共查询到17条相似文献，搜索用时 125 毫秒
1.
地表能量平衡是地-气间相互作用的重要方式,随着涡旋相关技术在物质传输和能量交换研究中的广泛应用,如何评价其观测数据的可信度则变得尤为重要。利用成都平原温江大气边界层观测站2008年观测资料,分析了农田下垫面上能量收支各分量和辐射平衡各分量的特征及变化规律,并运用最小二乘法(Ordinary Least Squares,OLS)线性回归方法和能量平衡比率(Energy Balance Ratio,EBR)方法对湍流通量(感热与潜热通量之和)与有效能量(净辐射与地表土壤热通量之差)之间的关系进行了研究,得到了一些有意义的结果。 相似文献
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能量平衡分析作为评价涡度相关法通量观测数据可靠性方法，备受学界重视。应用OLS（Ordinary least squares）和EBR（Energy Balance Ratio）2种方法，系统分析了广东省鼎湖山针阔叶混交林生态系统能量平衡特点，并分析各种涡度通量修正方法对能量平衡的影响，结果表明鼎湖山通量站平均能力平衡不闭合度为33％-47％，略高于普遍报道的不闭合度范围（10％-30％）。WPL修正、μ＊订正和坐标转换，使得能量平衡闭合度有所提高，但夜间特别是冬季能量平衡较差问题依然没有得到根本解决，表明夜间弱湍流并不是导致夜间能量平衡闭合度差的主要原因。为客观评价本通量站以及ChinaFLUX能量平衡状况和通量数据质量，确定涡度相关法CO2通量数据分析方法和改进策略提供依据。 相似文献
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近地面层能量不闭合是涡度相关系统观测中普遍存在的难点问题。为了提高涡度相关系统通量观测数据的质量,选取郑州农业气象试验站2009年10月—2010年6月整个冬小麦生长季的通量观测资料,对30 min通量数据进行野点剔除、数据插补和Webb-Pearman-Leuning(WPL)校正等数据预处理。用两种方法(OLS和EBR)评价了该地区麦田生态系统能量平衡状况。结果表明:处理后的数据质量有明显提升,日平均湍流能增加7.09 W·m~(-2),日平均CO2通量减少0.0730 mg·m~(-2)·s~(-1)。农田涡度相关系统观测的能量平衡比率(EBR)日变化规律明显:早晨和傍晚昼夜交替时EBR波动最大,白天能量闭合状况优于夜间;暖季EBR大部分都在1左右浮动,能量平衡闭合程度较高,而冬季能量平衡闭合程度比暖季偏低。能量通量和湍流通量有较强的相关性,决定系数R2=0.8066,能量闭合度为88%,存在能量不闭合现象。 相似文献
4.
半干旱草原下垫面能量平衡特征及土壤热通量对能量闭合率的影响 总被引：3，自引：0，他引：3
土壤热通量在半干旱草原下垫面能量平衡研究中极为重要,土壤热通量估计不够准确是导致地表能量不平衡的一个重要原因。利用2008年6—9月锡林郭勒草原主生长期地表辐射、通量和土壤温度梯度观测资料,研究中纬度半干旱草原下垫面地表能量平衡特征。首先,在分析能量平衡各分量月平均日变化特征的基础上,通过对土壤热流量板观测的5 cm深度土壤热通量(G)的相位前移,研究了土壤热通量相位滞后对地表能量平衡产生的影响;其次,利用谐波分析方法,通过计算地表土壤热通量(Gs),分析了地表到热流量板之间的土壤热量储存对地表能量平衡的影响。结果表明:(1)将土壤热通量相位前移30 min,湍流通量与可利用能量(Rn-G)线性回归的斜率从0.835增加到0.842,地表能量闭合率提高了0.7%,但仍有15.8%的能量不闭合;(2)考虑了地表到热流量板之间的土壤热量储存之后,湍流通量与可利用能量之间的回归斜率达到0.979,能量不闭合程度仅为2.1%。 相似文献
5.
