青藏高原和东亚地表位涡制造对我国东部强降水天气过程的影响

Intense precipitation occurs due to the abnormal development of energy and water cycle in the atmosphere, and has serious impacts on social development. About two thirds of the energy that drives the atmospheric motion comes from the underlying earth's surface, and about 85% of the atmospheric water vapor is confined in a thin layer of 3 kilometers above the earth's surface. The exchanges of energy, momentum and water vapor near the earth's surface are essential physical processes for maintaining the weather processes. Actually, many geophysical fluid dynamic issues can be described by the potential vorticity (PV) dynamics. This is because the PV change is an equation of the divergence of PV flux, the gross PV generation on an isentropic surface is determined by the linear integral along its closed boundary of the component of the PV flux that is perpendicular to the boundary and inward pointed. This implies the external PV flux distribution at the earth's surface has significant direct impacts on the internal general circulation of the atmosphere. The Tibetan Plateau itself is an important PV source of the atmosphere, the influence on the surrounding weather development of the surface PV generation on the Tibetan Plateau and the surrounding area should play significant roles as well. The recent advances of the PV dynamics in treating the surface boundary PV forcing provides new methods for investigating the linkage between the external surface PV generation and the internal PV development and atmospheric circulation. Grasping these encouraging progresses in PV dynamics and based on the accomplishment in the study of torrential rain development in China, this proposal will focus on analyzing the PV generation processes along the intersection boundary between isentropic surfaces and the earth's surface over the Tibetan Plateau and East Asia, and their influence on the regional and persistent intense precipitation associated with the development of the wet phase of the atmospheric intra-seasonal oscillations. The understanding will provide theoretical background for improving short-term and mid- term weather forecasts.

强降水过程是大气能量和水分循环异常发展的表现，对社会发展和日常生活有重大影响。驱动大气运动的能源约三分之二来自下垫面，约85％的大气水汽集中在近地表三公里以下，发生在海陆气边界面的能量和水分交换是维持长中短期天气的基本过程，受地表位涡制造直接影响。青藏高原也是大气重要的位涡源区，青藏高原和东亚地表位涡制造对我国东部强降水天气当有重要影响。许多地球流体问题都可以用位涡（PV）动力学描述；近期PV动力学的边界研究新突破为探讨地表过程对天气气候的影响提供了新思路。本申请项目将基于我国天气研究的成果，利用PV动力学边界研究的新进展，研究局地边界位涡的制造对区域大气环流、水汽输送和上升运动发展的贡献；分析等熵面与青藏高原和东亚地表相交的交界处的位涡制造；揭示其对发生在我国东部的、与季节内振荡湿位相的发展有关的、区域性和持续性的大、暴雨和中大雪等强降水天气过程的影响，为提高天气预报准确率提供理论依据。

持续性的异常强降水是造成我国东部经济损失的主要气象灾害。强降水过程的发展不仅取决于大气环流的内部变率，还取决于海陆气边界面上的能量、动量和水分交换。诱发大气环流异常的涡动的位涡源位于地表。本研究聚焦于大气等熵面与青藏高原和东亚地表的交界处的位涡制造；揭示其对我国东部区域性和持续性的大暴雨和中大雪等强降水过程的影响。. 项目组经过五年努力，圆满完成计划的任务和目标；取得一系列研究成果。其中若干成果是创新性和原创性的，可概括为如下三个亮点创新成果：. 1.构建先进的位涡源汇可视化计算模块；建立位涡环流（PVC）的原创性理论。通过广义坐标变换建立位涡源汇诊断模块，直接耦合在FGOALS-f2气候系统模式中，建立地表位涡演变和预报的展示平台，为极端天气的短、中期动力预报提供新思路！建立的PVC理论证明热带的位涡强迫源通过激发半球内部PVC和青藏高原作用从而导致中高纬度气候异常,为“热带-热带外”相互作用的研究提供新视角。. 2.建立位涡重构理论，导出位涡框架下包括加热的新的垂直运动方程，揭示激烈天气形成机制。证明当位涡守恒时，大气垂直涡度也可通过构成位涡变量的变化而激烈发展；青藏高原上的位涡重构导致位涡和垂直涡度强烈发展从而影响下游的天气气候。首次导得有加热的地转（Ertel）位涡理论和垂直运动联系的方程，证明位涡平流的垂直差异和垂直运动三个分量之间的互反馈是驱动气旋生消的重要因子。部分成果应邀作为专题文章（FEATURE ARTICLE）发表在JGR-Atm.为庆祝AGU成立一百周年出版的“Grand Challenges Centennial Collection（大挑战世纪文集）”特刊上。. 3.揭示位涡源汇时空变异影响区域极端气候异常的新机制。建立比传统的地表感热指数更优秀的“青藏高原表层位涡指数”，它能够很好的表征青藏高原抬升加热对大气的综合影响，具有很好的应用前景！证明夏季青藏高原表面PV与东亚降水和高层环流在年际变率显著相关。揭示青藏高原近地表非绝热加热垂直梯度的日变化对高原涡形成和东移的影响及其天气效应。. 此外，项目还开展成果科普介绍。