黄土高原半干旱区复杂地形条件下稳定边界层湍流特征研究

Accurate determination of turbulence in the boundary layer is one of the basic frameworks in the fields of land-atmosphere interactions, climate change, and environment assessment, et al. It is rather mature under unstable stratification in understanding the turbulence, while the research in a stable boundary layer is more difficult and unpredictable, restricted by the lack of reliable theoretical and observation. To further study of turubulence in a stable boundary layer over complex terrain, high quality observation data is needed. With this consideration, this project will execute field experiments at representative sites on the complex terrain in the semiarid region of the Loess Plateau, using eddy covariance system (EC), boundary layer meteorological measurements system, and large aperture scintillometer. Then the project will try to establish the processing methods to compute turbulent fluxes with EC data in stable boundary layer over complex terrain; assess the uncertainties in fluxes of momentum, sensible heat, latent heat and carbon dioxide; analyses the contributions of movements with various scales to the overall flux; investigate the characteristics of turbulence under various types of background flow fields; examine the validity of the Monin-Obukhov similarity theory (MOST) in stable boundary layer over complex terrain, and improve the turbulence parameterization scheme. This project surely has important scientific senses on the researches of regional land-atmosphere interactions and its response to the climate change, on understanding turbulence mechanism in stable boundary layer over complex terrain, and on improving the parameterization schemes of the atmospheric boundary layer in numerical models.

正确认识大气边界层湍流特征是陆气相互作用、气候变化、环境评估等研究与应用的重要基础。目前对不稳定边界层湍流的认识较成熟，而受理论基础和观测条件制约，稳定边界层湍流研究不足。欲深入研究稳定边界层湍流，需进行高精度有代表性的观测。本项目拟采用涡动相关系统、气象要素梯度观测、大孔径闪烁仪等多种先进观测仪器，在黄土高原半干旱区复杂地形典型站点，开展大气湍流观测；改进稳定边界层湍流资料的处理方法，评估动量、感热、潜热和二氧化碳通量观测的不确定性；研究不同尺度大气运动对通量输送的贡献；分析不同背景流场时湍流特征，讨论相似理论在复杂地形稳定边界层的适用性，改进该区域稳定边界层湍流参数化方案。为研究区域陆气相互作用及其对气候变化的响应、检验卫星遥感反演提供数据支撑；增进对复杂地形稳定边界层湍流机理的认识，提高大气数值模式的模拟能力，具有重要的科学意义。

为认识黄土高原半干旱区复杂地形上稳定边界层湍流特征，项目通过开展长期定点连续湍流观测和大气边界层垂直结构的加强期观测，获得了该区域复杂地形上稳定边界层结构和湍流特征的高精度观测资料。对比多种方法，建立和完善了适用于黄土高原复杂地形条件下稳定边界层湍流资料的处理方法，通过湍流尺度分解等多种分析手段，为研究黄土高原半干旱区陆-气相互作用提供了高精度有代表性的动量、感热、潜热和 CO2通量序列。系统研究了黄土高原复杂地形上稳定边界层湍流结构特征，获得了湍流特征参数，分析了边界层结构和典型背景流场时湍流特征；揭示了该地区地表能量分配机制、地表能量闭合特征；对比分析了半干旱区不同下垫面上陆-气相互作用特征。为改进大气边界层湍流参数化方案提供了理论支撑，为检验校准卫星遥感反演提供了数据基础。. 依托本项目，共完成论文15篇，其中发表SCI（E）论文7篇，发表中文核心论文7篇，投稿中论文1篇；培养博士研究生6名，硕士研究生6名。项目参与兰州大学“环境与气候灾害集成探测技术与应用”并获甘肃省科技进步一等奖（2018），项目主持人排名：2/12（证书尚未发放）。