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52. Controls on winter ecosystem respiration in temperate and boreal ecosystems

Author

J. W. Munger, Barbara Marcolla, D.Y. Hollinger, Fabienne Maignan, Tao Wang, Christopher M. Gough, Hank A. Margolis, Charles D. Koven, Peter M. Lafleur, Andrew E. Suyker, Russell K. Monson, Eddy Moors, Timo Vesala, S. L. Piao, Andy Black, Altaf Arain, Leonardo Montagnani, Lianhong Gu, Damiano Gianelle, P. Brender, Georg Wohlfahrt, Andrej Varlagin, Alexander Knohl, Axel Don, Catherine Ottlé, A. Cescatti, Terhi K. Laurila, P. Ciais, Shashi B. Verma, Ebba Dellwik, Nobuko Saigusa, Department of Physics, Ecosystem processes (INAR Forest Sciences), Micrometeorology and biogeochemical cycles, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), ICOS-ATC (ICOS-ATC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), College of Urban and Environmental Sciences [Beijing], Peking University [Beijing], Modélisation des Surfaces et Interfaces Continentales (MOSAIC), McMaster University [Hamilton, Ontario], Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
sub-alpine forest, 010504 meteorology & atmospheric sciences, lcsh:Life, NORTHERN WISCONSIN, Eddy covariance, Atmospheric sciences, soil respiration, 01 natural sciences, Soil respiration, Global winter respiration, HARDWOOD FOREST, CWK - Earth System Science and Climate Change, Wageningen Environmental Research, VEGETATION TYPES, ComputingMilieux_MISCELLANEOUS, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Ecology, CARBON-DIOXIDE EXCHANGE, lcsh:QE1-996.5, deciduous forest, 04 agricultural and veterinary sciences, PE&RC, Fluxnet, NET ECOSYSTEM, hardwood forest, Ecosystem respiration, winter ecosystem respiration, boreal, ecosystems, INTERANNUAL VARIABILITY, SOIL RESPIRATION, northern wisconsin, SUB-ALPINE FOREST, interannual variability, education, 114 Physical sciences, Carbon cycle, lcsh:QH540-549.5, Forest ecology, Temperate climate, Ecosystem, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, 1172 Environmental sciences, 0105 earth and related environmental sciences, Earth-Surface Processes, carbon-dioxide exchange, net ecosystem, atmosphere co2 exchange, WIMEK, vegetation types, 15. Life on land, Evergreen, CWC - Earth System Science and Climate Change, DECIDUOUS FOREST, lcsh:Geology, lcsh:QH501-531, 13. Climate action, Wildlife Ecology and Conservation, ATMOSPHERE CO2 EXCHANGE, 040103 agronomy & agriculture, 0401 agriculture, forestry, and fisheries, Environmental science, lcsh:Ecology
Abstract

Winter CO2 fluxes represent an important component of the annual carbon budget in northern ecosystems. Understanding winter respiration processes and their responses to climate change is also central to our ability to assess terrestrial carbon cycle and climate feedbacks in the future. However, the factors influencing the spatial and temporal patterns of winter ecosystem respiration (Reco) of northern ecosystems are poorly understood. For this reason, we analyzed eddy covariance flux data from 57 ecosystem sites ranging from 35 N to 70 N. Deciduous forests were characterized by the highest winter Reco rates (0.90±0.39 gCm−2 d−1), when winter is defined as the period during which daily air temperature remains below 0 C. By contrast, arctic wetlands had the lowest winter Reco rates (0.02±0.02 gCm−2 d−1). Mixed forests, evergreen needle-leaved forests, grasslands, croplands and boreal wetlands were characterized by intermediate winter Reco rates (g Cm−2 d−1) of 0.7 (±0.33), 0.60(±0.38), 0.62(±0.43), 0.49(±0.22) and 0.27(±0.08), respectively. Our cross site analysis showed that winter air (Tair) and soil (Tsoil) temperature played a dominating role in determining the spatial patterns of winter Reco in both forest and managed ecosystems (grasslands and croplands). Besides temperature, the seasonal amplitude of the leaf area index (LAI), inferred from satellite observation, or growing season gross primary productivity, which we use here as a proxy for the amount of recent carbon available for Reco in the subsequent winter, played a marginal role in winter CO2 emissions from forest ecosystems. We found that winter Reco sensitivity to temperature variation across space (QS) was higher than the one over time (interannual, QT ). This can be expected because QS not only accounts for climate gradients across sites but also for (positively correlated) the spatial variability of substrate quantity. Thus, if the models estimate future warming impacts on Reco based onQS rather thanQT, this could overestimate the impact of temperature changes., JRC.H.7-Climate Risk Management

