论地表能量不平衡的原因及其解决办法  

Causes of Surface Energy Imbalance and Its Possible Solutions

作　　者：李宏宇[1,2] 张强[1,2] 赵建华[1,2] 

机构地区：[1]中国气象局兰州干旱气象研究所,甘肃省干旱气候变化与减灾重点实验室,中国气象局干旱气候变化与减灾重点开放实验室,甘肃兰州730020 [2]兰州大学大气科学学院半干旱气候变化教育部重点实验室,甘肃兰州730000

出　　处：《干旱区研究》2012年第2期222-232,共11页Arid Zone Research

基　　金：国家自然科学基金重点项目“黄土高原陆面过程观测与试验研究”(40830957)

摘　　要：地表能量不平衡问题一直是困扰地-气相互作用的难点之一。总结国际和国内一些观测试验不同下垫面的能量平衡状况,介绍了表征地表能量平衡状况的常用统计方法,并对能量不平衡的不同因素进行了探讨。浅层土壤热储存,由气温变化、光合作用和植被热储存等引起的地上热储存,以及垂直平流都会影响地表能量平衡。此外,由于不同能量分量足迹的差异,不均匀下垫面会影响通量观测的代表性和准确性,而且还会诱发中尺度环流和大尺度涡旋等复杂大气运动,不平稳的大气状态和夜间非充分混合的湍流,同样会困扰湍流通量的观测。为此,在对湍流通量严格质量控制的基础上,从单点涡动相关(简称EC)系统的平流热通量修正、多点EC的通量空间平均和大孔径闪烁仪(简称LAS)等通量足迹较大的通量修正等方面,对能量不平衡问题提出解决办法。建议在湍流混合不充分时,利用Penman-Monteith公式计算地表潜热;并对EC水汽通量与蒸渗计观测的真实地表蒸散进行了简单讨论,提出了大型蒸渗计算地表潜热通量的可能试验方法。Surface energy imbalance is a difficulty in the study on land surface interaction.A series of experiments related to surface energy imbalance have been conducted in different climate zones and underlying surfaces in the world.Over the past two decades,some systematic progresses on this issue have been made.This paper summarizes the research achievements of surface energy balance in land surface process experiments conducted over different underlying surfaces,introduces the statistical methods to characterize surface energy imbalance,and discusses the possible causes resulting in energy imbalance.Heat storage in upper soil layer and energy storage due to plant photosynthesis and temperature variation of canopy and air has an effect on surface energy balance.Vertical sensible advection is also discussed as a cause resulting in surface energy imbalance.Because of footprint differences of energy components,heterogeneous surface has an impact on representation of measurements,and it also induces local circulations and large-scale eddy.Together with the nighttime inadequate turbulent mixing,the inconsistent atmospheric status makes some troubles to the flux measurements.After data quality control is processed strictly,three schemes are put forward to solve the energy imbalance,heat flux advection correction for single-point EC system,spatial averaging of flux observations for multi-point one and the replacement of EC system by LAS with larger measurement footprint.It is suggested that the nighttime EC latent heat flux be substituted by the Penman-Monteith modeled flux in cases of insufficient turbulent mixing.A simple discussion is made by a comparison between the EC water vapor flux and the actual surface evaporation observed by the weighing evaporation instrument and the weighing evaporation instrument as a possible test method,and it is proposed to calculate surface latent heat flux.

关 键 词：地表 能量平衡 地-气系统 下垫面 环流 热通量 

分 类 号：P339[天文地球—水文科学]