青藏高原调控区域能量过程和全球气候的机理

The giant mountains in Asia play an essential role in the formation and variation of Asian monsoons. How the Tibetan Plateau (TP) regulates the regional energetic processes and global climate is a key scientific issue of the regional and global "Water, Energy and Climate" program. A thorough understanding of the mechanisms behind can advance climate prediction substantially. This project will explore the atmospheric adaptation and climatic effects to the uplifted heating from the high topography of the Iranian and Tibetan Plateaus under conditions of zonal flows with different strength and of baroclinicity during different seasons. We will adopt and develop the theories of potential vorticity and of equivalent topography height, carry out multi-source data analysis and numerical simulation by using regional and global climate models to investigate the interactions of the Plateaus with Asian monsoons. Specifically we will consider the two plateaus and the water vapor transportation induced by the pumping and suction effects of the plateaus as an integrated system – the Iranian-Tibetan Plateau system (TIPs). We will analyze the characteristics of atmosphere-land coupling over the TIPs surface and the feedback between the coupling and the atmospheric diabatic heating, focusing on the formation of the thermal structure above the TP and its climatic impacts. Thereby we will develop the thermal adaptation theory in explaining the atmospheric circulation responding to the uplifted and non-uniform plateau diabatic heating; we will clarify the regulation of the Tibetan Plateau on the thermal conditions of the TIPs and the energetic processes in the surrounding region, and we will disclose the mechanisms of the TIPs affecting the coupling between the circulation in the upper and lower troposphere in the Asian monsoon region, monsoonal onsets and development. The results will quantify the physical and dynamical processes whereby the TIPs interacts with the Asian and global climates.

亚洲大地形在亚洲季风形成和变异中起着重要作用。深入理解青藏高原调控区域能量过程和全球气候的机理有助于提高气候预测水平，是研究区域和全球“水、能量与气候”的一个核心科学问题。本项目拟采用位涡和等效地形高度理论、多源资料分析、区域和全球气候系统模式数值模拟相结合的方案，研究大气对大地形抬升的加热的热力适应过程；研究不同季节大气基本气流和斜压性背景下伊朗高原和青藏高原加热的气候效应；并将两大高原及其相关的水汽输送/抽吸作为一个系统－青藏高原-伊朗高原热力系统（TIPs），分析两大高原地气耦合特征以及和大气热源之间的反馈，重点探讨青藏高原热力结构形成的原因及其气候效应。由此发展大气环流对高原抬升加热和TIPs非均匀热力强迫的热力适应理论，阐明青藏高原对TIPs热状况及周边区域能量过程的调控作用，TIPs影响亚洲季风区高低空环流耦合、季风爆发和推进的机制，揭示青藏高原影响亚洲区域和全球气候的机理。

系统开展了青藏高原调控区域能量过程及其影响机理的研究，在如下4个方面取得显著进展。（1）提出TIPS概念。揭示了伊朗-青藏高原表面热通量的季节，年际和年代际多时间尺度变化特征；揭示了夏季青藏高原和伊朗高原感热加热存在相互影响和反馈, 形成了观测到的伊朗高原感热加热-青藏高原感热加热和凝结潜热释放-大气垂直环流之间的准平衡耦合系统(TIPs)。该系统与欧亚大陆大尺度热力强迫共同作用, 形成了对流层上层的暖性但在平流层下层为冷性的强大的反气旋环流南亚高压, 从而影响区域和全球的天气气候；发现了青藏高原上独特的云的宏观和微观垂直结构、降水和云辐射效应。（2）揭示TIPs影响印度洋海气相互作用、亚洲季风和北半球定长波的过程与机理。从天文和水文的角度理解TIPs对亚洲水汽输送和夏季风形成的影响，修正经典的Gill模型，阐明对流层上层南亚高压和暖中心的形成和变化机理；明确了印度洋海气相互作用对青藏高原热力强迫的调控作用。TIP热力强迫导致与印度洋上出现与印度洋偶极子分布相似的海温变化，该高原热力强迫造成的海气相互作用异常却是要减弱地形对亚洲季风的直接强迫作用。（3）揭示TIPs系统影响亚洲季风年际变化及极端灾害事件的过程与机理。在年际和季节尺度的变化上，证明南亚高原强度异常表现为其西、东部的位势高度(温度)异常，与高原东部到长江中下游一带的季风潜热释放的异常关系密切；发现从春到初夏，春夏季TIP地表热通量存在相互联系及对初夏南亚高压和亚洲季风的影响。而在冬季青藏高原地表位涡密度强迫东移激发了我国南方的冰雪灾害，揭示出青藏高原位涡密度强迫激发中国东部激烈天气发生的一种新机制。（4）改进区域和全球气候系统模式。改进模式陆面参数化方案，云中水凝物抗相关厚度参数化方案和次网格云量参数化方案，阐明CMIP5模式表面温度冷偏差的原因和其中物理过程。研究成果丰富了青藏高原气候动力学的研究，对于提高气候预测水平具有十分重要的科学意义和参考价值。