黄土高原冬季湍流相干结构在地表能量平衡中的作用  

The role of turbulent coherent structure on surface energy balance on Loess Plateau in Winter

作　　者：赵建华[1] 张良[1] 王胜[1] 梁芸 隆霄[3] 王涓力 ZHAO JianHua;ZHANG Liang;WANG Sheng;LIANG Yun;LONG Xiao;WANG JuanLi(Key Laboratory of Arid Climatic Changing and Reducing Disaster of Gansu Province(Chinese Meteorological Administration),Lanzhou Institute of Arid Meteorology of Chinese Meteorological Administration,Lanzhou730020,China;Lanzhou Regional Climate Center,Lanzhou730020,China;College of Atmospheric Science,Lanzhou University,Lanzhou730000,China)

机构地区：[1]甘肃省(中国气象局)干旱气候变化与减灾重点实验室,中国气象局兰州干旱气象研究所,兰州730020 [2]兰州区域气候中心,兰州730020 [3]兰州大学大气科学学院,兰州730000

出　　处：《地球物理学报》2023年第6期2292-2305,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金(重点)项目(41875020,42230611,41875022,41630426,41375019);中国气象局创新发展专项(CXFZ2022J049);甘肃省自然科学基金(20JR10RA446);甘肃省气象局第八批“十人计划”项目资助。

摘　　要：地表能量不平衡问题是近40年一直困扰微气象学界的重要难题.本文利用黄土高原定西干旱气象与生态环境试验站的相关数据,通过将湍流分解为相干结构部分和非相干结构部分,在涡动相关法中引入相干结构(Coherent structure,简称为CS)的贡献,探讨了CS在地表能量平衡中的作用.研究发现:(1)CS出现频次高,间歇性显著,在30 min平均时间中出现的数目为38个,出现时间与未出现时间分别占40%和60%左右;(2)CS对通量影响显著,引入CS贡献后,白天垂直动量通量、感热、潜热和湍流通量(感热与潜热之和)等4个通量计算的准确性均获得显著提高,分别提高达26%(0.01 m^(2)·s^(-2))、24%(25.33 W·m^(-2))、31%(6.23 W·m^(-2))和30%(31.66 W·m^(-2)).而不考虑CS的传统方法对这4个通量低估达19%、22%、21%和23%;(3)CS对4个通量的贡献分别为36%、41%、33%和50%;(4)传统方法得到的地表能量平衡闭合率EBR只有0.76、能量平衡残差Res为41.9 W·m^(-2),远未平衡.考虑CS贡献后,EBR增大至0.96、Res降低至10.4 W·m^(-2),地表能量接近闭合;(5)EBR与Res少量的未闭合部分可以非均匀地表产生的垂直感热平流解释.结果表明,CS大幅提高了地表能量的闭合水平,它是实现地表能量平衡的关键因素之一,是产生地表能量不平衡的最重要原因之一,应该在涡动相关法中考虑CS的贡献.Surface energy imbalance is a common problem in micro meteorology in recent 40 years.Based on the data from the Experimental Station of Arid Meteorology and Ecological Environment in Dingxi,Loess Plateau,this paper discusses the role of coherent structure(hereafter CS)in the surface energy balance by decomposing turbulence into coherent and incoherent parts and introducing the contribution of coherent structure into the eddy covariance technique.The results show that:(1)CS has a high occurrence frequency and a strong intermittence.The number of CS appearing in 30min average time is 38,and the occurrence time and non-occurrence time account for about 40%and 60%,respectively;(2)CS has an significant effect on fluxes at daytime.With consideration of CS′s contribution,the accuracy of vertical momentum flux,sensible heat,latent heat and turbulent flux(the sum of sensible heat and latent heat)is significantly improved by 26%(0.01 m^(2)·s^(-2)),24%(25.33 W·m^(-2)),31%(6.23 W·m^(-2))and 30%(31.66 W·m^(-2)),respectively while the traditional method without considering CS underestimates the four fluxes by 19%,22%,21%and 23%.(3)The contributions of CS to the four fluxes are 36%,41%,33%and 50%,respectively;(4)EBR,the surface energy balance ratio,obtained by the traditional approach without considering CS is only 0.76,and Res,the surface energy balance residual,is 41.9 W·m^(-2),which is far from balance.However,after CS′s contribution is introduced,the EBR increases to 0.96,and Res decreases to 10.4 W·m^(-2),which is close to closure of surface energy;(5)The small number of unclosed parts of EBR and Res can be explained by vertical sensible heat advection caused by heterogeneous surface.The results show that CS greatly improves the closure level of surface energy,which is one of the key factors to realize the surface energy balance and one of the most important reasons for the surface energy imbalance.Consequently,the contribution of CS should be introduced into the eddy covariance technique.

关 键 词：地表能量不平衡 相干结构 涡动相关法 

分 类 号：P425[天文地球—大气科学及气象学]