Published
2011
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53. Flow tilt angle measurements from the ground

Author

Jakob Mann, Ebba Dellwik, Ferhat Bingöl, Michael Courtney, and Dimitri Foussekis

Subjects
Wind power meteorology, Vindenergi, Wind energy, Vindkraftmeteorologi
Published
2010

54. Contrasting response of European forest and grassland energy exchange to heatwaves

Author

Reto Stöckli, Damiano Gianelle, Bart van den Hurk, Leonardo Montagnani, Adriaan J. Teuling, Matteo Sottocornola, Katja Klumpp, Bert Gielen, Philippe Ciais, Markus Reichstein, Christian Bernhofer, Christof Ammann, Sebastiaan Luyssaert, Sonia I. Seneviratne, Thomas Grünwald, Georg Wohlfahrt, Christine Moureaux, Eddy Moors, Ebba Dellwik, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Hydrology and Quantitative Water Management Group, Wageningen University and Research [Wageningen] (WUR), Federal Office of Meteorology and Climatology, Partenaires INRAE, Max Planck Institute for Biogeochemistry (MPI-BGC), Max-Planck-Gesellschaft, Wageningen University and Research Centre (WUR), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), ICOS-ATC (ICOS-ATC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), KNMI, Agroscope, Institute of Hydrology and Meteorology [Dresden], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Risø National Laboratory for Sustainable Energy (Risø DTU), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Istituto Agrario di San Michele all'Adige (IASMA), Department of Biology, University of Antwerp (UA), Unité de recherche sur l'Ecosystème Prairial (UREP), Institut National de la Recherche Agronomique (INRA), Forest Services, Free University of Bozen-Bolzano, Gembloux Agro-BioTech, Université de Liège, Institute of Ecology, Leopold Franzens Universität Innsbruck - University of Innsbruck, Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Technical University of Denmark [Lyngby] (DTU), UR 0874 Unité de recherche sur l'Ecosystème Prairial, Institut National de la Recherche Agronomique (INRA)-Unité de recherche sur l'Ecosystème Prairial (UREP)-Ecologie des Forêts, Prairies et milieux Aquatiques (EFPA), University of Innsbruck, Earth and Climate, Systems Ecology, and Spatial analysis & Decision Support

Subjects
summer, 010504 meteorology & atmospheric sciences, [SDV]Life Sciences [q-bio], water-vapor, 0207 environmental engineering, anemometer (co)sine response, Climate change, balance closure, 02 engineering and technology, Land cover, flux measurements, Hydrology and Quantitative Water Management, 01 natural sciences, transpiration, Atmosphere, Deforestation, deforestation, CWK - Earth System Science and Climate Change, Wageningen Environmental Research, 020701 environmental engineering, Water content, Biology, 0105 earth and related environmental sciences, Transpiration, WIMEK, Global warming, 15. Life on land, CWC - Earth System Science and Climate Change, 13. Climate action, Climatology, climate-change, impact, General Earth and Planetary Sciences, Environmental science, heat-wave, Water use, Hydrologie en Kwantitatief Waterbeheer
Abstract

International audience; Recent European heatwaves have raised interest in the impact of land cover conditions on temperature extremes. At present, it is believed that such extremes are enhanced by stronger surface heating of the atmosphere, when soil moisture content is below average. However, the impact of land cover on the exchange of water and energy and the interaction of this exchange with the soil water balance during heatwaves is largely unknown. Here we analyse observations from an extensive network of flux towers in Europe that reveal a difference between the temporal responses of forest and grassland ecosystems during heatwaves. We find that initially, surface heating is twice as high over forest than over grassland. Over grass, heating is suppressed by increased evaporation in response to increased solar radiation and temperature. Ultimately, however, this process accelerates soil moisture depletion and induces a critical shift in the regional climate system that leads to increased heating. We propose that this mechanism may explain the extreme temperatures in August 2003. We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates the impact of the most extreme heat and/or long-lasting events.

