Reciprocal Analysis of Sensible and Latent Heat Fluxes in a Forest Region Using Single Height Temperature and Humidity Based on the Bowen Ratio Concept

Evapotranspiration in forests has been researched for a long time because it serves an important role in water resource issues and biomass production. By applying the reciprocal analysis based on the Bowen ratio concept to the canopy surface, the sum result of sensible and latent heat fluxes, i.e., actual evapotranspiration (ET), is estimated from engineering aspect using the net radiation (Rn) and heat flux into the ground (G). The new method uses air temperature and humidity at a single height by determining the relative humidity (rehs) using the canopy temperature (Ts). The validity of the method is confirmed by the latent heat flux (lE) and sensible heat flux (H) observed by mean of eddy covariance method. The heat imbalance is corrected by multiple regression analysis. The temporal change of lE and H at the canopy surface is clarified using hourly and yearly data. Furthermore, the observed and estimated monthly evapotranspiration of the sites are compared. The research is conducted using hourly data and the validation of the method is conducted using observed covariance at five sites in the world using FLUXNET.