Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites

Medientyp: E-Artikel
Titel: Energy partitioning between latent and sensible heat flux during the warm season at FLUXNET sites
Beteiligte: Wilson, Kell B.; Baldocchi, Dennis D.; Aubinet, Marc; Berbigier, Paul; Bernhofer, Christian; Dolman, Han; Falge, Eva; Field, Chris; Goldstein, Allen; Granier, Andre; Grelle, Achim; Halldor, Thorgeirsson; Hollinger, Dave; Katul, Gabriel; Law, B. E.; Lindroth, Anders; Meyers, Tilden; Moncrieff, John; Monson, Russ; Oechel, Walter; Tenhunen, John; Valentini, Riccardo; Verma, Shashi; Vesala, Timo;
Erschienen: American Geophysical Union (AGU), 2002
Erschienen in: Water Resources Research
Sprache: Englisch
DOI: 10.1029/2001wr000989
ISSN: 0043-1397; 1944-7973
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Beschreibung: <jats:p>The warm season (mid‐June through late August) partitioning between sensible (<jats:italic>H</jats:italic>) and latent (<jats:italic>LE</jats:italic>) heat flux, or the Bowen ratio (β = <jats:italic>H</jats:italic>/<jats:italic>LE</jats:italic>), was investigated at 27 sites over 66 site years within the international network of eddy covariance sites (FLUXNET). Variability in β across ecosystems and climates was analyzed by quantifying general climatic and surface characteristics that control flux partitioning. The climatic control on β was quantified using the climatological resistance (<jats:italic>R</jats:italic><jats:sub><jats:italic>i</jats:italic></jats:sub>), which is proportional to the ratio of vapor pressure deficit (difference between saturation vapor pressure and atmospheric vapor pressure) to net radiation (large values of <jats:italic>R</jats:italic><jats:sub><jats:italic>i</jats:italic></jats:sub> decrease β). The control of flux partitioning by the vegetation and underlying surface was quantified by computing the surface resistance to water vapor transport (<jats:italic>R</jats:italic><jats:sub><jats:italic>c</jats:italic></jats:sub>, with large values tending to increase β). There was a considerable range in flux partitioning characteristics (<jats:italic>R</jats:italic><jats:sub><jats:italic>c</jats:italic></jats:sub>, <jats:italic>R</jats:italic><jats:sub><jats:italic>i</jats:italic></jats:sub> and β) among sites, but it was possible to define some general differences between vegetation types and climates. Deciduous forest sites and the agricultural site had the lowest values of <jats:italic>R</jats:italic><jats:sub><jats:italic>c</jats:italic></jats:sub> and β (0.25–0.50). Coniferous forests typically had a larger <jats:italic>R</jats:italic><jats:sub><jats:italic>c</jats:italic></jats:sub> and higher β (typically between 0.50 and 1.00 but also much larger). However, there was notable variability in <jats:italic>R</jats:italic><jats:sub><jats:italic>c</jats:italic></jats:sub> and <jats:italic>R</jats:italic><jats:sub><jats:italic>i</jats:italic></jats:sub> between coniferous site years, most notably differences between oceanic and continental climates and sites with a distinct dry summer season (Mediterranean climate). Sites with Mediterranean climates generally had the highest net radiation, <jats:italic>R</jats:italic><jats:sub><jats:italic>c</jats:italic></jats:sub>, <jats:italic>R</jats:italic><jats:sub><jats:italic>i</jats:italic></jats:sub>, and β. There was considerable variability in β between grassland site years, primarily the result of interannual differences in soil water content and <jats:italic>R</jats:italic><jats:sub><jats:italic>c</jats:italic></jats:sub>.</jats:p>
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