Abstract
The sum of the heat fluxes observed with the eddy covariance over a larch forest canopy in eastern Siberia is around 80% of the available energy. An analysis on the variation of the canopy conductance suggests that at least the latent heat flux is underestimated. The co-spectra of the fluctuations of temperature and humidity with the vertical wind velocity suggests that the contribution of the relatively large scale eddy (i.e., fluxes in the low frequency range) is evaluated insuffciently. Energy transportation including relatively large scale eddy is considered, and we define the advection flux as the product of the energy difference between incoming and outgoing air and the volume of advection air. We compute the flux assuming that the incoming air is above forest canopy and that the outgoing air is located at trunk space. The result shows that the advection volume is larger in the unstable condition than in stable atmospheric condition. Mean volume of the advection is 0.06m3m-2s-1. Mean diurnal change in the evaluated advection fluxes are positive in daytime and negative at night for the sensible heat, and always positive for the latent heat. Contribution of the advection flux to the sensible heat flux is 11%, and that to the latent heat flux is 54%. Finally, the total evapotranspiration during growing season is evaluated as 233mm. Thus the soil water extraction from the active layer is implied.
