Influence of canopy snow on water and energy balances above and below the canopy of a coniferous plantation in northern Japan

Evaporation of snow intercepted by the forest canopy is an important component of the water and energy balances in forests seasonally covered with snow. Knowledge of the snow interception and evaporation processes in forest canopies is important for our understanding of the water cycle in forested areas. In the present study, we examined the influence of canopy snow on water and energy balances above a coniferous forest in the Hitsujigaoka Experimental Forest of Japan during winter 1997 1998. Measured data comprised eddy covariance fluxes above the forest, micrometeorological data, and canopy snow monitoring data obtained from photographs and by weighing a cut tree. The maximum canopy snow storage was around 6.9 mm water equivalent. As the proportion of snow-covered area to the total canopy projected area increased, the Bowen ratio decreased significantly above the forest canopy. Sensible heat flux was proportional to the areal proportion of snow on the canopy and was positively correlated with the Bowen ratio. The quantity of canopy snow strongly influenced the latent and sensible heat fluxes above the canopy. Snow interception by forest canopy was about 26 % of the accumulated snowfall from 1 January 1998 to 31 March 1998.