Study on water and heat cycle in forest areas with snow cover

1996年2月和1997年2月在一片落叶白蜡林进行了密集观测。通过这些观测得到的结果与在常绿森林中得到的结果进行了比较。以下是对本研究的新解读。(1)白蜡林的净辐射和感热与常绿林相似，但冠层条件有明显差异。(2)白蜡林的向上长波辐射小于常绿林，从而抵消了三种森林之间的反照率差异。因此，净辐射没有显著差异。(3)白蜡林的零面位移很小，大部分林冠层与大气的热交换是有效的。此外，白蜡林的粗糙度长度大于常绿林，加速了混交。这可能是感热相似的一个原因。关于冠层截留，得到了一些新的解释。以下是在北海道获得的结果。(1)2月份的蒸发量大于融化季节，这是因为树冠的积雪时间较长。(2)日平均值为0.8 mm/d，是开阔地的两倍。在托卡马奇镇取得的其他结果，那里是一个更温暖和多雪的地区。(1)平均截留率为2.7~4.2 mm/d。这一比率是净辐射的两倍。(2)林地与开阔地雪当量的差异主要是由积雪截留引起的。

The intensive observations were carried out in February 1996 and 1997 at a ash tree forest which was deciduous. The results obtained by these observations were compared to those gotten at evergreen forests. The followings are the new interpretation by this study. (1) Net radiation and sensible heat on the ash tree forest were similar to those on the evergreen forests though there were clear distinctions about canopy conditions. (2) Upward long-wave radiation at the was smaller at the ash tree forest than at the evergreen forest, so differences of albedo among the three forest were set off. Consequently, there was no remarkable difference on net radiation. (3) Zero plane displacement in the ash tree forest was very low and a large part of the canopy layr was effective for heat exchange with atmosphere. Moreover, roughness length was higher at the ash tree forest than at the evergreen forests, so mixing was accelerated. This might be a reason for the fact that sensible heat was similar to each other.About interception on canopies, some new interpretaions were gotten. The followings are the results obtained in Hokkaido. (1) Evaporation was larger in February than during a melting season, because a snow covered period of a canopy was longer. (2) The daily mean values was 0.8 mm/day, and this is twice as large as the values was obtained at an open area. Other results obtained in Tokamachi town where was a warmer and snowy region. (1) The mean interception rate was 2.7-4.2 mm/day. This rate was twice as large as net radiation was. (2) Differences of water equivalent of snow between at a forest and at an open site were mainly caused by snow interception.