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1.
The sensible heat loss from a stand of winter wheat was calculated from radiometric measurements of crop surface temperature, measurements of air temperature, and an atmospheric resistance to momentum transfer; corresponding latent heat flux was obtained through the energy balance equation. These estimates of sensible and latent heat were compared with fluxes from the Bowen Ratio method. When radiative temperature was derived using a measured canopy emissivity of 0.98, calculations of sensible heat flux were systematically 50–100 W m-2 less than Bowen Ratio values. The two techniques agreed more closely when an apparent emissivity of 0.96 was used with an apparent reflectivity of 0.03. The mean difference between the estimates of latent heat flux was then -16 ± 32 W m-2.The surface temperature method showed less systematic error in comparison with the Bowen Ratio values than did estimates using the aerodynamic method.On leave from: University of Nottingham, School of Agriculture, Loughborough LE12 5RD. 相似文献
2.
During slightly unstable but still very close to neutral conditions new results from two previous investigations have shown
a significant increase of sensible and latent heat fluxes over the sea. The vertical heat transport during these conditions
is dominated by detached eddies originating at the top of the boundary layer, bringing relatively cold and dry air to the
surface. This effect can be described in numerical models by either enhanced heat transfer coefficients for sensible and latent
heat (Stanton and Dalton numbers respectively) or with an additional roughness length, added to the original roughness lengths
for heat and humidity. Such new expressions are developed using turbulence measurements from the Baltic Sea valid for wind
speeds up to 14 m s−1. The effect of including the increased heat fluxes is investigated using two different numerical models: a regional three-dimensional
climate model covering northern Europe, and a process-oriented ocean model for the Baltic Sea. During periods of several days,
the latent heat flux can be increased by as much as 100 W m−2. The increase in sensible heat flux is significantly smaller since the process is only of importance in the very near-neutral
regime where the sensible heat flux is very small. The long-term average effect over the Baltic Sea is of the order of several
W m−2. 相似文献
3.
A. J. Pitman A. Henderson-Sellers C. E. Desborough Z.-L. Yang F. Abramopoulos A. Boone R. E. Dickinson N. Gedney R. Koster E. Kowalczyk D. Lettenmaier X. Liang J.-F. Mahfouf J. Noilhan J. Polcher W. Qu A. Robock C. Rosenzweig C. A. Schlosser A. B. Shmakin J. Smith M. Suarez D. Verseghy P. Wetzel E. Wood Y. Xue 《Climate Dynamics》1999,15(9):673-684
Using atmospheric forcing data generated from a general circulation climate model, sixteen land surface schemes participating
in the Project for the Intercomparison of Land-surface Parametrization Schemes (PILPS) were run off-line to equilibrium using
forcing data from a GCM representative of a tropical forest and a mid-latitude grassland grid point. The values for each land
surface parameter (roughness length, minimum stomatal resistance, soil depth etc.) were provided. Results were quality controlled
and analyzed, focusing on the scatter simulated amongst the models. There were large differences in how the models’ partitioned
available energy between sensible and latent heat. Annually averaged, simulations for the tropical forest ranged by 79 1 3;W m-2 for the sensible heat flux and 80 W m-2 for the latent heat flux. For the grassland, simulations ranged by 34 W m-2 for the sensible heat flux and 27 W m-2 for the latent heat flux. Similarly large differences were found for simulated runoff and soil moisture and at the monthly
time scale. The models’ simulation of annually averaged effective radiative temperature varied with a range, between all the
models, of 1.4 K for tropical forest and 2.2 K for the grassland. The simulation of latent and sensible heat fluxes by a standard
‘bucket’ models was anomalous although this could be corrected by an additional resistance term. These results imply that
the current land surface models do not agree on the land surface climate when the atmospheric forcing and surface parameters
are prescribed. The nature of the experimental design, it being offline and with artificial forcing, generally precludes judgements
concerning the relative quality of any specific model. Although these results were produced de-coupled from a host model,
they do cast doubt on the reliability of land surface schemes. It is therefore a priority to resolve the disparity in the
simulations, understand the reasons behind the scatter and to determine whether this lack of agreement in de-coupled tests
is reproduced in coupled experiments.
Received: 15 October 1997 / Accepted: 22 April 1999 相似文献
4.
