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	Energy budget above a temperate mixed forest in northeastern China
	Wu J. B. ; Guan D. X. ; Han S. J. ; Shi T. L. ; Jin C. J. ; Pell T. F. ; Yu G. R.
	2007
关键词	energy budget sensible heat flux latent heat flux eddy covariance technique temperate forest carbon-dioxide exchange water-vapor flux measurements deciduous forest seasonal-variation boreal forest larch forest heat-flux long-term balance
英文摘要	Components of the energy budget were measured continuously above a 300-year-old temperate mixed forest at the Changbaishan site, northeastern China, from I January to 31 December 2003, as a part of the ChinaFlux programme. The albedo values above the canopy were lower than most temperate forests, and the values for snow-covered canopy were over 50% higher than for the snow-free canopy. In winter, net radiation R-n was generally less than 5% of the summer value due to high albedo and low incoming solar radiation. The annual mean latent heat LE was 37.5 W m(-2), accounting for 52% of Rn. The maximum daily evaporation was about 4.6 mat day(-1) in summer. Over the year, the accumulated precipitation was 578 mm; this compares with 493 mm of evapotranspiration, which shows that more than 85% of water was returned to the atmosphere through evapotranspiration. The LE was strongly affected by the transpiration activity and increased quickly as the broadleaved trees began to foliate. The sensible heat H dropped at that time, although Rn increased. Consequently, the seasonal variation in the Bowen ratio was clearly U-shaped, and the minimum value (0-1) occurred on a sunny day just after rain, when most of the available energy was used for evapotranspiration. Negative beta values occurred occasionally in the non-growing season as a result of intensive radiative cooling and the presence of water on the surface. The was very high (up to 13-0) in snow-covered winter, when evapotranspiration was small due to low surface temperature and available soil water. Vegetation phenology and soil moisture were the key variables controlling the available energy partitioning between H and LE. Energy budget closure averaged better than 86% on a half-hourly basis, with slightly greater closure on a daily basis. The degree of closure showed a dependence on friction velocity u*. Copyright (C) 2006 John Wiley & Sons, Ltd.
出处	Hydrological Processes
卷	21
期	18
页	2425-2434
收录类别	SCI
语种	英语
ISSN号	0885-6087
内容类型	SCI/SSCI论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/22793]
专题	地理科学与资源研究所_历年回溯文献
推荐引用方式 GB/T 7714	Wu J. B.,Guan D. X.,Han S. J.,et al. Energy budget above a temperate mixed forest in northeastern China. 2007.

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