The relationship between the flux densities of sensible heat and water vapor and the mean specific concentration profile on the forest floor were examined in this study within a broad-leaved forest during the period of leaf shedding. Heat balance studies, including the energy storage term inside the litter on the forest floor were carried out and the results revealed the evaporation rates of water vapor from the litter into the atmosphere. On the forest floor, the measured sensible heat flux traveled upward and the temperature gradient indicated an upward transfer. The measured water vapor flux also traveled upward, whereas the humidity gradient indicated a downward transfer. The transfer of water vapor depicted a counter-gradient in the humidity profile within the trunk space.
In this study, the dry and wet bulb temperatures both inside of and on the surface of the litter were utilized for the lower level of the gradient profile to determine the difference in temperature and specific humidity between the two different heights.
Latent heat flux occupied less than 30% of the net radiation in May during periods without rainfall, except after rain events, when it occupied more than 100% of the received energy. Less than 2.0mm/day of water vapor were released after rainfall, and 0.5-0.8mm/day during the period without rainfall in May. 2.0mm/day were released after rainfall and less than 0.5mm/day during the periods without rainfall, occurring in November, in Hokkaido.
It is necessary to determine the bulk transfer coefficient for scalars and momentum in order to estimate the quantity transferred from the various surfaces. The bulk transfer coefficient for sensible heat was derived using both the eddy-correlation and gradient profile methods. The coefficient for water vapor was determined through a weighing device technique and the gradient profile method. The bulk transfer coefficient for sensible heat and water vapor on the forest floor was 10 to 50 times greater than that of the snow and ocean surfaces.