Differences in the Characteristics of the Heat Balance
above the Canopies of Evergreen Forest
and Deciduous Forest while Snow Covered
Takeshi Ohta1, Kazuyoshi Suzuki1, Yuji Kodama2, Jumpei Kubota3,
Yuji Kominami4, and Yuichiro Nakai5
Heat and water exchanges in forest areas constitute one of the most important hydrometeorological
systems. A lot of investigations about the heat and water exchanges were carried out on the snow-
free forest canopy compared with on the snow-covered canopy. Unfortunately, therefore, little is
known about the characteristics of energy balances in forest areas when covered by snow.
In the present study, the energy balances above three forests located in northern Japan were mea-
sured when the land surface was covered with snow. Two were evergreen conifer forests and the
third was deciduous. The characteristics of the heat balance are investigated above each forest
canopy during the snow-covered season, and the properties of the aerodynamic parameters are
discussed in this paper.
From this study we obtained the following new interpretations: There was no significant distinc-
tion between the magnitudes of net radiation and sensible heat, and the ratio of sensible heat to net
radiation among the three experimental forests, despite the major differences in canopy conditions.
Net short-wave radiation was larger above the evergreen forests than above the deciduous forest.
However, for net long-wave radiation, the converse was true; this may be due to the difference in
the upward long-wave radiation. Consequently, there was no clear distinction between the net all-
wave radiation above the two types of canopy. Canopy conditions caused major differences in
roughness length and zero plan displacement. In the deciduous forest, the zero plan displacement
was small and roughness length was large, while in the evergreen forest the opposite was true. In
the deciduous forest, the area in contact with the atmosphere increased because of the low position
of the "active surface," and roughness length was also high. Consequently, sensible heat from the
deciduous forest did not differ from that of the evergreen forests.
1
Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan
2
Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
3
Faculty of Agriculture, Tokyo University of Agriculture and Technology, Futyu 183-8509, Japan
4
Kansai Research Center, Forestry and Forest Products Research Center, Kyoto 612-0865, Japan
5
Hokkaido Research Center, Forestry and Forest Products Research Center, Sapporo 062-0045, Japan
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