Hydrological Research Letters
Online ISSN : 1882-3416
ISSN-L : 1882-3416
Spatial variations in evapotranspiration over East Asian forest sites. I. Evapotranspiration and decoupling coefficient
Rehana KhatunTakeshi OhtaAyumi KotaniJun AsanumaMinoru GamoShijie HanTakashi HiranoYuichiro NakaiNobuko SaigusaKentaro TakagiHuimin WangNatsuko Yoshifuji
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Supplementary material

2011 Volume 5 Pages 83-87


Evapotranspiration (ET) is not only a vital component of water budget, but also plays an important role in the energy budget of the earth-atmospheric system, ultimately driving many regional and global scale climatological processes. This paper describes the ET characteristics and factors controlling ET across the 17 forest sites in East Asia (2°S to 64°N latitude). ET was measured using the eddy covariance technique at each site. Daytime dry-canopy data for the growing season were used in this study. Growing season mean ET gradually decreased as latitude increased, with a range of 4.4 to 1.2 mm d−1. The growing season mean decoupling coefficient (Ω) ranged from 0.42 to 0.11 across the studied sites. At low-latitude forest sites, Ω was close to 0.50, indicating that the bulk surface was partially decoupled from the atmosphere and ET was strongly controlled by net radiation and vapour pressure deficit. At high-latitude forest sites, Ω was low (∼0.12), indicating that the bulk surface was well coupled to the atmosphere and ET was mainly controlled by surface conductance. The value of Ω was determined mainly by the ratio of aerodynamic conductance to surface conductance across the studied forests of East Asia.

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© 2011 Japan Society of Hydrology and Water Resources
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