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1.
安吉毛竹林生长季土壤热通量的变化特征   总被引：1，自引：0，他引：1  
2011年4月~2011年9月运用常规气象观测仪器和土壤热通量板对浙江安吉毛竹林土壤热通量和气象因子进行观测,探讨了生长季土壤热通量的变化特征以及土壤温度、净辐射与土壤热通量的关系。结果表明:土壤热通量日变化均呈"S"型曲线,毛竹林生长季土壤热通量为58.914 WJ m-2,土壤为明显的热汇;越接近地表,土壤温度月变化越剧烈;不同时间尺度上,土壤5 cm温度与土壤热通量的回归分析,相关性均达显著水平,说明土壤温度变化是以热通量为基础的;在0.5 h尺度上,土壤热通量与净辐射的相关性达极显著水平(P0.001),且延滞1 h后的相关系数最高,说明安吉毛竹林生长季土壤热通量对净辐射的反馈要延滞1 h。  相似文献   

2.
亚热带毛竹林土壤热通量变异特征   总被引：1，自引：0，他引：1  
孙成  江洪  陈健  王彬  刘玉莉  陈雅奇 《土壤学报》2013,50(5):966-973
选取2010年12月1日—2011年11月30日的土壤热通量实测数据,通过研究,分析了亚热带（浙江省）毛竹林土壤热通量与三层土壤温度、三层土壤含水量以及净辐射的关系。结果表明：土壤热通量有明显的季节变化特征,而日变化均为“S”形,有一个峰值和一个谷值,月均值差异较明显。年尺度上土壤是热源,土壤热通量为-7.52 MJ m-2,占全年净辐射的-0.289%,正向最大值出现在7月（18.71MJ m-2）,负向最大值出现在1月（-19.33MJ m-2）。不同时间尺度和不同土壤深度进行回归关系分析,在月尺度上,土壤热通量与土壤5 cm温度的相关性最好,达极显著水平;在日尺度上,土壤热通量与土壤5 cm含水量相关性达极显著水平,但相关系数不高;在月尺度上月均值土壤热通量与净辐射极显著相关,在半小时尺度上相关性也为极显著水平,且时间上无延滞现象。  相似文献   

3.
用气象资料计算参照作物腾发量(ET0)的方法需要各种气象(候)和物理参数,净辐射是其中的重要数据之一,而专业测量净辐射的设备在农业气象站里很少安装。为解决计算ET0时缺少太阳净辐射(Rn)测量值这一实际问题,该文采用浑善达克沙地东南缘南沙梁草甸草原区气象站观测的气象资料,用遗传算法模型对联合国粮农组织56号文本(FAO56)推荐值(as和bs)进行率定,计算了对应夏半年(4—9月)和冬半年(1—3月和10—12月)的太阳净辐射和参照作物腾发量,并将率定前后的模拟太阳辐射进行对比分析,用残差估计指数法对该方法模拟的参照作物腾发量模拟精度进行了分析。结果表明:在缺少太阳净辐射测量值的地区,采用FAO56参数(as和bs)推荐值与遗传算法模型率定参数(as和bs)相比,净辐射年内变化趋势一致,采用率定后参数计算的净辐射相对更不稳定,波动更大,但能有效提高参照作物腾发量计算精度。误差较大的模拟值均出现在降雨日前后,降雨虽然并未直接出现在Penman-Monteith公式中,但是降雨必然会对湿度和温度等气象条件造成一定影响,而as和bs是受湿度等因素影响而变化的,其深层次的原因有待进一步分析。  相似文献   