In different synoptic conditions and at different time scales,the analysis of the energy budgets by Bowen Ratio Method and Bulk Schemes over Huaihe River Basin during the field observation periods of HUBEX in 1999 shows that,(1) the averaged latent heat flux is an order of magnitude more than the averaged sensible heat flux during the observation period:(2) the variation of totalcloud amount is out of phase with the terms of energy budgets except for the downward longwave radiation which maybe is related to the cloud's height and class:(3) the values of sensible and latent heat fluxes are small during rain episodes,but thereafter,the values become high and then up to maximum.It is similar to the other terms of the energy budgets except for the downward longwave radiation.The diurnal variation of energy budgets indicates that the daytime precipitation exerts great influence to the energy budgets,but the nighttime precipitation makes little influence;(4) the variation of the latent heat flux is in phase with the evaporation,which indicates that the latent heat flux calculated by bulk schemes is reliable:(5) the means of the sensible and latent heat flux and momentum flux by bulk schemes for the time period from May to August are,respectively,30.71W/m2.116.81W/m2.2.86×10-2N/m2 in 1998 and 30.28W/m2,107.35W/m2,2.74×10-2N/m2 in 1999.The values of these two years are similar.During summer in 1999 the magnitude and activity of sensible heat flux are strongest in June and those of the latent heat flux are in August. 相似文献
5.
In this study, turbulent heat flux data from two sites within the Baltic Sea are compared with estimates from two models. The main focus is on the latent heat flux. The measuring sites are located on small islands close to the islands of Bornholm and Gotland. Both sites have a wide wind direction sector with undisturbed over-water fetch. Mean parameters and direct fluxes were measured on masts during May to December 1998.The two models used in this study are the regional-scale atmospheric model HIRLAM and the ocean model PROBE-Baltic. It is shown that both models overestimate the sensible and latent heat fluxes. The overestimation can, to a large extent, be explained by errors in the air-water temperature and humidity differences. From comparing observed and modelled data, the estimated 8-month mean errors in temperature and humidity are up to 1 °C and 1 g kg-1, respectively. The mean errors in the sensible and latent heat fluxes for the same period are approximately 15 and 30 W m-2, respectively.Bulk transfer coefficients used for calculating heat and humidity fluxes at the surface were shown to agree rather well with the measurements, at least for the unstable data. For stable stratification, the scatter in data is generally large, and it appears that the bulk formulation chosen overestimates turbulent heat fluxes. 相似文献
6.
The link between the sea-ice cover of the Amundsen Gulf and the overlying atmospheric boundary layer was explored on a weekly
timestep from winter to summer 2008. The total sea-ice cover was around 97% (3% leads) from 7 January to 21 April. From 28
April to 12 May, the total sea-ice cover approached 100%. From May 19, the total sea-ice declined rapidly to its July minimum
of 3%. During the winter, a turbulent internal boundary layer (IBL), attributed to the upward flux of sensible heat (mean = 46 W m−2), was present in most of the mean daily potential temperature profiles. The mean latent heat flux was 1.7 Wm−2. A turbulent IBL was also present in most of the mean daily profiles for early spring. Surface fluxes were not estimated.
During late spring and early summer, a stable IBL, attributed to the downward flux of sensible heat (mean = −19 W m−2), was present in most of the potential temperature profiles. Both downward and upward fluxes of latent heat occurred in this
period (means = −3.3 and 1.1 W m−2). The sensible heat flux estimates are consistent with the results of others; however, the latent heat flux estimates may
be too small due to condensation/deposition within the IBL. The unconsolidated nature of the pack ice in the Amundsen Gulf,
and the low sea-surface temperatures following break-up, were critical factors controlling the presence and type of IBL. 相似文献
7.
G. Pigeon A. Lemonsu C. S. B. Grimmond P. Durand O. Thouron V. Masson 《Boundary-Layer Meteorology》2007,124(2):269-290
This study quantifies the processes that take place in the layer between the mean building height and the measurement level
of an energy balance micrometeorological tower located in the dense old core of a coastal European city. The contributions
of storage, vertical advection, horizontal advection and radiative divergence for heat are evaluated with the available measurements
and with a three-dimensional, high-resolution meteorological simulation that had been evaluated against observations. The
study focused on a summer period characterized by sea-breeze flows that affect the city. In this specific configuration, it
appears that the horizontal advection is the dominant term. During the afternoon when the sea breeze is well established,
correction of the sensible heat flux with horizontal heat advection increases the measured sensible heat flux up to 100 W m−2. For latent heat flux, the horizontal moisture advection converted to equivalent latent heat flux suggests a decrease of
50 W m−2. The simulation reproduces well the temporal evolution and magnitude of these terms. 相似文献
8.
