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000861110 1001_ $$0P:(DE-Juel1)129461$$aGraf, Alexander$$b0$$eCorresponding author
000861110 1112_ $$aEGU General Assembly$$cVienna$$d2019-04-07 - 2019-04-12$$wAustria
000861110 245__ $$aEnergy partitioning and water use efficiency anomalies 2018 at Eddy-Covariance sites across ecosystems
000861110 260__ $$c2019
000861110 300__ $$aEGU2019-5834-4
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000861110 520__ $$aDroughts 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 even a source forCO2, as expected from past studies on earlier events. The network density and number of site-years available now confirms that this was true for all major ecosystem types - forest, grassland and (rainfed) cropland, and resultedin increased atmospheric CO2 concentrations. However, notable exceptions occurred at elevated low mountain range sites and during early stages of the event, supporting the hypothesis of a balance between positive andnegative effects, where the former may prevail at strongly energy-limited sites with a usually large water surplus. H was mostly above-average, indicating that local heat production contributed to the event and was typically notsuppressed by warm air advection. LE as well as inferred GPP and R reacted most heterogeneously across sites, demonstrating the large discrepancy between potentially high fluxes due to high irradiation and temperature on theone hand, and suppression by water shortage on the other hand. Despite the variability in LE, its relation to NEE was such that ecosystem-level water use was less efficient than usual at the majority of sites through reduced CO2uptake.
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000861110 536__ $$0G:(DE-Juel1)BMBF-01LN1313A$$aIDAS-GHG - Instrumental and Data-driven Approaches to Source-Partitioning of Greenhouse Gas Fluxes: Comparison, Combination, Advancement (BMBF-01LN1313A)$$cBMBF-01LN1313A$$fNachwuchsgruppen Globaler Wandel 4+1$$x1
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000861110 536__ $$0G:(GEPRIS)15232683$$aDFG project 15232683 - TRR 32: Muster und Strukturen in Boden-Pflanzen-Atmosphären-Systemen: Erfassung, Modellierung und Datenassimilation (15232683)$$c15232683$$x3
000861110 7001_ $$0P:(DE-Juel1)159313$$aKlosterhalfen, Anne$$b1
000861110 7001_ $$0P:(DE-HGF)0$$aBernhofer, Christian$$b2
000861110 7001_ $$0P:(DE-HGF)0$$aBrümmer, Christian$$b3
000861110 7001_ $$0P:(DE-HGF)0$$aDrüe, Clemens$$b4
000861110 7001_ $$0P:(DE-HGF)0$$aGottschalk, Pia$$b5
000861110 7001_ $$0P:(DE-HGF)0$$aGrünwald, Thomas$$b6
000861110 7001_ $$0P:(DE-HGF)0$$aHeinemann, Günther$$b7
000861110 7001_ $$0P:(DE-HGF)0$$aHeinesch, Bernard$$b8
000861110 7001_ $$0P:(DE-HGF)0$$aKlatt, Janina$$b9
000861110 7001_ $$0P:(DE-HGF)0$$aKonopka, Jan$$b10
000861110 7001_ $$0P:(DE-HGF)0$$aDe Ligne, Anne$$b11
000861110 7001_ $$0P:(DE-HGF)0$$aLongdoz, Bernard$$b12
000861110 7001_ $$0P:(DE-HGF)0$$aMauder, Matthias$$b13
000861110 7001_ $$0P:(DE-Juel1)166467$$aNey, Patrizia$$b14
000861110 7001_ $$0P:(DE-HGF)0$$aRabbel, Inken$$b15
000861110 7001_ $$0P:(DE-HGF)0$$aRebmann, Corinna$$b16
000861110 7001_ $$0P:(DE-HGF)0$$aSachs, Torsten$$b17
000861110 7001_ $$0P:(DE-Juel1)144420$$aSchmidt, Marius$$b18
000861110 7001_ $$0P:(DE-HGF)0$$aSchrader, Frederik$$b19
000861110 7001_ $$0P:(DE-HGF)0$$aVincke, Caroline$$b20
000861110 7001_ $$0P:(DE-HGF)0$$aVölksch, Ingo$$b21
000861110 7001_ $$0P:(DE-HGF)0$$aWeber, Stephan$$b22
000861110 7001_ $$0P:(DE-HGF)0$$aWille, Christian$$b23
000861110 7001_ $$0P:(DE-Juel1)129549$$aVereecken, Harry$$b24
000861110 773__ $$0PERI:(DE-600)2144416-X$$tGeophysical research abstracts$$v21$$x1029-7006$$y2019
000861110 7870_ $$0FZJ-2019-01671$$aGraf, Alexander et.al.$$d2019$$iIsMemberOf$$r$$tEnergy partitioning and water use efficiency anomalies 2018 at Eddy-Covariance sites across ecosystems
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