4.
对祁连山海北地区矮嵩草(Kobresia humilis)草甸和金露梅(Potentilla fruticosa)灌丛草甸两种植被类型土壤热通量观测和比较分析发现:晴天两种植被类型区土壤热通量日变化均表现为单峰型,夜间低午后高;阴雨天土壤热通量变化复杂,随降水或云层厚薄波动剧烈。金露梅灌丛草甸土壤热通量的日变化较矮嵩草草甸更为平稳。两种草甸土壤热通量的月际变化同样表现为单峰型,12月最低(矮嵩草草甸和金露梅灌丛草甸分别为-40.27MJ/m2和-16.85MJ/m2)、6月最高(矮嵩草草甸和金露梅灌丛草甸分别为20.47MJ/m2和18.98MJ/m2)。矮嵩草草甸与金露梅灌丛草甸土壤热通量的年总量差异明显,分别为-24.72MJ/m2和48.10MJ/m2。表现出前者由土壤深层向地表散热,而后者由地表向土壤深层输送热量。两种植被类型区不同时间尺度上的土壤热通量与冠层净辐射均有显著的线性相关关系。由于冠层厚度的影响,金露梅灌丛草甸土壤热通量所占净辐射的比例较小,同步性较差,反馈延时约2.5h,而矮嵩草草甸的土壤热通量与净辐射的相关性更加密切。  相似文献   

5.
亚热带红壤丘陵区水稻田净全辐射初探   总被引：2，自引：0，他引：2  
对中国科学院千烟洲试验站水稻田与气象站的辐射观测数据进行初步分析结果表明,我国亚热带红壤丘陵区水稻田净全辐射和太阳总辐射最高值出现在地方时的１１：００～１３：００,日出后和日落前１ｈ左右通过０点;夜间总辐射为０Ｗ／Ｍ＾２,净辐射一般变动在０～－１００Ｗ／ｍ＾２之间。农田与气象站总辐射和净辐射之间存在极显著的线性,根据气象站总辐射、净全辐射观测数据与利用拟合方程估算不同水稻田的相应数值。水稻田与气象  相似文献   

6.
显热通量（sensible heat flux，H）是反映地表湍流运动的重要参数，准确获取该参数对于区域内热量交换规律的认识和农业生产及水资源的有效管理具有重要意义。涡动相关仪（eddy covariance system，EC）和大孔径闪烁仪（large aperture scintillometer，LAS）是目前生态系统水热通量的主要测量手段，但两者观测范围的空间尺度存在差异。该研究以呼伦贝尔草甸草原生态系统为对象，通过对比分析两种方法观测的显热通量（HLAS和HEC）变化特征，对两者之间的差异（ΔH）及产生原因进行探究，并且定量研究了不同因子对ΔH的影响程度。结果表明，在不同时间尺度内，HLAS和HEC的变化趋势基本一致，显热通量主要受到净辐射的驱动作用，同时ΔH与净辐射存在正相关性；对应时刻HLAS和HEC之间线性回归方程斜率为1.13，拟合优度R2为0.81，说明大孔径闪烁仪在草甸草原区有着很好的适用性；EC能量平衡闭合程度会影响HLAS和HEC之间差异，剔除能量平衡闭合率（energy balance ratio，EBR）小于0.8的数据后，HLAS和HEC之间线性回归方程斜率减小至1.05，说明能量平衡闭合程度越高ΔH越小；净辐射（net radiation，Rn）、风速（wind speed，WS）、波文比（Bowen ratio，Bowen）和饱和水汽压差（saturated water vapor pressure difference，VPD）与ΔH之间相关性显著，是ΔH的主要气象环境因子；ΔH单个影响因子的解释能力从高到低依次为净辐射、风速、EC能量平衡闭合率、饱和水汽压差、波文比，任意两个不同影响因子之间均呈现双因子增强作用，解释能力较高的交互影响因子为净辐射/风速和风速/波文比。研究结果有利于准确理解LAS与EC显热通量观测过程中的空间尺度效应，同时可为区域尺度扩展和遥感地面验证过程中通量数据的质量控制提供科学参考依据。  相似文献   

