Energy balance above a boreal coniferous forest: a difference in turbulent fluxes between snow-covered and snow-free canopies
✍ Scribed by Yuichiro Nakai; Tomoki Sakamoto; Tomomi Terajima; Kenzo Kitamura; Tomoki Shirai
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 391 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0885-6087
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✦ Synopsis
To evaluate the interactive eects of snow and forest on turbulent ¯uxes between the forest surface and the atmosphere, the surface energy balance above a forest was measured by the eddy correlation method during the winter of 1995±1996. The forest was a young coniferous plantation comprised of spruce and ®r. The study site, in Sapporo, northern Japan, had heavy and frequent snowfalls and the canopy was frequently covered with snow during the study period. A comparison of the observed energy balance above the forest for periods with and without a snow-covered canopy and an analysis using a single-source model gave the following results: during daytime when the canopy was covered with snow, the upward latent heat ¯ux was large, about 80% of the net radiation, and the sensible heat ¯ux was positive but small. On the other hand, during daytime when the canopy was dry and free from snow, the sensible heat ¯ux was dominant and the latent heat ¯ux was minor, about 10% of the net radiation. To explain this dierence of energy partition between snow-covered and snowfree conditions, not only dierences in temperature but also dierences in the bulk transfer coecients for latent heat ¯ux were necessary in the model. Therefore, the high evaporation rate from the snow-covered canopy can be attributed largely to the high moisture availability of the canopy surface. Evaporation from the forest during a 60-day period in midwinter was estimated on a daily basis as net radiation minus sensible heat ¯ux. The overall average evaporation during the 60-day period was 0 . 6 mm day À1 , which is larger than that from open snow ®elds.