【作者】 郑宁；

【导师】 张劲松；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2013， 博士

【摘要】 水热交换是地气间相互作用最为直接和显著的物理过程，一直是气象学、气候学、水文学、生态学等相关学科共同关注的重点和难点研究内容。显热通量（Sensible HeatFlux）是地表湍流运动和能量交换的驱动因子，准确测算区域显热通量显得尤为重要。但迄今为止，在植被分布非均一和地形起伏的复杂下垫面条件下，即便是公里尺度的通量观测技术及数据代表性的研究工作仍有许多问题需要解决。大孔径闪烁仪法（LargeAperture Scintillometers Methods）在公里尺度水热通量的测算研究中，具有广阔的应用前景。但目前大孔径闪烁仪法只能直接观测到大气折射指数的结构参数（the StructureParameter of the Refractive Index of Air，C_n²），测算显热通量需要进一步计算温度结构参数（the Structure Parameter of Temperature，C_T²），并根据大气湍流相似理论（Monin-Obukhov Similarity Theory，MOST），建立C_T²的MOST普适函数结合，气象数据才能得到最终结果。由于MOST要求地表相对平坦均一，该方法应用于山地森林等复杂或非均一植被显热通量的测算时，应当首先研究实际观测区域湍流运动特征，但至今为止，尚无详尽的研究文献报道。本研究以华北南部低丘山地栓皮栎-侧柏-刺槐混交林为研究对象，在研究实际观测区域湍流运动特征的基础上，判别湍流关键参数是否适合MOST适用条件，再建立适合于实际观测区域的温度结构参数的普适函数，并进行验证，旨在为该方法有效测算山地森林生态系统水热通量提供理论依据，以期促进公里尺度水热通量研究的发展，最终为深入研究了解森林生态系统在能量平衡和调节气候变化中的作用提供工作基础。主要结果如下：（1）湍流强度和风速的相关性很强。当U<3m/s时，湍流强度最大，并随着风速的增大明显减小。一年生长季中两个典型时段（2011年3月15日至4月15日，叶片萌芽生长期；2011年7月15日至8月15日，叶片生长完全期）的平均湍流强度分别为I_u=0.326，I_v=0.306， I_w=0.189和I_u=0.324， I_v=0.296， I_w=0.173。（2）各主要气象要素在山地人工林生态系统复杂下垫面条件下基本满足MOST适用条件。无因次风速方差在不稳定和稳定条件下均符合1/3次幂相似规律，垂直方向比水平方向上的拟合效果好，近中性层结下由σ_u/u_*=A, σ_v/u_*=B, σ_w/u_*=C式计算得到A、B和C的平均值在春季观测期为2.55、2.06和1.30，在夏季观测期为2.61、2.45和1.21，以上观测结果均与类似经典的陆面实验结果接近；同时无量纲湍流动能（Turbulent KineticEnergy,TKE）在不稳定和稳定条件下均符合1/3次幂相似规律；无因次温度方差在春季观测时期不同稳定度条件下均符合2/3次幂相似规律，在夏季观测时期不同稳定度条件下分别符合2/3次和1/3次幂相似规律。湍流谱结构基本符合-5/3规律，实际观测区森林冠层上方大气湍流是非各向同性的。（3）本研究建立的适合本研究区域实际条件的温度结构参数的普适函数准确性较高。研究MOST适用性发现，当热力因子较小时，大气处于非稳定状态，实测值离散程度最大；当热力作用较大时，大气处于稳定状态，离散程度小，说明了近中性条件下机械湍流对LAS观测中的MOST适用性有一定影响，而在对流不稳定时影响较小或可忽略。热力湍流越强，MOST适用性越好，反之则越差。湍流结构的实际情况可作为MOST适用性的判断方法，计算得到的普适函数为，f_TJiYuan=4.91（16.51ζ）^2/3_z/L <0；f_TJiYuan=6.43(1+2.20ζ^2/3)z/L>0；LAS实际观测与湍流谱方法计算得到的温度结构参数的一致性较好，大部分情况下相关系数都达到了0.9以上。（4）大气层结稳定时更要注意观测信息的空间代表性分析；在风向近似垂直于光径路线时，LAS观测得到的通量信息最全面完整。在大气层结稳定条件下，因湍流活动较弱，观测数据的源区面积相对较大；非稳定层结时，湍流活动旺盛，源区面积较小。大气层结稳定时最小的通量源区面积比不稳定时最大的源区面积大14.7%。（5）湍流理论分析对于提高LAS观测森林生态系统显热通量的准确性具有重要意义。确定了迭代法为该复杂下垫面条件下LAS测算显热通量的计算方法。分析重叠区域印痕权重比值大小以及各风向源区后，建立了适合本观测区域的基于单点通量观测数据扩展到公里观测尺度上的方程为H_ec={0.77f₁/（0.77f₁+0.57f₂）}H_ec1+{0.572f₂/（0.77f₁+0.57f₂）}H_ec2在重叠源区，对由建立的普适函数（FT_JiYuan）计算得到的显热通量（计算值）与涡度相关法观测得到的显热通量（实测值）进行相关性分析，结果表明：二者线性相关系数可达0.90。如采用其他5种广泛应用的普适函数计算显热通量，其计算值与实测值的相关系数为0.27-0.63，说明建立的温度结构参数普适函数具有较高的准确性。更多还原

