You are standing in front of the extraordinary Eddy Covariance weather station. Ordinary weather stations measure many meteorological quantities: air temperature profile, air pressure, atmospheric precipitation, air velocity and direction, solar radiation, heat flux to the soil, soil temperature and soil moisture.
What does Eddy Covariance do in addition?
You are looking at the degree of correlation (covariance) between the concentration of water vapour and carbon dioxide with turbulent air flow at the atmospheric border layer. You can think of turbulent flows as small eddies. These eddies are measured using a 3D ultrasonic anemometer (measures wind direction and speed) with subsequent extraction of the vertical component of the wind. The concentrations of the gases are measured by optical spectrometry, during which air is drawn as close as possible to the anemometer into the spectrometer to determine the concentrations of these gases. It is this suction process that causes the distinct whistling of the station that you have probably noticed. The station records data about the concentration and velocity of the gases ten times per second. It processes the other data at half-hourly intervals. From this data we calculate the actual evapotranspiration of water into the atmosphere around the station. This is the water that evaporates from the surface and is exhaled by plants. The Eddy Covariance station is currently monitoring the condition of the area prior to the planned construction of a small reservoir. By recording data now, we will be able to determine the impact of the reservoir on the local microclimate in the future.