7.
几种常用净辐射计算方法在黄淮海平原应用的评价   总被引：4，自引：2，他引：4  
Penman修正式和FAO Penman-Monteith公式是利用气象资料计算参考作物蒸散量方法中应用最广泛的。这些公式中净辐射是根据温度、日照时数、湿度以及一些当地的参数来计算的。用实测数据评价净辐射计算方法的研究还很少。该文作者利用中国科学院禹城综合试验站实测数据对两个公式中净辐射计算方法在黄淮海平原的应用进行了评价。在Penman修正式中，别尔良德法、彭曼法、布朗特法和邓根云法是常用的净长波辐射计算方法。结果表明：在Penman修正式净辐射公式中，采用别尔良德净长波计算方法误差最小，而且与FAO Penman-Monteith公式中净辐射计算精度一致，但都存在相对误差在11～1月份比其他月份偏大的现象。进一步建立了适合本地区的用总辐射推算净辐射的经验公式。  相似文献   

8.
对中国科学院千烟洲试验站水稻田与气象站的辐射观测数据进行初步分析结果表明,我国亚热带红壤丘陵区水稻田净全辐射和太阳总辐射最高值出现在地方时的1100～1300,日出后和日落前1h左右通过0点;夜间总辐射为0W/m  相似文献   

9.
准确测算和模拟农田潜热通量对农业生产有着重要意义。该研究基于波文比能量观测系统对苏南地区夏玉米和冬小麦生育期内潜热通量进行连续观测,采用Katerji-Perrier（KP）和Todorovic（TD）两种方法来确定Penman-Monteith（P-M）模型中冠层阻力参数,探究两种冠层阻力参数子模型的估算误差及成因。结果表明：冬小麦生育期内主要气象因子呈现相似变化趋势,净辐射日均值呈现出波动上升趋势。两种冠层阻力参数子模型对冬小麦潜热通量模拟均取得良好的模拟效果,模拟R2不小于0.84,纳什系数不小于0.86,但KP模型精度稍高于TD模型。KP模型对冬小麦和夏玉米潜热通量均有高估,而TD模型高估了夏玉米潜热通量,饱和水汽压差是影响KP和TD两种冠层阻力参数子模型误差的主要因素,且饱和水汽压差越大绝对误差越大。研究为当地农业用水管理提供科学依据。  相似文献   

10.
半干旱风沙草原区草地潜热通量的特征   总被引：5，自引：1，他引：5  
半干旱风沙草原区是北方的主要生态系统类型,对调节局地和全球气候具有重要意义.蒸散作为热量和水量平衡的重要分量,是该生态系统水分损失的主要途径,在水分平衡中占有重要地位.本文利用开路涡度相关系统和常规气象梯度观测系统对科尔沁半干旱风沙草原2007年9月1日-26日的蒸散量和微气象条件进行了观测,根据观测得到数据分析了观测系统的能量平衡闭合状况,探讨了潜热通量与气象因子之间的关系.结果表明,观测系统的能量平衡闭合度为82.7%,处于国内外同类观测闭合度范围的中上水平.30min的潜热通量与净辐射数据之间呈线性相关关系,潜热通量日变化特点是白天高于夜间,中午时刻最高,净辐射与潜热通量每日峰值同时出现,温度、饱和差的峰值比潜热通量峰值滞后2～3h,潜热通量峰值时刻的空气相对湿度处于一日内最低,此季潜热通量平均日总量为5.44MJ*m-2,相当于2.21mm蒸散量,潜热日总量与净辐射日总量呈指数关系.  相似文献   

11.
Various methods exist to measure soil pH, and while there is general agreement between the existing published laboratory and field-based methods, the latter are subject to uncertainties including test kit reliability, accuracy, precision, and environmental factors. The contribution of this study is to quantify three uncertainties that affect the conversion between field pH and laboratory pH measurements, namely operator experience, choice of test kit, and the time-of-day for measurement. Soil samples from western Victoria, representing the pH range 4.5–10.0, were used in a randomized complete block design with 10 assessors split into two groups representing experienced and inexperienced users. Statistical analysis of laboratory and field pH was based on using the Maximum Likelihood Functional Relationship (MLFR) to determine if there was any bias between the two methods. Significant differences were found between experienced and inexperienced users, and between test kits.  相似文献   

