Eddy-covariance measurement of energy and substances fluxes
Eddy-covariance system is measuring fluxes of energy (sensible and latent heat, momentum flux) and substances (carbon dioxide, water vapour) between the homogeneous or non-homogeneous surfaces and the atmosphere. In EESS Bílý Kříž it is situated above the young spruce stand and above the grassland.
Eddy-covarinace system on the meteorological tower above the young spruce stand.
Main system components
Ultrasonic anemometer: It measures the wind speed in all three components of its vector, wind direction and virtual ultrasonic temperature. It is working on the principle of ultrasonic pulses rate transfer in the measuring frequency of 21 Hz.
Utrasonic anemometer.
Infrared gas analyser: It measures instantaneous air concentration of CO2 and H2O. The values are sent back to the anemometr, transferred from analog to digital and together with the windspeed and wind direction data forwarded to the computer processing.
Infrared gas analyser is located on the tower.
Software calculates energy and substances fluxes by the eddy-covariace method. Covariance is calculated from the confluent measurement of velocity and scalar quantities (substance concentration, temperature) of individual air eddies.
Control unit of the system is placed/located under the tower
Examples of energy and substances fluxes
Figure 1. Fluxes of sensible and latent heat and global radiation in the sunny day. During the white day, the heat is emitted from stand to the atmosphere in relation to the energy delivered by solar radiation.
Figure 2. Fluxes of carbon dioxide (CO2) between the stand and the atmosphere. During the white day, the curve denotes the difference between assimilation and respiration, during the night it denotes the respiration of the stand. Negative values indicate uptake of CO2 by the stand,
positive values its emission to the atmospere.
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