利用兰州大学半干旱气候与环境观测站(SACOL)2008年夏季的观测资料,分析了陇中黄土高原地表能量不平衡特征及其影响机制,计算了地表和5 cm深处土壤热通量板之间的热储存,并对地表能量不平衡特征重新进行了计算和评价。当把土壤热储存作为地表能量收支的一部分考虑后,不平衡差额绝对值平均降低了23 W.m-2,能量不闭合度平均减小了0.104,利用最小二乘法(OLS)进行线性回归得到的平均不闭合度减小了0.085。从白天和晚上的能量不闭合度频率分布也能够看出,土壤热储存对地表能量收支平衡有很大改善。但即使考虑了土壤热储存项,地表能量不闭合仍然很明显。除了土壤热储存,边界层大气不同形式的输送能力作为对地气能量通量交换过程中的重要因素,对能量不平衡也会产生深远影响。结果显示,地表能量不闭合度分别与垂直速度w、水平风速u和对流速度尺度w*有较密切的关系。涡动相关法通量计算中常通过坐标旋转强迫垂直速度变为零,然而非零的垂直速度和垂直平流是真实存在的,忽略垂直平流热量输送是产生地表能量不平衡的重要原因。 相似文献
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疏勒河上游高寒草甸下垫面湍流特征分析 总被引：3，自引：0，他引：3
利用2011年疏勒河上游高寒草甸生长季(5-9月)的近地层湍流观测资料,分析了该区域近地层三维风速标准差统计特征及近地层能量交换特征.结果表明,研究区域无量纲化三维风速标准差与稳定度的关系满足Monin-Obukhov相似理论;在近中性条件下,高寒草甸下垫面无量纲化三维风速标准差近似表现为一常数,即σu/u*=3.50,σv/u*=3.30,σw/u*=0.96;通过最小二乘法(OLS)的回归直线,5-9月强制通过原点的OLS回归斜率分别为0.76,0.72,0.75,0.73和0.73;能量平衡比率(EBR)月平均值分别为0.90,0.85,0.86,0.88和0.93;能量闭合度白天大于夜间,EBR从早晨到下午呈增加趋势,并在日出和日落时段变化较为剧烈.在生长季节研究区净辐射主要消耗于潜热即研究区的蒸散,其次是陆地与大气间的感热交换,最后是地表热通量. 相似文献
9.
为了研究湍涡对中尺度绿洲灌溉的响应,利用WRF模式大涡模拟模块（WRF-LES）在西北半干旱区绿洲区开展灌溉前和灌溉后两个大涡模拟试验（分别简称为BI和AI）,其中灌溉可能会改变绿洲非均匀强度。利用面积平均的办法计算湍流热通量并利用小波分析将湍流热通量模态分解到不同的尺度。结果表明灌溉增加了土壤湿度,引起绿洲内部非均匀强度增加,灌溉对垂直热通量以及通量频散都有较大影响。AI中的湍涡为网状,与BI中一致。AI与BI中的感热通量的频散高度都随着感热通量的减小而减小。AI与BI中感热通量小波能量谱尺度一致,但是BI中强度比AI小。潜热通量的频散高度依赖于感热通量,且潜热通量能量谱随高度减小。空间滞后相关系数的结果表明由于灌溉前地表加热较强,感热通量对地表热通量的响应高度在灌溉之前（BI）比灌溉后（AI）更高。灌溉后的通量模态的飘移距离小于灌溉前的。 相似文献
10.
对青藏高原地区地表能量的研究是一个十分重要的问题.利用中国科学院珠穆朗玛峰大气与环境综合观测研究站2006年5月至2007年4月一年的观测资料,分析了青藏高原珠峰地区的地表能量,即净辐射通量、感热通量、潜热通量和土壤热通量,得到了一些有关珠峰地区地表能量的结果,即太阳总辐射、大气长波辐射、地面长波辐射和净辐射呈现出明显的年变化特征,净辐射、感热通量、潜热通量和土壤热通量得到的日变化是很明显的.并且讨论了计算地表能量通量的方法及其优缺点. 相似文献
11.