12.
Estimates of data uncertainties are required to integrate different observational data streams as model constraints using model-data fusion. We describe an approach with which random and systematic uncertainties in optical measurements of leaf area index [LAI] can be quantified. We use data from a measurement campaign at the spruce-dominated Howland Forest AmeriFlux site for illustrative purposes. We made measurements along two transects (one in a mature stand, one in a recently harvested shelterwood) before sunset on successive days using both the Li-Cor LAI-2000 plant canopy analyzer and digital hemispherical photography (DHP). The random measurement uncertainty (1σ) at a given point for a single measurement is about 5% for LAI-2000 and 10% for DHP. These uncertainties are small compared to potential systematic biases due to instrument calibration errors and data processing decisions, which are estimated to be 10-20% for each instrument. Sampling uncertainty (due to the spatial variability along each transect where we conducted our measurements) is an additional, but again relatively small, uncertainty. Assumptions about clumping parameters, for which standard literature values are typically used, remain large sources of uncertainty. This analysis can also be used to develop strategies to reduce measurement uncertainties.  相似文献   

13.
The results of 20 yr of measuring γ-HCH in precipitation in The Netherlands are presented here. Analysis has revealed a systematic seasonal behaviour, with enhanced levels of γ-HCH in precipitation from April through June. A statistically significant change in concentrations during the last 20 yr was found. An evaluation of measurement results from north-west Europe confirms the large-scale distribution of γ-HCH in precipitation in that region. Long time series of γ-HCH measurements are a useful tool in evaluating its emission trend. Given the large uncertainties in emission estimates and in modelling of atmospheric transport and deposition up to now, measurements are considered to be a better tool for monitoring the changes in environmental levels of γ-HCH.  相似文献   

14.
Manual closed‐chamber measurements are commonly used to quantify annual net CO2 ecosystem exchange (NEE) in a wide range of terrestrial ecosystems. However, differences in both the acquisition and gap filling of manual closed‐chamber data are large in the existing literature, complicating inter‐study comparisons and meta analyses. The aim of this study was to compare common approaches for quantifying CO2 exchange at three methodological levels. (1) The first level included two different CO2 flux measurement methods: one via measurements during mid‐day applying net coverages (mid‐day approach) and one via measurements from sunrise to noon (sunrise approach) to capture a span of light conditions for measurements of NEE with transparent chambers. (2) The second level included three different methods of pooling measured ecosystem respiration (RECO) fluxes for empirical modeling of RECO: campaign‐wise (19 single‐measurement‐day RECO models), season‐wise (one RECO model for the entire study period), and cluster‐wise (two RECO models representing a low and a high vegetation status). (3) The third level included two different methods of deriving fluxes of gross primary production (GPP): by subtracting either proximately measured RECO fluxes (direct GPP modeling) or empirically modeled RECO fluxes from measured NEE fluxes (indirect GPP modeling). Measurements were made during 2013–2014 in a lucerne‐clover‐grass field in NE Germany. Across the different combinations of measurement and gap‐filling options, the NEE balances of the agricultural field diverged strongly (–200 to 425 g CO2‐C m−2). NEE balances were most similar to previous studies when derived from sunrise measurements and indirect GPP modeling. Overall, the large variation in NEE balances resulting from different data‐acquisition or gap‐filling strategies indicates that these methodological decisions should be made very carefully and that they likely add to the overall uncertainty of greenhouse gas emission factors. Preferably, a standard approach should be developed to reduce the uncertainty of upscaled estimates.  相似文献   