9.
Aircraft and ground-based measurements made during the1995 Australian OASIS field campaign are compared. The aircraft data were recorded during low-level flightsat 6 m above ground level and grid flights at altitudes of between 15 and 65 m, allin unstable atmospheric conditions. The low-level flights revealed an inadequate temperaturesensor response time, a correction for which was determined from subsequent work ina wind tunnel. Aircraft and ground-based measurements of mean wind speed, wind directionand air temperature agree to within 0.2 m s-1, 4° and 0.9 °C respectively.Comparisons between aircraft and ground-based observations of the standarddeviations of vertical velocity, horizontal wind speed, air temperature and specifichumidity have slopes of 0.96, 0.97, 0.92 and 0.99 respectively but the observed scatter isroughly twice the random error expected due to the averaging length of the aircraft data andthe averaging period of the ground-based data. For the low-level flights, the ground-basedand aircraft measurements of sensible and latent heat flux show mean differences of 27 and-25 W m-2 respectively, which reduce to 11 and -4 W m-2 respectivelywhen analysis of aircraft data is limited to areas immediately adjacent to the fluxtowers. For the flights at 15 to 65 m above ground level, the mean differences between theground-based and aircraft measurements of sensible and latent heat flux are -22 and-1 W m-2 respectively and these change to -1 and -7 W m-2 respectively oncethe effect of surface heterogeneity is included. Aircraft and ground-based measurementsof net radiation agree to within 6% at one ground-based site but differ by 20% at a second.Aircraft measurements of friction velocity at 6 m above the ground agree well withground-based data, but those from flights between 15 and 65 m above ground level do not.This is because at these heights the aircraft measurements provide the local shear stress,not the surface shear stress. Overall, the level of agreement allows confidence in the aircraftdata provided due care is taken of instrument response times and differences in thesurfaces sampled by aircraft and ground-based systems. 相似文献
10.
Bulk formulae for wind stress, sensible and latent heat flux are presented that are suitable for strong mesoscale events such as westerly wind bursts that contribute to the El Niño-Southern Oscillation (ENSO). Their exchange coefficients for heat and momentum have a simple polynomial dependence on wind speed and a linear dependence on air–sea temperature difference. The accuracy of these formulae are validated with respect to air–sea fluxes estimated using the standard algorithm adopted by the Tropical Ocean-Global AtmosphereCoupled-Ocean Atmosphere Response Experiment (TOGA COARE). The comparison ismade for observations from 96 Tropical Atmosphere Ocean (TAO) array and National Oceanographic Data Center (NODC) moorings in the equatorial and North Pacific Ocean spanning years 1990–1999. The bulk formulae are shown to have very small median root–mean-square differences with respect to the TOGA COARE estimates: 0.003 N m-2, 1.0 W m-2, and 10.0 W m-2 for the wind stress, sensible heat flux, and latent heat flux, respectively.The variability of air–sea fluxes during the 1997–1998 ENSO is also examined, along with a possible relationship between air–sea fluxes and surface ocean mixed layer depth (MLD). The wind stress and latent heat flux during the 1997 El Niño are found to be greater in the warm pool of the western Pacific than in the central Pacific where the ENSO is most clearly seen. These differences disappear upon the start of La Niña. The MLD in the equatorial Pacific is found to be moderately correlated to air–sea fluxes just before the start of the 1998 La Niña and poorly correlated otherwise. 相似文献
11.
