涡动相关能量闭合问题的研究进展

Progress in the Energy Closure of Eddy Covariance Systems

涡动相关系统(EC)观测的湍流通量总是低于有效能量(净辐射与地表热储量之差),两者的差值可达有效能量的10%～30%。这种EC观测的湍流通量低估的现象,称之为"EC能量闭合问题",已成为微气象学研究中的一大瓶颈。过去的几十年间大量学者对此问题进行了深入研究,积累了丰富的认知。系统介绍了EC能量闭合问题的成因,总结了学者对于EC能量闭合问题的认识以及基于这些认识提出的可能的修正方案,并详细评述了这些修正方案的优劣。与之前的综述不同,重点介绍了基于大涡模拟(LES)研究EC能量闭合问题的方法和进展。指出目前缺少高精度且时间连续、空间密集(如矩阵式观测)的地表通量观测数据集、LES尚不足以完全表征真实的EC观测、大尺度湍涡影响EC能量闭合的机制尚不清楚等问题。今后应加强大尺度湍涡影响EC能量闭合的机制研究,同时开展空间矩阵式观测,验证LES的结果。

The sum of turbulent fluxes measured by the eddy-covariance method is often 10%～30% lower than available energy（ i. e.,the net radiation minus the ground heat flux）. This systematic bias in the EC method is called the ＂ EC energy closure problem＂ and has been one of the biggest challenges in micrometeorology. In the past decades,lots of studies have focused on this problem and have found extensive knowledge about it. In this paper,we introduced the reasons to the EC energy closure problem and systematically summarized the understandings on this problem with a discussion regarding the merits and limitations of possible correction methods. Compared with previous overview studies,our study focused on the methods and progresses on the EC energy closure problem using the Large Eddy Simulation（ LES）. The existing problem,e. g.,the lack of high quality and high spatial density of ＂ surface true fluxes＂ observations（ e. g.,matric observations）,the failure of fully emulating the EC using the LES and how to mechanistically understand that large eddies affect turbulence structures and lead to nonclosure problem,hinder the further understanding of the EC energy closure problem. Thus,in the future,focus should be put on the mechanistic understanding of how large eddies affect the non-closure problem and some dense field observations to obtain the high quality ＂ surface true fluxes＂.