15.
Net radiation (Rn) is the sum of the radiant energy at the Earth's surface and is a major component of the surface energy balance. However, Rn is difficult to measure accurately, and multiple instruments are available to measure it. Two new instruments (Hukseflux Thermal Sensors B.V., model NR01; Kipp & Zonen B.V., model CNR 2) have been released within the past two years. We compared these models, two less-expensive older models (Kipp & Zonen B.V., model NR-Lite; Radiation and Energy Balance Systems, Inc., model Q*7.1), and a more expensive older model (Kipp & Zonen B.V., model CNR 1) over a uniform turfgrass surface for 33 days in mid-summer. Three replicates of each radiometer were included in the study (except for the CNR 1). The instruments that independently measure the four components of Rn (models CNR 1 and NR01) were typically the most accurate. Incoming shortwave measurements from the four component instruments were compared to a reference pyranometer, and outgoing longwave measurements were compared to infrared measurements of surface temperature. The differences from the reference pyranometer and surface temperature measurements were typically 2% or less. There was a difference of approximately 5% in incoming longwave measurements between these two radiometer models. This is likely due to differences in calibration approaches, which are discussed. This emphasizes the need for standardization of longwave calibration methods and establishment of a world reference for longwave radiation. The instruments that do not separate shortwave and longwave radiation into component measurements (net all-wave radiometers, models NR-Lite and Q*7.1) were generally the least accurate, and had offsetting day and night differences that reduced daily total Rn differences relative to the reference. The CNR 2 measures net shortwave and net longwave, and is an intermediate between a four component instrument and a net all-wave instrument. The Rn measurement accuracy of the CNR 2 typically fell between that of the two groups. Differences among radiometers tended to be larger at night than during the day, indicating higher variability in longwave measurements. An inversion (flip) test in the field showed the NR-Lites and Q*7.1s had well matched detectors, however two of the three replicate CNR 2s had mismatch errors greater than 5%. This becomes important for measurements over non-vegetated surfaces. The data presented here should be helpful in selecting the most cost effective instrument for a given application.  相似文献   

16.
Parameters of first‐order mineralization models are commonly estimated from incubation experiments by using nonlinear estimation techniques. The impact of incubation length and especially more or less small measurement errors on estimated mineralization parameters is largely unknown. The objective of this paper is to analyze the influence of errors in mineralization measurements on the nonlinearly estimated parameters, and to find out how the certainty of parameters can be enhanced. CO2 evolution from organic material (forest floor, L layer) of an acid sandy podzol under pine (Pinus silvestris L.) is taken as an example. For the nonlinear parameter estimation, Marquardt's method is used, and to evaluate uncertainties of estimated model parameters, Monte‐Carlo simulations are performed. The results demonstrate that really small measurement errors in the order of random and unavoidable experimental errors may cause serious uncertainties (about 50 %) in the estimated parameters. Parameter uncertainties are the same for cumulative or rate measurements and models. The evaluations based on Monte‐Carlo simulations show that measurement accuracy and incubation length are key factors for the certainty of estimated parameters. Any decrease of measurement errors results in a disproportionate enhancement of parameter certainty. An increase of incubation length up to about 80 % of the time needed to reach 90 % of the maximum cumulative mineralization, t90, is optimal to minimize parameter uncertainty. This optimal incubation length is commonly not known a priori because t90 depends on the a priori unknown mineralization kinetics. A practical way for its determination is an accompanying estimation of the parameters while the incubation is going on, and the experiment may be terminated when incubation length has reached about 80 % of the estimate of t90.  相似文献   

17.
The Electric Power Research Institute (EPRI) and the United States Environmental Protection Agency (EPA) have carried out joint tests for validation of EPA (Draft) Method 29 (“multi-metals method”) for measurement of mercury (Hg) and other selected metals in the stack gas of a coal-fired electric utility. The tests were performed according to the “analyte spiking” procedure of EPA Method 301 protocol for the field validation of stationary source emission measurements. Several other Hg measurement methods were also employed during the tests to provide a comparison to the Method 29 measurements; these included EPA Method 101A, the Hazardous Element Sampling Train (HEST), and two solid sorbent methods, one using activated charcoal and the other using iodated carbon traps in series with soda lime traps. Results indicate reasonably good agreement between the total Hg measurements by the different methods.  相似文献   

