Comments on ‘limitations of an Eddy-correlation technique for the determination of the carbon dioxide and sensible heat fluxes’

1975 ◽  
Vol 9 (3) ◽  
pp. 363-367 ◽  
Author(s):  
M. L. Wesely ◽  
B. B. Hicks
Keyword(s):  
Carbon Dioxide ◽  
Heat Fluxes ◽  
Eddy Correlation ◽  
Correlation Technique ◽  
Sensible Heat ◽  
Eddy Correlation Technique

scholarly journals Validation of Goudriaan's model: a case study for maize

1995 ◽  
Vol 43 (2) ◽  
pp. 163-181
Author(s):  
R.S. Singh ◽  
A.F.G. Jacobs
Keyword(s):  
Heat Flux ◽  
Soil Surface ◽  
Soil Heat Flux ◽  
Heat Fluxes ◽  
Eddy Correlation ◽  
Correlation Technique ◽  
Sensible Heat ◽  
Crop Canopy ◽  
Large Influence ◽  
Mean Square Errors

The crop microclimate model of Goudriaan was tested, using data collected in a maize field in the Netherlands during one day in summer 1986. Except for the soil heat flux, latent and sensible heat fluxes were simulated reasonably well. Goudriaan's model overestimated the latent and sensible heat fluxes above the crop canopy by 9 and 10%, respectively, in comparison with the eddy correlation technique. The simulated fluxes could be improved by a better incorporation of the effect of dewfall in the model. Root mean square errors of the simulated soil temperatures at 1, 5, 10 and 20 cm depth were between 0.30 and 0.68 K. Sensitivity analysis of the model showed that the heat fluxes were more sensitive to soil than to crop parameters, for the same magnitude of variations. Among soil parameters, the soil surface resistance to evaporation had a large influence on the latent heat and the sensible heat fluxes at the soil surface; it also influenced the soil heat flux. Soil water stress had a large influence on the daily net CO2 assimilation as well as the latent and the sensible heat fluxes above the crop canopy.

scholarly journals Low-level jets and above-canopy drainage as causes of turbulent exchange in the nocturnal boundary layer

2014 ◽  
Vol 11 (16) ◽  
pp. 4507-4519 ◽  
Author(s):  
T. S. El-Madany ◽  
H. F. Duarte ◽  
D. J. Durden ◽  
B. Paas ◽  
M. J. Deventer ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Wind Speed ◽  
Eddy Covariance ◽  
Latent Heat ◽  
Heat Fluxes ◽  
Vertical Wind ◽  
Sensible Heat ◽  
Intermittent Turbulence ◽  
Low Level Jets ◽  
Vertical Wind Velocity

Abstract. Sodar (SOund Detection And Ranging), eddy-covariance, and tower profile measurements of wind speed and carbon dioxide were performed during 17 consecutive nights in complex terrain in northern Taiwan. The scope of the study was to identify the causes for intermittent turbulence events and to analyze their importance in nocturnal atmosphere–biosphere exchange as quantified with eddy-covariance measurements. If intermittency occurs frequently at a measurement site, then this process needs to be quantified in order to achieve reliable values for ecosystem characteristics such as net ecosystem exchange or net primary production. Fourteen events of intermittent turbulence were identified and classified into above-canopy drainage flows (ACDFs) and low-level jets (LLJs) according to the height of the wind speed maximum. Intermittent turbulence periods lasted between 30 and 110 min. Towards the end of LLJ or ACDF events, positive vertical wind velocities and, in some cases, upslope flows occurred, counteracting the general flow regime at nighttime. The observations suggest that the LLJs and ACDFs penetrate deep into the cold air pool in the valley, where they experience strong buoyancy due to density differences, resulting in either upslope flows or upward vertical winds. Turbulence was found to be stronger and better developed during LLJs and ACDFs, with eddy-covariance data presenting higher quality. This was particularly indicated by spectral analysis of the vertical wind velocity and the steady-state test for the time series of the vertical wind velocity in combination with the horizontal wind component, the temperature, and carbon dioxide. Significantly higher fluxes of sensible heat, latent heat, and shear stress occurred during these periods. During LLJs and ACDFs, fluxes of sensible heat, latent heat, and CO2 were mostly one-directional. For example, exclusively negative sensible heat fluxes occurred while intermittent turbulence was present. Latent heat fluxes were mostly positive during LLJs and ACDFs, with a median value of 34 W m−2, while outside these periods the median was 2 W m−2. In conclusion, intermittent turbulence periods exhibit a strong impact on nocturnal energy and mass fluxes.

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