Integrated Sensible Heat Flux Measurements of a Two-Surface Composite Landscape using Scintillometry 总被引：1，自引：0，他引：1
J.-P. Lagouarde J.-M. Bonnefond Y. H. Kerr K. J. McAneney M. Irvine 《Boundary-Layer Meteorology》2002,105(1):5-35
The potential of the LAS (large aperture scintillometry) method for measuring sensible heat flux (H) directly integrated over a two-field composite surface is evaluated. We describe a field experiment performed within the Alpilles/ReSeDa project in the south-east of France over a composite surface made up of wheat and bare soil (451 and 216 m long respectively) using two 0.15-m diameter scintillometers mounted at heights of 2.05 and 4.54 m. When compared against reference values obtained by the eddy correlation technique, LAS-measured sensible heat flux reveals a systematic overestimation of about 10%. A simple model describing the integration of the scintillometer signal along the beam for a two-field composite surface is described. A simulation of the experiment confirms that the bias observed isrelated to non-linearities in the integration process in relation with thebell-shape sensitivity curve of the instrument to the structure parameter for the refractive index it measures. The model is used to test the sensitivity of the LAS-derived H values to the composition of the pathlength (ratio of both surfaces) and to the contrast in sensible heat flux and roughness length between the two fields. Sensitivity tests to the aggregation scheme for roughness length (two of them are tested) and to the measurement height are also presented. The composition of the surface in combination with the contrast in sensible heat flux (in direct relation with the contrast in latent heat flux) explains most of the bias, with possible deviations ranging from -50 up to 80 W m-2. A tentative semi-empirical method for correcting the bias is suggested, which only requires a crude estimate of the contrast in component sensible heat fluxes along the pathlength. 相似文献
12.
以通用陆面模式CLM 3.0(Community Land Model 3.0)为模型算子,基于集合卡尔曼滤波(Ensemble Kalman Filter,En KF)发展了一个土壤温湿度同化系统,主要用于改进模式对土壤温湿度和地表水热通量的模拟精度,并考察集合样本数、同化频率及不同观测量的组合对同化效果的影响。该系统同化了FLUXNET两个站点(阿柔和Bondville)不同土壤深度、不同时间频率的土壤温度和湿度数据。通过对阿柔站不同集合样本数的设计,综合考虑计算成本和计算精度,最终将集合样本数设置为40。通过分析三种同化方案对同化频率的敏感性得出,同化土壤温度最为敏感,同时同化土壤温湿度次之,同化土壤湿度最不敏感。对于阿柔站点,同化系统对不同土壤深度温度和湿度的模拟精度均能提高90%,潜热通量的均方根误差由94.0 W·m~(-2)降为46.3 W·m~(-2),感热通量均方根误差由55.9 W·m~(-2)降为24.6 W·m~(-2)。Bondville站点浅层土壤温度的改进在30%左右,深层土壤温度改进达到60%,对土壤湿度的改进均在70%以上,潜热通量和感热通量的均方根误差分别从57.4 W·m~(-2)和54.4 W·m~(-2)降为51.0 W·m~(-2)和42.5 W·m~(-2)。试验结果表明,同化站点土壤温湿度数据对土壤水热状况及通量的模拟改进非常有效,同时也验证了同化土壤水分遥感产品的可行性和必要性。 相似文献
13.
Processing and quality control of flux data during LITFASS-2003 总被引：1，自引：0，他引：1
Matthias Mauder Claudia Liebethal Mathias Göckede Jens-Peter Leps Frank Beyrich Thomas Foken 《Boundary-Layer Meteorology》2006,121(1):67-88
Different aspects of the quality assurance and quality control (QA/QC) of micrometeorological measurements were combined to create a comprehensive algorithm which was then applied to experimental data from LITFASS-2003 (Lindenberg Inhomogeneous Terrain—Fluxes between Atmosphere and Surface: a long term Study). Eddy-covariance measurements of the latent heat flux were the main focus of the QA/QC efforts. The results of a turbulence sensor intercomparison experiment showed deviations between the different eddy-covariance systems on the order of 15%, or less than 30 W m−2, for the latent heat flux and 5%, or less than 10 W m−2, for the sensible heat flux. In order to avoid uncertainties due to the post-processing of turbulence data, a comprehensive software package was used for the analysis of experimental data from LITFASS-2003, including all necessary procedures for corrections and quality control. An overview of the quality test results shows that for most of the days more than 80% of the available latent heat flux data are of high quality so long as there are no instrumental problems. The representativeness of a flux value for the target land-use type was analysed using a stochastic footprint model. Different methods to calculate soil heat fluxes at the surface are discussed and a sensitivity analysis is conducted to select the most robust method for LITFASS-2003. The lack of energy balance closure, which was found for LITFASS-2003, can probably be attributed to the presence of low-frequency flux contributions that cannot be resolved with an averaging time of 30 min. Though the QA/QC system has been developed for the requirements of LITFASS-2003, it can also be applied to other experiments dealing with similar objectives. 相似文献
14.