Published
2010
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55. Flow tilt angles near forest edges - Part 2: Lidar anemometry

Author

Ferhat Bingöl, Jakob Mann, and Ebba Dellwik

Subjects
lcsh:QE1-996.5, lcsh:Life, Terrain, Conical surface, Vindenergi, Wind speed, lcsh:Geology, symbols.namesake, lcsh:QH501-531, Lidar, Anemometer, lcsh:QH540-549.5, symbols, Vector field, Mean flow, lcsh:Ecology, Wind power meteorology, Doppler effect, Wind energy, Ecology, Evolution, Behavior and Systematics, Geology, Physics::Atmospheric and Oceanic Physics, Earth-Surface Processes, Remote sensing, Vindkraftmeteorologi
Abstract

A novel way of estimating near-surface mean flow tilt angles from ground based Doppler lidar measurements is presented. The results are compared with traditional mast based in-situ sonic anemometry. The tilt angle assessed with the lidar is based on 10 or 30 min mean values of the velocity field from a conically scanning lidar. In this mode of measurement, the lidar beam is rotated in a circle by a prism with a fixed angle to the vertical at varying focus distances. By fitting a trigonometric function to the scans, the mean vertical velocity can be estimated. Lidar measurements from (1) a fetch-limited beech forest site taken at 48–175 m a.g.l. (above ground level), (2) a reference site in flat agricultural terrain and (3) a second reference site in complex terrain are presented. The method to derive flow tilt angles and mean vertical velocities from lidar has several advantages compared to sonic anemometry; there is no flow distortion caused by the instrument itself, there are no temperature effects and the instrument misalignment can be corrected for by assuming zero tilt angle at high altitudes. Contrary to mast-based instruments, the lidar measures the wind field with the exact same alignment error at a multitude of heights. Disadvantages with estimating vertical velocities from a lidar compared to mast-based measurements are potentially slightly increased levels of statistical errors due to limited sampling time, because the sampling is disjunct, and a requirement for homogeneous flow. The estimated mean vertical velocity is biased if the flow over the scanned circle is not homogeneous. It is demonstrated that the error on the mean vertical velocity due to flow inhomogeneity can be approximated by a function of the angle of the lidar beam to the vertical and the vertical gradient of the mean vertical velocity, whereas the error due to flow inhomogeneity on the horizontal mean wind speed is independent of the lidar beam angle. For the presented measurements over forest, it is evaluated that the systematic error due to the inhomogeneity of the flow is less than 0.2°. The results of the vertical conical scans were promising, and yielded positive flow angles for a sector where the forest is fetch-limited. However, more data and analysis are needed for a complete evaluation of the lidar technique.

Published
2010
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56. Climate control of terrestrial carbon exchange across biomes and continents