18.
Iron (Fe) is an essential nutrient for plants. When Fe‐deficient, most dicotyledonous and non‐graminaceous monocotyledonous plants exhibit Fe‐deficiency stress responses, which may include proton (H+) release from roots. Proton release is considered to be one of the factors contributing to plant Fe‐deficiency resistance. Several methods, including the pH‐stat, back‐titration, and pH‐drift procedures, have been used to evaluate the Fe‐deficiency induced acidification process. These methods actually determine total net acidity release, not H+ release. A method, based on the principles of chemical equilibrium, for the analysis of net free H+ release is introduced in this paper. By comparing results of the chemical equilibrium method with those of a method measuring total net acidity release, such as the back‐titration method, it is possible to determine the relative role of free H+ and organic acid to total acidity release. The pH‐stat method for analysis of total net acidity release, in which the pH of the incubation solution is held constant, eliminates the influence of pH decrease during plant incubation and thus results in a more accurate measurement of Fe‐deficiency induced acidity release. The advantages and disadvantages of each individual method are discussed.  相似文献   

19.
Based on Soil Plant Analysis Development (SPAD) values, nitrogen (N) deficiency, nutrient need, and the effect of fertilizer treatments on crop conditions can be quickly estimated, but the method of SPAD measurement significantly affects the accuracy of estimation. In field experiments near Debrecen, Hungary, we measured the reliability and accuracy of SPAD measurements in maize and potato populations using a Minolta SPAD-502 meter (Minolta, Tokyo, Japan). The aim of our study was to determine which SPAD measurement methods are capable of detecting small differences in the SPAD values. During the examination of maize ear leaves, we determined the distribution of SPAD values along the leaf blade and then identified single- and multipoint measurement methods. By comparing the results of the measurement methods we established that the single-point-based measurements are less suitable for the determination of the average SPAD value of the leaf blade than the multipoint-based measurements. Also, we showed that the increase in the number of measurement points does not influence the accuracy of the measurement in the case of systematic measurement methods based on the distribution of SPAD values. Thus we recommend five-point measurements to obtain the average SPAD values of the ear leaves: the tip of the leaf blade and at one quarter and one half of the leaf blade from the base on both the right and left sides. From the measurements conducted in potato, we showed that the SPAD values change at every foliar level and that the measurements carried out on the middle foliar level provide the closest correlation with the average SPAD values of the leaf canopy. Based on these results, we recommend making measurements at different foliar levels or on the middle foliar level to determine the average SPAD value of the potato leaf canopy.  相似文献   

20.
The use of a laboratory-scale mixer for predicting the mixing requirement of flours in an industrial-scale mixer was investigated by measuring the work input required to mix a range of flours to peak consistency on both a laboratory-scale and an industrial-scale mechanical dough development (MDD) mixer. The industrial mixer used was a Tweedy-type mixer, and the mixing optimum was determined using a probe that sensed changes in dough consistency. Work input was estimated from mixer motor power, taking into account expected motor and drive chain losses, and from dough temperature rise measurements. The laboratory mixer used twin flat-bladed rotors; mixing optimum and work input were determined from the torque measurement. Work inputs from both mixers were highly correlated (r2 = 0.88) but with a large offset (the industrial mixer requiring more work to develop the dough). The two methods of measuring industrial mixer work inputs gave slightly different results leading to uncertainty as to the actual work given by the industrial mixer. Farinograph mixing properties were less well correlated with industrial-scale work input requirement than the laboratory-scale MDD mixer.  相似文献   

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