With the aid of eddy correlation instrumentation, the components of the energy budget and CO2 flux were measured over grain sorghum grown at Mead, Nebraska. Diurnal patterns of sensible heat, latent heat, CO2 and momentum flux are examined for typical days. On a mostly clear day when the crop leaf area index was 3.7, net radiation reached a mid-day peak of 560 W m-2, while sensible and latent heat fluxes peaked at 50 and 460 W m-2, respectively. The peak CO2 flux occurring just prior to solar noon was 1.5 mg m-2(ground area) s-1. CO2 flux (respiration from plants, soil and roots) in the early evening was about -0.28 mg m-2 (ground area) s-1.A relationship between CO2 flux and photosynthetically active radiation (PAR) was developed. Except during the late stage of growth (growth stage 8.5, toward the initiation of senescence), the crop showed no evidence of saturation up to PAR 1800 Ei m-2s-1. The light compensation point was found to be about 211 Ei m-2s-1. Examination of CO2 flux-PAR relationships for selected days through the season indicated an aging effect in terms of a decrease in photosynthetic activity of the sorghum canopy. Measurements made on two consecutive days demonstrate the effects of weather conditions on CO2 flux and carbon-water flux ratio (a measure of water use efficiency of the crop). The occurrence of regional sensible heat advection with concommitant high vapor pressure deficit and air temperature-limited CO2 exchange reduced the carbon-water flux ratio.Published as Paper No. 7717, Journal Series, Nebraska Agricultural Research Division. The work was conducted under Regional Research Project 11-33 and Nebraska Agricultural Research Division Project 27-003.Formerly Post Doctoral Research Associate (now at the University of Connecticut Department of Renewable Natural Resources Storrs CT) 相似文献
15.
Increased heat fluxes near a forest edge 总被引：1，自引：0，他引：1
W. Klaassen P. B. van Breugel E. J. Moors J. P. Nieveen 《Theoretical and Applied Climatology》2002,72(3-4):231-243
Summary ?Observations of sensible and latent heat flux above forest downwind of a forest edge show these fluxes to be larger than
the available energy over the forest. The enhancement averages to 56 W m−2, or 16% of the net radiation, at fetches less than 400 m, equivalent to fetch to height ratios less than 15. The enhancement
of turbulent energy fluxes is explained by advection and increases with the difference in temperature and humidity of the
air over the upwind area as compared to the forest. The relatively high temperature and humidity of the upwind air are not
caused by high surface heat fluxes, but are explained by the relatively low aerodynamic roughness of the upwind surface. Although
the heat fluxes over forest are enhanced, the momentum fluxes are almost adjusted to the underlying forest. The different
behaviour of heat and momentum fluxes is explained by absorption of momentum by pressure gradients near the forest edge. It
is concluded that fetch requirements to obtain accurate surface fluxes from atmospheric observations need to be more stringent
for scalar fluxes as compared to momentum fluxes.
Received November 23, 2001; accepted May 13, 2002 相似文献
16.
The dependence of radiometric surface temperature (s) on view angle and the unclear definition of the aerodynamic temperature, which is the temperature that gives the correct sensible heat flux estimate at a specified roughness length, bring about a challenge in estimating sensible heat flux from s. An analytical-land-atmosphere-radiometer model (ALARM) has been developed to convert s taken at any zenith view angle to a clearly defined equivalent isothermal surface temperature, i, at a defined scalar roughness length. ALARM is an analytical model based on K-theory that links the foliage temperature profile to the radiometric surface temperature and the temperature felt by the turbulent lower atmosphere. ALARM has previously been applied with slightly different values of its parameters to several grassland sites of varying canopy density. Our objective in this study was to apply ALARM to these and to one additional dataset with a single parameterization. When compared to the reference (measured) values of sensible heat flux H, ALARM estimates of H had root mean square errors of about 35 W m-2. These results were comparable to those from two other simple canopy models also tested with these datasets. 相似文献
17.
