Bowen Ratio Energy Balance (BREB) system is in principle a meterological station completed with one more air temperature/humidity sensor and with net radiation sensor. It is based on the theory of turbulent diffusion with all its limits. However, if the user is aware of those limits, the BREB system gives useful results of real evapotranspiration incomparably cheaper than sophisticated eddy covariance equipment. The real arrangement depends on the height of the canopy and the available budget. When measuring on higher canopies we recommend installing temperature /humidity sensors in three levels for more reliable data:
ET and Bowen ratio calculated from sensors at three levels.
Note the increase of Bowen ratio followed by downtrend of evapotranspiration in the afternoon.