青藏高原复杂地形湍流结构及湍流强度参数化研究

The turbulent structure and turbulent parameterization under complex conditions is the hot issue in the boundary-layer meteorology, and also is one of the most difficult problems of the land-atmosphere interaction. The high altitude, low air density, abnormal buoyancy and the complex terrain have significant influence on the turbulent structure and its motion in the Qinghai-Tibet Plateau. Study on the characteristics of turbulent structure and turbulent parameterization over the complex terrain of Qinghai-Tibet Plateau not only has a great significance for the understanding of regional land-atmosphere interaction, but also is important to understand the interaction between atmospheric heat source of the plateau and adjacent regional climate system. This project intends to use the boundary layer observational data over complex terrain of Naqu region observed by Lanzhou Institute of Arid Meteorology, the 3rd Tibetan Plateau Atmospheric Scientific Experiment observational data, and the plateau boundary layer observational data of the intergovernmental cooperation in science and technology project of JICA (Japan International Cooperation Agency) program. The comprehensive application of Hilbert-Huang transform, Wavelet transform, digital filter and theoretical analysis to deeply study the multi-scale structure of turbulence caused by complex terrain, reveal the turbulence transport mechanism in the near surface layer of convective boundary, analyze the influence of mesoscale motion caused by topographic factor on regional turbulence transport during the stable stratification, establish turbulent intensity parameterization under considering the influence of complex topographic factor. The project will significantly deepen our understanding in the formation mechanism of special boundary structure over Qinghai-Tibet Plateau, and provided a theoretical basis for numerical model to precisely descript the turbulent transport mechanism under complex terrain.

复杂条件湍流结构及湍流参数化是边界层气象学领域的热点问题，也是陆—气相互作用研究面临的难点问题。青藏高原海拔高、空气密度小、浮力异常，高原复杂地形对湍流结构及湍流运动影响突出。开展青藏高原复杂地形湍流结构与湍流参数化研究，对理解区域陆—气相互作用过程、揭示高原大气热源与邻近区域气候系统间的互馈机制具有重要意义。本项目拟利用那曲地区复杂地形边界层观测资料、第三次青藏高原大气科学试验观测资料及JICA计划青藏高原边界层历史观测资料，综合运用希尔伯特-黄变换、小波分析、数字滤波和理论分析等方法，研究高原复杂地形引起的湍流多尺度结构特征，揭示复杂地形对流边界层的近地层湍流输送机制，分析稳定层结地形引起的中尺度运动对局地湍流输送的影响，建立考虑复杂地形影响的湍流强度参数化关系。该项目完成会对青藏高原大气边界层特殊结构的形成机制有新认识、会对数值模式中客观描述复杂地形湍流输送过程提供理论依据。

复杂条件湍流结构及湍流参数化是边界层气象学领域的热点问题，也是陆—气相互作用研究面临的难点问题。青藏高原海拔高、空气密度小、浮力异常，高原复杂地形对湍流结构及湍流运动影响突出。开展青藏高原复杂地形湍流结构与湍流参数化研究，对理解区域陆-气相互作用过程、揭示高原大气热源与邻近区域气候系统间的互馈机制具有重要意义。. 主要研究内容包括三个方面，即揭示青藏高原复杂地形对流边界层的湍流结构，研究青藏高原复杂地形稳定层结的湍流特征，建立青藏高原复杂地形湍流强度参数化关系。重要成果有：揭示了青藏高原复杂地形条件能量分配特征及影响因子，分析了青藏高原复杂地形对湍流强度的影响，发现了青藏高原复杂地形湍流多尺度结构，弄清了由非季风区向季风区过渡过程中大气边界层结构特征，并通过大涡模拟揭示了青藏高原深厚大气边界层的形成机制。通过开展青藏高原复杂地形大气边界层综合观测试验，获得了项目所需的高质量连续观测数据，并为后续开展高原复杂地形陆-气相互作用研究积累类了宝贵资料。. 通过建立复杂地形湍流强度参数化关系，检验了相似性理论在复杂地形条件下的适用性，该成果丰富了边界层气象学理论。大涡模拟揭示了高原深厚边界层形成机制，发现强感热通量、高大地形的动力抬升作用和上层动量下传是影响其发展的三大主要因素，成果为认识高原边界层形成机制、改善区域数值模式中边界层方案提供了理论依据。研究成果在中国气象局兰州干旱气象研究所区域数值模式中的初步应用表明，上述研究可有效改善现有模式对高原边坡降水的预报效果。