Author

Susumu Yamamoto, Tilden P. Meyers, Roberto Zampedri, Sonia Wharton, Krisztina Pintér, Nobuko Saigusa, Christopher B. Williams, Danilo Dragoni, João Pereira, Marc Aubinet, Gregory Starr, Janne Rinne, Jörgen Sagerfors, Alan Barr, Robert Clement, Mario B. S. Siqueira, Nina Buchmann, Lindsay B. Hutley, Laurent Misson, Jingxin Wang, Peter S. Curtis, Xinquan Zhao, Gabriel G. Katul, Leonardo Montagnani, Anders Lindroth, Thomas Foken, Stephen G. Pallardy, Haiqiang Guo, Tuomas Laurila, Casimiro Pio, M. Myklebust, Alessandro Araújo, John D. Albertson, Philippe Ciais, Christoph S. Vogel, Russell K. Monson, Werner L. Kutsch, James T. Randerson, Mika Aurela, Giorgio Matteucci, Chuixiang Yi, Ronald J. Ryel, Andrew Black, J. William Munger, Meelis Moelder, Eric Dufrêne, Christian Feigenwinter, Corinna Rebmann, Torbjoern Johansson, Fred C. Bosveld, Jiquan Chen, Benjamin Loubet, Alexander Knohl, Timothy A. Martin, J. Fuhrer, Nicolas Delpierre, Andreas Ibrom, Michael L. Goulden, Zoltán Barcza, Albin Hammerle, John Tenhunen, Lawrence B. Flanagan, Giovanni Manca, John Wolbeck, Mark A. Sutton, Paul Berbigier, Guirui Yu, William J. Massman, Ankur R. Desai, Eddy Moors, Mukufute M. Mukelabai, Christof Ammann, Hank A. Margolis, Lianhong Gu, Bernard Heinesch, Mats Nilsson, Allison L. Dunn, Ray Leuning, Zoltán Nagy, D. Bryan Dail, Shaoqiang Wang, Celso von Randow, Carole Helfter, Jason Beringer, Guenther Seufert, John Moncrieff, Hans Peter Schmid, Gerard Kiely, Luis Aires, Juha-Pekka Tuovinen, André Granier, Thomas Gruenwald, Bruce D. Cook, Georg Wohlfahrt, Thomas Kolb, Shijie Han, Xiyan Xu, Pierre Cellier, Michal V. Marek, Allen H. Goldstein, Xuefa Wen, M. S. J. Broadmeadow, Serge Rambal, Paul V. Bolstad, Ram Oren, Daniel M. Ricciuto, Tha Paw U Kyaw, Werner Eugster, Sean P. Burns, Zoltán Tuba, M. Altaf Arain, Riccardo Valentini, Corinne Jacobs, Heping Liu, Christine Moureaux, Weiguo Wang, Marjan Jongen, Runze Li, Gabriel Pita, Bin Zhao, Nigel T. Roulet, Niall P. Hanan, Christian Bernhofer, Walter C. Oechel, Harry McCaughey, Bert G. Drake, Lutz Merbold, M. Montes-Helu, Peter M. Lafleur, Asko Noormets, Jean-François Soussana, John M. Frank, Katja Klumpp, Giuseppe-Scarascia Mugnozza, Jan Elbers, Sabina Dore, Dimmie Hendriks, Mirco Migliavacca, María José Sanz, Franco Miglietta, Roser Matamala, László Haszpra, Lisa R. Welp, Damiano Gianelle, Matthew Wilkinson, Kim Pilegaard, Federica Rossi, Thomas L. Powell, Jingming Chen, Ebba Dellwik, Matthias Falk, School of Earth and Environmental Sciences, Queens College, City University of New York [New York] (CUNY), Environmental Sciences Division [Oak Ridge], Oak Ridge National Laboratory [Oak Ridge] (ORNL), UT-Battelle, LLC-UT-Battelle, LLC, Department of Statistics, Pennsylvania State University (Penn State), Penn State System-Penn State System, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), CESAM and Department of Environmental Engineering, School of Technology and Management, Polytechnic Institute of Leiria, Department of Civil and Environmental Engineering, Duke University [Durham], Agroscope, School of Geography and Earth Sciences [Hamilton ON], McMaster University [Hamilton, Ontario], Instituto Nacional de Pesquisas da Amazônia (INPA), Gembloux Agro-Bio Tech, Unit of Biosystem Physics, Université de Liège, Climate and Global Change Research [Helsinki], Finnish Meteorological Institute (FMI), Department of Meteorology [Budapest], Institute of Geography and Earth Sciences [Budapest], Faculty of Sciences [Budapest], Eötvös Loránd University (ELTE)-Eötvös Loránd University (ELTE)-Faculty of Sciences [Budapest], Eötvös Loránd University (ELTE)-Eötvös Loránd University (ELTE), Environment and Climate Change Canada, Écologie fonctionnelle et physique de l'environnement (EPHYSE), Institut National de la Recherche Agronomique (INRA), School of Geography and Environmental Science, Monash University [Clayton], Institute of Hydrology and Meteorology [Dresden], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Land and Food Systems, University of British Columbia (UBC), University of Minnesota [Twin Cities] (UMN), University of Minnesota System, Royal Netherlands Meteorological Institute (KNMI), Forest Research, Institute of Plant Science, National Center for Atmospheric Research [Boulder] (NCAR), Environnement et Grandes Cultures (EGC), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Department of Geography, University of Toronto, Department of Environmental Sciences [Toledo USA], University of Toledo, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), ICOS-ATC (ICOS-ATC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), School of Geosciences [Edinburgh], University of Edinburgh, Biospheric