【Abstract】 The exchange of hydrothermal from land to atmosphere interactions is the most direct andsignificant physical processes, which has been considered to be the important and difficultresearch in the Meteorology, climatology, hydrology, ecology and other related disciplines. Thesensible heat flux （H） is the the driving factors of surface turbulent motion and energyexchange, therefore, it is particularly important to accurately measure regional scale sensibleheat flux. However, due to vegetation above the underlying surface, the flatness of the surface,hydrothermal regime, and weather conditions, it is difficult to solve the problem of technologyof flux measurement and space representation of the data in the kilometer scale.Thelarge-aperture scintillometer （LAS） has greater prospect in measuring a region of severalkilometers and heterogeneous surface-sensible heat fluxes. The parameter that directlyobtained by LAS is the structure parameter of the refractive index of air （C_n²） based on changesin light intensity fluctuation. The structure parameter of temperature （C_T²） is calculated firstly,and then we must select the appropriate universal function for the temperature structureparameter （f_T） according to Monin-Obukhov Similarity Theory （MOST）. The data of C_T²,, f_T of C_T²and zero-plane displacement （z0）, surface roughness （d）, wind velocity （v）, air temperature（T） and any other meteorological data have been used to calculate sensible heat flux withiterative method. MOST could be applied only on homogeneous flat underlying surfaces. Theturbulent motion characteristics of the observed area should be researched to understand firstlywhen we would be ready to calculate sensible heat flux, because that MOST could be appliedonly on homogeneous flat underlying surfaces. But so far, there is no detailed studies reportedin literature.The cork oak, cedar-black and locust was the object in the Hilly North of China. Thequality control theoretical system of the km scale sensible heat flux data was established to verify data quality control and to improve the sensible heat flux estimates of the need foraccuracy. The main conclusions are as follows:（1） There is a strong correlation between turbulence intensity and wind velocity. Theturbulence intensity is the biggest when wind velocity is not more than3m/s.The turbulentintensity of the three wind directions are: I_u=0.326, I_v=0.306, I_w=0.189andI_u=0.324, I_v=0.296, I_w=0.173respectively in two typical time at growing season.（2） The dimensionless standard deviations of turbulent velocity components anddimensionless turbulent kinetic energy （TKE） can be well described by "1/3" power lawrelationships under stable, neutral, and unstable conditions. Land use and land cover changesmainly impact dimensionless standard deviations of horizontal componentuctuations, but theyhave very little effect on those of the vertical component. The dimensionless standarddeviations of wind components and dimensionless; the trend of the vertical wind component isthe opposite. Dimensionless standard deviation of temperature declined with increasing z/Lwith an approximate "-1/3" slope in unstable stratication and "-2/3" slope in stable stratication.Results show that the meteorological elementsMountain in the plantation ecosystem complexsurface conditions obey the Monin-Obukhov similarity theory.The turbulence spectra followed the–5/3power law, and turbulence above the forestcanopy was locally non-isotropic.（3） The best MOST universal function were given byf T_JiYuan=4.91（16.51ζ）^2/3（ζ≡z/L） under unstable conditions andf T_JiYuan=6.43(1+2.20ζ^2/3)under stableconditions.Under unstable conditions and the heat factor （k w’T ’g/T,TT）is less than0.0008, Themeasured value of the degree of dispersion is big; under unstable conditions and TT is greaterthan0.0012, the degree of dispersion is small. The heat factor had significant effect on theapplication of MOST. The heat factor had significant effect on the application of MOST, The values obtainedfrom eddy covariance fluxes by using f T_JiYuanagreed with the values obtained from rawtime series data by using independent methods. MOST can be applied during the interactionbetween heat turbulence and momentum turbulence.TheC2T calculated using the LAS method had a high aggrement with the results given bythe turbulence spectral method, indicating that it was feasible to use the LAS method tomeasure turbulence fluxes over the heterogeneous surface. The accuracy of the selectedappropriate universal function for the temperature structure parameter was high.（4） The source area was relatively larger under stable stratification conditions as a resultof weaker turbulant activity, and was smaller under unstable stratification conditions withstronger turbulant activity. Even the smallest source area under stable stratification conditionwas14.7%bigger than the largest source area under unstable stratification condition. Therefore,spatial representation analysis of measured information should be emphasized under stablestratification condition. Flux information measured by scintiloscope is the most comprehensiveand intact when wind direction almostly perpendicular to optical pathway.（5） The iterative method was determined to caculate sensible heat flux with LAS underthis complex underlying suiface. Considering overlapping area imprint weight and each winddirection source area, the formulation that is suitale for this area to measure flux based on ECflux was expanded to LAS scale,H_ec={0.77f₁/（0.77f₁+0.57f₂）}H_ec1+{0.572f₂/（0.77f₁+0.57f₂）}H_ec2;Correlation analysis was carried out between the sensible heat data caculated by the screenedappropriate universal function and by EC. The result showed that they correlated significantlyand the correlation coefficient between HfECand HLaswas0.9. It proved that the appropriateuniversal function screened for temperature structure parameter has higher accuracy.更多还原