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Comparison of eddy covariance and bowen ratio energy balance method. Energy balance cloruse versus bowen ratio similarity assumption
Fischer, Milan ; Trnka, Miroslav ; Pozníková, Gabriela ; Sedlák, Pavel ; Orság, Matěj ; Kučera, J. ; Žalud, Z.
The Bowen ratio and the Monin-Obukhov similarity principles are based on the assumption that the eddy diff usivities for temperature and humidity are equal to each other under all atmospheric stratifi cations within turbulent surface boundary layer. However, several authors reported that this equality was violated under advective inversion or during the non-stationary conditions due to clouds passing by and sudden change of wind speed and direction. Th e inequality of the eddy diff usivity can lead to errors in the energy partitioning estimates by gradient techniques like the Bowen ratio energy balance (BREB) and the aerodynamical method, or methods based on residual energy balance such as the Penman-Monteith or Priestley-Taylor models. Th is study investigates two seasons of simultaneous measurement by eddy covariance (EC) and BREB above a high density poplar plantation at the Domanínek locality. Th e direct measurement of eddy diff usivities by EC is reinvestigating the validity of the long term measurement (since 2008) by BREB. Results showed unequal exchange coeffi cients with their mean 0.31 to 0.35 m2 s-1 for 2011 and 2012, respectively, favouring the transport of latent heat. Th is might be explained by the diff erent footprints of the BREB and EC methods, an undeveloped internal boundary layer or instrumental errors.
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