夏季低频东亚-太平洋遥相关型的特征、形成和维持机制及影响

During boreal summer, the East Asia-Pacific （EAP） pattern is one of the most well- known meridional teleconnection of the northern hemisphere. As revealed by many previous studies, the variation of EAP pattern is effected by SST anomalies in the tropical basins and the climatological mean fields of the East Asia monsoon region. Most of these previous studies mainly focus on either monthly or seasonally timescale, the excitation and evolution process of EAP wave train can not be obtained. Our pre-study showed that the EAP pattern also exhibit apparent low-frequency variations. Moreover, the low-frequency EAP pattern has distinct characteristics in the spatial distribution and the vertical structure compared to the monthly or seasonally mean EAP pattern, and mechanism of triggering and maintaining for the EAP teleconnection could also be different..This project aims to systematically investigate the characteristics of the special-temporal evolution of the low-frequency EAP teleconnection , reveal the key factors that responsible for the triggering and maintaining process of the low-frequency EAP pattern. The external factors that modulate the low-frequency EAP on interannual timescale would also be examined. Furthermore, this study also aims to investigate the impact of the low-frequency EAP pattern on the weather anomaly as well as the extreme weather events in East Asia during boreal summer to provide reference for improvement of extended-range weather forecast and reduction of the meteorological disasters.

东亚-太平洋（EAP）遥相关是北半球夏季最显著的遥相关型之一，其活动常常同东亚周边区域的大气环流及气候异常密切相关，而EAP遥相关本身变化受到热带海温异常和东亚区域背景环流场的影响。前人研究多基于月-季节平均，不能得到EAP波列的激发和演变过程。申请者预研究发现EAP波列具有显著的低频尺度特征，且其空间分布、垂直结构等特征同基于月-季节尺度研究得到的EAP存在明显差异，其触发、形成和维持机制也可能存在不同。本项目以低频EAP波列为研究主体，采用资料分析、热/动力学诊断和数值模拟相结合的研究方法，在揭示低频EAP波列时空演变特征以及波列的触发和维持机制的基础上，寻找影响低频EAP年际变化的外部因子，进一步探究低频EAP遥相关波列对北半球天气异常和极端天气事件的影响，为改善夏季中长期天气预报以及减轻气象灾害提供参考。

东亚-太平洋（EAP）遥相关是北半球夏季最显著的遥相关型之一，其活动常造成东亚周边 区域的大气环流及气候异常。然而，夏季低频 EAP 遥相关的结构特征、演变过程、触发和维持机制及其对东亚天气异常的影响，以及年际变化因子等问题目前尚不清楚。本项目以夏季低频东亚-太平洋遥相关型的特征、形成和维持机制及影响为研究对象，通过观测资料诊断和动力学分析，揭示了季节内尺度EAP遥相关型在三维结构上呈“环太平洋沿大圆路径的正斜压耦合结构”、波列异常中心沿大圆路径分布和波能量由热带地区沿大圆路径单向频散等特征；发现菲律宾以东海域的准双周对流活动是触发准双周EAP遥相关型的关键因子，位于上游欧亚大陆上空的准双周环球遥相关（CGT）在太平洋中纬度地区产生准正压扰动和中纬度太平洋地区高频与低频瞬变涡旋的正压强迫，对准双周EAP遥相关型的中下游异常信号维持和加强有重要作用；揭示了热带关键海区对流活动、夏季赤道太平洋地区海温异常型和上游准双周CGT活动变化是夏季低频EAP波列年际变化的影响因子；阐明了夏季低频EAP遥相关 波列对与我国夏季季节内降水的联系及其影响机制。在项目资助下，共完成发表项目标注论文24篇，其中国际SCI论文22篇，国内核心期刊论文2篇。18篇SCI论文发表于JC, CD, GPL, JGR等4种国际主流学术期刊。在项目资助下培养研究生6人，其中博士生2名，硕士生4名。已经获得博士学位的2名，获得硕士学位的4名。