成果如下：..1）发现了青藏高原加热可通过调整高原与太平洋之间的垂直环流，进而影响夏季APO的年际变化。增强的青藏高原加热可以引起其上空对流层大气温度升高，同时也造成了青藏高原上空较强的上升运动。这一上升气流东传至太平洋地区开始下沉，通过对太平洋地区凝结潜热和绝热加热的调整作用，导致对流层中上层的偏冷，进而与青藏高原上空的偏暖一起构成了APO的异常。该工作指出了青藏高原热力异常通过对APO的调节作用进而影响我国乃至全球气候的新途径。..2）给出了前期热带中东太平洋海温异常通过青藏高原陆-气相互作用影响夏季APO的.物理链接过程。前期冬季中东太平洋海温异常持续到春季，通过“大气桥”效应引起春季北印度洋地区海平面气压异常。后者通过调控阿拉伯海和青藏高原之间的经向垂直环流，进而引起青藏高原西部的垂直运动异常和当地的春季降水，并将降水异常信号通过土壤湿度的持续性维持至夏季，引起青藏高原加热异常，最终影响了夏季APO。这一工作指出了青藏高原地区下垫面异常在传递前期热带太平洋海温异常信号中的重要作用。..3）基于APO与青藏高原加热以及不同海域海温异常的联系，给出前期春、夏季青藏高原积雪对我国东部梅雨期降水的影响过程；同时，也揭示前冬热带大西洋热力异常与印度洋热力异常协同影响我国南方地区夏季高温干旱的详细物理过程，并据此定义了前冬热带大西洋-印度洋热状况协同变化指数，为预测夏季我国南方地区高温提供了参考。