干旱区均匀裸土型陆气相互作用中几个关键问题的观测研究

Since the late 1980s, many surface layer observations have showed that the observed energy is not closed, and even more the residual energy is high evidently. This phenomenon is not satisfied the energy conservation, therefore once the fact is revealed, meteorologists immediately aroused extensive attention to this problem. The surface layer energy unclosure not only affectes land surface process models, but also has great impacts on weather forecast, climate prediction through the coupling of the land surface process models into weather and climate models. At the present stage, the research about boundary layer and land surface process has been baffled by the energy unclosure, the heterogeneity of underlying surface, and the uncertainty of surface soil heat flux. Even more, these three problems mix together make the study of boundary layer and land surface process more complicated, and also brought confusions into the surface layer observation research. This problem has seriously limited the development of the boundary layer and land surface processes. Facing the difficulties, this project would design a long-term observation with new concept over the homogeneous bare soil surface in an arid region to solve the problem related to the energy unclosure. This study sought to make clear the following key issues:.1) How does the energy unclosure develop? and what is the relationship between the energy closure ratio with the characteristics of the atmospheric turbulence?.2) How does the energy closure ratio in the surface layer affect the universial function based on the M-O similary? and how to the land surface process simulation?.3)Evaluating the precent calculation methods of the surface heat flux.

自20世纪80年代末，研究发现近地层观测的能量是不闭合的，甚至不闭合比较显著。这不符合能量守恒定律，故一经发现，立即引起气象学家的广泛关注。近地层观测的能量不闭合不仅影响着陆面过程模式，而且会通过陆面过程模式和天气、气候模式的耦合对天气数值预报、气候数值预测等研究产生重要影响。现阶段边界层和陆面过程的研究中呈现出"能量不闭合、下垫面非均匀性、地表热通量计算和土壤层观测的不确定性交织在一起使边界层和陆面过程的研究复杂化，也为边界层的观测研究带来困惑"。该问题严重制约着边界层和陆面过程的发展。面对困局，本项目将通过全新理念设计在干旱区均匀裸土下垫面上通过长期观测研究突围。该项研究力图澄清如下关键问题：1）近地层的能量不闭合是如何形成的？它与大气湍流运动特征有何种关系？2）能量不闭合对M-O相似性理论构建的普适函数有何种影响？对陆面过程数值模拟有什么影响？3）现有地表热通量计算方法的适用性？

研究发现近地层观测的能量是不闭合的，甚至不闭合比较显著。这不符合能量守恒定律，故一经发现，立即引起气象学家的广泛关注。近地层观测的能量不闭合不仅影响着陆面过程模式，而且会通过陆面过程模式和天气、气候模式的耦合对天气数值预报、气候数值预测等研究产生重要影响。现阶段边界层和陆面过程的研究中呈现出"能量不闭合、下垫面非均匀性、地表热通量计算和土壤层观测的不确定性交织在一起使边界层和陆面过程的研究复杂化，也为边界层的观测研究带来困惑"。该问题严重制约着边界层和陆面过程的发展。面对困局，本项目通过设计在干旱区均匀裸土下垫面上通过为期18个月的观测研究，研究明确了下面几个关键问题：比较研究了现有的6种地表热通量计算方法的性能；通过构建新的参数化方案，提高现有陆面过程模式的模拟性能；分析了中尺度大气运动对湍流特征的影响。