Energy partitioning and water use efficiency anomalies 2018 at Eddy-Covariance sites across ecosystems

Medientyp: Elektronischer Konferenzbericht

Titel: Energy partitioning and water use efficiency anomalies 2018 at Eddy-Covariance sites across ecosystems

Beteiligte: Graf, Alexander [Verfasser:in]; Klosterhalfen, Anne [Verfasser:in]; Konopka, Jan [Verfasser:in]; De Ligne, Anne [Verfasser:in]; Longdoz, Bernard [Verfasser:in]; Mauder, Matthias [Verfasser:in]; Ney, Patrizia [Verfasser:in]; Rabbel, Inken [Verfasser:in]; Rebmann, Corinna [Verfasser:in]; Sachs, Torsten [Verfasser:in]; Schmidt, Marius [Verfasser:in]; Schrader, Frederik [Verfasser:in]; Bernhofer, Christian [Verfasser:in]; Vincke, Caroline [Verfasser:in]; Völksch, Ingo [Verfasser:in]; Weber, Stephan [Verfasser:in]; Wille, Christian [Verfasser:in]; Vereecken, Harry [Verfasser:in]; Brümmer, Christian [Verfasser:in]; Drüe, Clemens [Verfasser:in]; Gottschalk, Pia [Verfasser:in]; Grünwald, Thomas [Verfasser:in]; Heinemann, Günther [Verfasser:in]; Heinesch, Bernard [Verfasser:in];

Erschienen: Forschungszentrum Jülich: JuSER (Juelich Shared Electronic Resources), 2019

Sprache: Englisch

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Beschreibung: Droughts and heat waves deeply interact with the exchange of energy and matter between land surface and atmosphere. The conditions associated with a combined heat wave and drought can have positive or negative effects on the sensible heat flux (H), latent heat flux (LE), and net flux of CO2 (NEE). In return, while each of these fluxes can exert different local feedbacks on temperature, atmospheric humidity and soil moisture, all of them result in bulk heating of the troposphere (H and LE through direct local and indirect non-local heat transfer, and NEE through radiative forcing). H is positively affected by increased solar irradiation, but can be supressed by advection of warm air diminishing the gradient between surface and air temperature. Potential LE is positively affected by irradiation, temperature and water vapour pressure deficit, but actual LE can be suppressed by stomatal closure of plants and by reduced soil moisture from low rainfall and high past LE. NEE is the result of plant photosynthesis (GPP) and plant and soil respiration (R), both of which can be enhanced by high temperatures or irradiation, and suppressed by drought. Focusing on direct measurements mostly by a network of Eddy-Covariance (EC) stations of the ICOS (www.icosri.eu), TERENO (www.tereno.net) and other networks, we hypothesize that the net effect of the 2018 event at a site, and thus its feedback on global warming, depends on the balance between co-existing positive and negative effects of the combined heat wave and drought on the respective fluxes. Variables such as albedo, growing degreedays (GDD), soil moisture and ecosystem-level water use efficiency help to separate these co-existing positive and negative effects from each other. Preliminary results indicate different degrees of heterogeneity between sites fordifferent variables. As expected, reduced precipitation and soil moisture, as well as increased GDD, could be found at almost all sites in the affected region. NEE was mostly less negative, indicating a weaker sink or ...

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