Soojin Kim Young-Hee Lee Kyu Rang Kim Young-San Park 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(1):553-565
Surface energy balance closure has been examined using eddy covariance measurements and other observations at one industrial and three agricultural sites near the Nakdong River during daytime. Energy balance closure was evaluated by calculating the long-term averaged energy balance ratio (EBR), the ratio of turbulent energy fluxes to available energy, and the statistical regression of turbulent energy fluxes against available energy using half-hourly data. The EBR of all sites ranges from 0.46 to 0.83 while the coefficient of determination (R 2) ranges from 0.37 to 0.77. The energy balance closure was relatively poor compared to homogeneous sites, indicating the influence of surface heterogeneity. Unmeasured heat storage terms also seem to play a role in the surface energy budget at the industrial and irrigated sites. The energy balance closure was better in conditions of high wind speed, low downward short wave radiation, and high friction velocity, which suggests the role of heat storage term and surface heterogeneity in surface energy balance at these sites. Spectrum analysis shows a sharp roll-off at the low frequency in co-spectrum, which indicates that low-frequency motions do not significantly contribute to turbulent fluxes. Both the spectra and cospectra in unstable conditions show a broad peak indicating the influence of multiple sizes of large eddies over heterogeneous sites. Most of ogive curves for the kinematic latent and sensible heat fluxes reach an asymptote within 30 minutes regardless of the EBR value, indicating that low frequency motion is not a main factor for energy imbalance. However, stationary eddies due to landscape heterogeneity still remains as a possible cause for energy imbalance. 相似文献
12.
Guillermo Hernandez-Ramirez Jerry L. Hatfield John H. Prueger Thomas J. Sauer 《Theoretical and Applied Climatology》2010,100(1-2):79-92
Quantifying the energy balance above plant canopies is critical for better understanding of water balance and changes in regional weather patterns. This study examined temporal variations of energy balance terms for contrasting canopies [corn (Zea mays L.) and soybean (Glycine max L. Merr.)]. We monitored energy balance for 4 years using eddy-covariance systems, net radiometers, and soil heat flux plates in adjacent production fields near Ames, Iowa. On an annual basis, soybean exhibited 20% and 30% lower sensible heat flux (H) and Bowen ratio than corn, respectively. As canopies developed, a gradual shift in turbulent fluxes occurred with decreasing H and increasing latent heat flux (LE), but with a more pronounced effect for corn. Conversely, during mid-growing season and as both canopies progressively senesced, H in general increased and LE decreased; however, soybean exhibited slightly greater LE and much lower H than corn. These temporal variations in magnitude and partitioning of turbulent fluxes translated into a pronounced energy imbalance for soybean (0.80) and an enhanced closure for corn (0.98) in August and September. These discrepancies could be directly associated with differences in momentum transport as shown by friction velocities of 0.34 and 0.28 m s?1 for corn and soybean, respectively. These results support influential roles of plant canopy on intensity and mode of surface energy exchange processes. 相似文献
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均匀裸土地表土壤热通量计算方法对比及对能量闭合的影响 总被引：2，自引：1，他引：1
利用"内蒙古微气象观测蒸发试验"的观测资料,对6种地表土壤热通量计算方法(Plate Cal法、TDEC法、谐波法、热传导对流法、振幅法和相位法)进行比较,检验了6种方法在不同干湿地表状况下的适用性,并研究了6种方法计算地表土壤热通量的差异以及对地表能量闭合度的影响。结果表明:一般情况下,Plate Cal法计算的2 cm土壤热通量与观测值最接近,计算结果的均方差为6.9 W/m2。在不同干湿地表状况下,干燥和降水条件下适合使用Plate Cal法,计算结果的均方差分别为14.0 W/m2和30.1 W/m2;湿润条件下适合使用谐波法,计算结果的均方差为21.4 W/m2。6种方法计算的地表土壤热通量存在明显差别,最大相差178.6 W/m2,不同方法计算地表土壤热通量的最大差值超过25 W/m2的时次占样本的96.3%。不同方法计算地表土壤热通量的差异对地表能量闭合度的大小有明显影响,但不影响近地层能量闭合度随湍流混合增强而增大的规律。 相似文献
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利用长白山森林生态系统定位研究站观测资料,及2003年8月和9月涡旋相关资料,分析和比较了该地区近地层包括风速、风向、大气稳定度在内的平均场特征,以及湍流强度、无量纲化风脉动方差相似性和地表通量变化特征。结果表明:(1)8月和9月稳定度都基本集中在0附近;(2)风速2 m·s-1的环境中,湍流发展最为旺盛,随着风速的增大湍流强度先迅速减小,当风速增大到3 m·s-1后,湍流强度偏离0值变大了一些,再继续增大到一定风速大小以后,湍流强度基本不随风速变化;(3)无量纲化三维风脉动方差符合Monin-Obukhov相似理论的"1/3"定律,其最佳通用相似函数在稳定和不稳定条件下都可以拟合得到;(4)地表通量均表现出明显的日变化特征,8月以潜热为主,感热较小;9月仍以潜热为主,但是相比8月明显偏小,感热变化不大。 相似文献