D. Bala Subrahamanyam Radhika Ramachandran S. Indira Rani P. K. Kunhikrishnan B. Prasad Kumar 《Boundary-Layer Meteorology》2008,127(2):333-344
Surface-layer meteorological observations obtained from oceanic buoys over the Korean Strait and the Yellow Sea are used to
estimate surface-layer turbulent fluxes of heat, moisture and momentum over the East-Asian Marginal Seas. Special emphasis
is paid towards explanation of the impact of the Tsushima warm current flowing through the Korean Strait on air–sea interface
fluxes. During the active phase of the Tsushima warm current, when the difference in sea surface temperature and air temperature
becomes as large as 8°C, the sensible heat flux increases to a value of about 135 W m−2, while the latent heat flux is around 200 W m−2. The study attempts to broaden our understanding on the air-sea interaction processes over the Yellow Sea and Korean Strait. 相似文献
18.
Eddy correlation measurements of CO2, latent heat,and sensible heat fluxes over a crop surface 总被引：14，自引：0，他引：14
Eddy correlation equipment was used to measure mass and energy fluxes over a soybean crop. A rapid response CO2 sensor, a drag anemometer, a Lyman-alpha hygrometer and a fine wire thermocouple were used to sense the fluctuating quantities.Diurnal fluxes of sensible heat, latent heat and CO2 were calculated from these data. Energy budget closure was obtained by summing the sensible and latent heat fluxes determined by eddy correlation which balanced the sum of net radiation and soil heat flux. Peak daytime CO2 fluxes were near 1.0 mg m–2 (ground area) s–1.The eddy correlation technique was also employed in this study to measure nocturnal CO2 fluxes caused by respiration from plants, soil, and roots. These CO2 fluxes ranged from - 0.1 to - 0.25 mg m–2s–1.From the data collected over mature soybeans, a relationship between CO2 flux and photosynthetically active radiation (PAR) was developed. The crop did not appear to be light-saturated at PAR flux densities < 1800 Ei m–2 s–1. The light compensation point was found to be about 160 Ei m–2 s–1.Published as Paper No. 7402, Journal Series, Nebraska Agricultural Experiment Station. The work reported here was conducted under Nebraska Agricultural Experiment Station Project 27-003 and Regional Research Project 11–33.Post-doctoral Research Associate, Professor and Professor, respectively. Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, NE 68583-0728. 相似文献
19.
Abstract This study reports on testing of the peatland version of the Canadian Land Surface Scheme (CLASS) for simulating the energy balance of subarctic open woodland terrain. Model results are compared against several years of measured data from a site near Churchill, Manitoba. In contrast to most forest environments, the floor of the open forest plays a large role in total ecosystem energy exchange. This behaviour presents a significant challenge for land surface models like CLASS and their simplified treatment of vegetation canopies. Simulations of summer energy balance for seven years encompassing a wide range of meteorological conditions produced consistent results. Root mean square errors for sensible and latent heat fluxes fell between 11 and 28 W m?2. CLASS consistently underestimated slightly the daily latent heat flux and overestimated the sensible heat flux, average mean bias errors being ‐7.6 and 9.1 W m?2, respectively. The soil heat flux was less well represented. In general, CLASS was able to capture the diurnal and seasonal behaviour of the measured fluxes under a range of conditions with reasonable accuracy. In a full year simulation, CLASS reproduced the annual variations in energy balance with some discrepancies associated with snow accumulation and ablation periods. The model performance was sensitive to both snow density and specification of the surface cover. Recommendations for improving the model for subarctic woodlands and terrain types with similar features are discussed. 相似文献
20.
R. Milne 《Boundary-Layer Meteorology》1979,16(3):67-81
Transpiration of a 7 m-high Stika spruce forest was investigated using measurements of net radiation, sensible heat and ground
heat fluxes in an energy balance to give latent heat flux, and hence canopy resistance from the Penman-Monteith equation.
Sensible heat flux was measured by the eddy-correlation method using a Fluxatron circuit.
During six consecutive days of measurement in July/August, canopy resistance typically followed a decreasing trend from high
values (≈150 s m−1) at dawn to around 40 s m−1 at midday and then returning steadily to >100 s m−1 at sunset. Transpiration was 3 mm day−1 on average over the period studied and changes in the rate within the day were significantly correlated with changes in net
radiation.
Comparisons are drawn with published data from other forest sites and the conclusion is reached that it is imprudent to generalise
about transpiration rates and canopy resistances of different species at different sites from results gathered at one or two
places. 相似文献