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中国西北干旱区戈壁下垫面夏季的热力输送 总被引：6，自引：1，他引：5
以敦煌戈壁站2004年6月和2008年8月的常规观测和超声观测为例,分析了西北干旱区戈壁下垫面夏季热力输送的一般过程及特征。首先评价了湍流通量的观测质量以及仪器观测的地表能量通量闭合问题,结果表明敦煌戈壁站的观测在白天总体较好。夏季地表能量通量的平均日变化显示,潜热通量整天都很小,可以忽略,白天到达地表的短波辐射以及地表向上的长波辐射非常强,地表净辐射主要转化为感热输送（敦煌戈壁站在中午时平均分别达380W·m-2以上和250W·m-2以上）;夜间土壤释放热量以平衡地表的辐射冷却,感热通量略低于0。白天时地表大气经常触发自由对流活动,影响动量通量的观测质量,并有效输送地表热力至上层大气中,有助于形成超厚大气边界层。分析了戈壁下垫面的动量粗糙度特征和热力粗糙度特征（敦煌戈壁站动量粗糙度约为0．6mm）,热力粗糙度基本小于动量粗糙度一个量级,这符合目前对干旱区戈壁下垫面热力输送特征的初步认识。 相似文献
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Effects of the soil heat flux estimates on surface energy balance closure over a semi-arid grassland 
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下载免费PDF全文 Soil heat flux is important for surface energy balance (SEB), and inaccurate estimation of soil heat flux often leads to surface
energy imbalance. In this paper, by using observations of surface radiation fluxes and soil temperature gradients at a semi-arid
grassland in Xilingguole, Inner Mongolia, China from June to September 2008, the characters of the SEB for the semi-arid grassland
were analyzed. Firstly, monthly averaged diurnal variations of SEB components were revealed. A 30-min forward phase displacement
of soil heat flux (G) observed by a fluxplate at the depth of 5-cm below the soil surface was conducted and its effect on the SEB was studied.
Secondly, the surface soil heat flux (G
s) was computed by using harmonic analysis and the effect of the soil heat storage between the surface and the fluxplate on
the SEB was examined. The results show that with the 30-min forward phase displacement of observed G, the slope of the ordinary linear regression (OLR) of turbulent fluxes (H+LE) against available energy (R
n-G) increased from 0.835 to 0.842, i.e., the closure ratio of SEB increased by 0.7%, yet energy imclosure of 15.8% still existed
in the SEB. When G
s, instead of G was used in the SEB equation, the slope of corresponding OLR of (H+LE) against (R
n-G
s) reached 0.979, thereby the imclosure ratio of SEB was reduced to only 2.1%. 相似文献
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Mapping of Land-Atmosphere Heat Fluxes and Surface Parameters with Remote Sensing Data 总被引：3，自引：0，他引：3
A variational data assimilation scheme is used to infer two key parameters ofthe surface energy balance that control the partitioning of available energy intolatent, sensible, and ground heat fluxes (LE, H, and G). Remotely sensedland surface temperature (LST) is the principal data source. Maps ofdiurnal energy balance components are presented for a basin with varied landcover (Arno Basin, Italy) for a 18-day period in July 1996.Given available energy, the major unknown (dimensionless) parameters requiredfor partitioning among fluxes are: (1) Landscape effects on near-surfaceturbulence as captured by the bulk heat transfer coefficient CBN underneutral conditions and (2) surface control of the relative magnitudes of LEand H as represented by the evaporative fraction EF. The data assimilationscheme merges 1.1-km resolution remotely sensed LST images (based onoptical, thermal and microwave measurements from two different satelliteplatforms) into a parsimonious model of heat diffusion. Both the measurementsand the model predictions are considered uncertain. Posterior error statisticsthat represent uncertainty of the estimated parameters are also derived.Maps of CBN show spatial patterns consistent with the dominant land useand basin physiography. Daily maps of EF exhibit spatial variationscorresponding to land cover and land use – the day-to-day variations inEF show fluctuations consistent with rain events and drydowns experiencedduring the period. Based on these parameters and available environmentalvariables, maps of diurnal LE and H may be produced (in this paper daytimeLE maps are reported).The application demonstrates that remotely sensed land surface temperaturesequences contain significant amount of information of the partitioning ofavailable energy among the fluxes. The variational data assimilation frameworkis shown to be an efficient and parsimonious approach without reliance onempirical relationships such as those based on vegetation indices. 相似文献