Sciences Laboratory, NASA Goddard Space Flight Center (GSFC), Department of Evolution, Ecology, and Organismal Biology, Ohio State University [Columbus] (OSU), Department of Plant, Soil, and Environmental Science, University of Maine, Wind Energy Division [Roskilde], Risø National Laboratory for Sustainable Energy (Risø DTU), Danmarks Tekniske Universitet = Technical University of Denmark (DTU)-Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Department of Atmospheric and Oceanic Sciences [Madison], University of Wisconsin-Madison, School of Forestry, Northern Arizona University [Flagstaff], Atmospheric Science Program, Department of Geography, Indiana University [Bloomington], Indiana University System-Indiana University System, Smithsonian Environmental Research Center (SERC), Ecologie Systématique et Evolution (ESE), Université Paris-Sud - Paris 11 (UP11)-AgroParisTech-Centre National de la Recherche Scientifique (CNRS), Department of Physical and Earth Science, Worcester State College, Wageningen University and Research [Wageningen] (WUR), Department of Land, Air and Water Resources, University of California [Davis] (UC Davis), University of California (UC)-University of California (UC), Institute for Meteorology, Climatology and Remote Sensing [Basel], University of Basel (Unibas), Department of Biological Sciences, University of Lethbridge, Micrometeorology Group [Bayreuth], Universität Bayreuth, Rocky Mountain Research Station, United States Department of Agriculture, Environment and Natural Resources Area, Istituto Agrario di San Michele all'Adige (IASMA), Department of Environmental Science, Policy, and Management [Berkeley] (ESPM), University of California [Berkeley] (UC Berkeley), Department of Earth System Science [Irvine] (ESS), University of California [Irvine] (UC Irvine), Ecologie et Ecophysiologie Forestières [devient SILVA en 2018] (EEF), Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL), Key Laboratory for Biodiversity Science and Ecological Engineering [Shanghai], Institute of Biodiversity Science at Fudan University [Shanghai] (IBSFU), Institute of Ecology, Leopold Franzens Universität Innsbruck - University of Innsbruck, Institute of Applied Ecology, Chinese Academy of Sciences [Beijing] (CAS), Natural Resource Ecology Laboratory [Fort Collins] (NREL), Colorado State University [Fort Collins] (CSU), Hungarian Meteorological Service (OMSZ), Centre for Ecology and Hydrology, Department of Hydrology and Geo-Environmental Sciences [Amsterdam], Vrije Universiteit Amsterdam [Amsterdam] (VU), School of Environmental and Life Sciences, Charles Darwin University, Biosystems Division [Roskilde], Earth System Science and Climate Change Group, Geobiosphere Science Centre, Physical Geography and Ecosystems Analysis, Lund University [Lund], Instituto Superior de Agronomia [Lisboa] (ISA), Universidade de Lisboa = University of Lisbon (ULISBOA), School of the Environment, Civil and Environmental Engineering Department, University College Cork (UCC), Unité de recherche sur l'Ecosystème Prairial (UREP), Institut für Agrarrelevante Klimaforschung, Johann Heinrich von Thünen-Institut (vTI), Trent University, CSIRO Marine and Atmospheric Research (MAR), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Department of Physics, Atmospheric Sciences and Geoscience [Jackson], Jackson State University (JSU), Institute of Atmospheric Pollution Research (IIA), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Division of Ecosystems Processes Lab. of Plants Ecological Physiology, Institute of Systems Biology and Ecology, Centre d'études de la forêt Faculté de Foresterie et de Géomatique, Université Laval [Québec] (ULaval), University of Florida [Gainesville] (UF), Biosciences Division, Argonne National Laboratory [Lemont] (ANL), Queen's University [Kingston, Canada], Max Planck Institute for Biogeochemistry (MPI-BGC), Max-Planck-Gesellschaft, ARL Atmospheric Turbulence and Diffusion Division (ATD), NOAA Air Resources Laboratory (ARL), National Oceanic and Atmospheric Administration (NOAA)-National Oceanic and Atmospheric Administration (NOAA), Remote Sensing of Environmental Dynamics Laboratory, DISAT, Università degli Studi di Milano = University of Milan (UNIMI), Instituto di Biometeorologia, Centre National de la Recherche Scientifique (CNRS), Department of Ecology and Evolutionary Biology, University of Colorado [Boulder], Servizi Forestali, Agenzia per l'Ambiente, Autonomous Province of Bolzano (APB), Faculty of Sciences and Technologies, Free University of Bozen-Bolzano, Gembloux Agro-Bio Tech, Unit of Crops Management, Zambia Meteorological Department (ZMD), Department of Earth and Planetary Sciences [Cambridge, USA] (EPS), Harvard University, Institute of Botany and Ecophysiology, Agricultural University of Gödöllô, Department of Forestry and Environmental Resources, North Carolina State University [Raleigh] (NC State), University of North Carolina System (UNC)-University of North Carolina System (UNC), Department of Biology [San Diego State Univ] (Biology SDSU), San Diego State University (SDSU), Nicholas School of the Environment and Earth Sciences, Department of Forestry, University of Missouri [Columbia] (Mizzou), University of Missouri System-University of Missouri System, Atmospheric Science Group, LAWR, CESAM and Department of Environment, Universidade de Aveiro, Mechanical Engineering Department, Instituto Superior Técnico, Universidade Técnica de Lisboa (IST), The Department of Organismic and Evolutionary Biology, Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Université Paul-Valéry - Montpellier 3 (UPVM)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Earth System Science Center, Instituto Nacional de Pesquisas Espaciais (INPE), Department of Physics, Department of Geography [Montréal], McGill University = Université McGill [Montréal, Canada], Department of Wildland Resources, Utah State University (USU), Helmholtz Zentrum für Umweltforschung = Helmholtz Centre for Environmental Research (UFZ), Centro de Estudios Ambientales del Mediterraneo, Department of Agronomy, Forestry and Land Use, Agricultural Research Council (CRA), Institut für Meteorologie und Klimaforschung - Atmosphärische Umweltforschung (IMK-IFU), Karlsruher Institut für Technologie (KIT), JRC Institute for Environment and Sustainability (IES), European Commission - Joint Research Centre [Ispra] (JRC), Collège de Direction (CODIR), University of Alabama [Tuscaloosa] (UA), Centre for Ecology and Hydrology [Edinburgh] (CEH), Natural Environment Research Council (NERC), Department of Plant Ecology, Department of Forest Environment and Resources, Università degli studi della Tuscia [Viterbo], Biological Station, University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, chine, Institute of Geographic Sciences and Natural Resource Research, IMSG@National Center for Environmental Predictions, Geosciences Research Division, Scripps Institution of Oceanography, University of California (UC), Atmospheric, Earth and Energy Division (AEED), Lawrence Livermore National Laboratory (LLNL), Graduate Degree Program in Geography, Clark University, Okayama University, Northwest Plateau Institute of Biology, City University of New-York [New-York] ( CUNY ), Environmental Sciences Division, Oak Ridge National Laboratory, PennState University [Pennsylvania] ( PSU ), Department of Forest Ecology, Swedish University of Agricultural Sciences ( SLU ), Duke university [Durham], School of Geography and Earth Sciences, Instituto Nacional de Pesquisas da Amazônia, Finnish Meteorological Institute, Climate Change Research, Department Meteorology [Budapest], Eötvös Loránd University ( ELTE ) -Eötvös Loránd University ( ELTE ), Écologie fonctionnelle et physique de l'environnement ( EPHYSE - UR1263 ), Institut National de la Recherche Agronomique ( INRA ), Institute of Hydrology and Meteorology, Technische Universität Dresden ( TUD ), University of British Columbia ( UBC ), University of Minnesota [Minneapolis], Royal Netherlands Meteorological Institute ( KNMI ), Swiss Federal Institute of Technology in Zürich ( ETH Zürich ), National Center for Atmospheric Research [Boulder] ( NCAR ), Environnement et Grandes Cultures ( EGC ), AgroParisTech-Institut National de la Recherche Agronomique ( INRA ), Department of Environmental Sciences, Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), NASA Goddard Space Flight Center ( GSFC ), Ohio State University [Columbus] ( OSU ), Risø National Laboratory for Sustainable Energy ( Risø DTU ), Technical University of Denmark [Lyngby] ( DTU ) -Technical University of Denmark [Lyngby] ( DTU ), University of Wisconsin-Madison [Madison], Smithsonian Environmental Research Center, Ecologie Systématique et Evolution ( ESE ), Université Paris-Sud - Paris 11 ( UP11 ) -AgroParisTech-Centre National de la Recherche Scientifique ( CNRS ), Wageningen University and Research Centre [Wageningen] ( WUR ), University of California Davis, Institute for Meteorology, Climatology and Remote Sensing, University of Basel ( Unibas ), Department of Micrometeorology, University of Bayreuth, Istituto Agrario di San Michele all'Adige ( IASMA ), Department of Environmental Science, Policy and Management, University of California [Berkeley], Department of Earth System Science [Irvine] ( ESS ), University of California [Irvine] ( UCI ), Ecologie et Ecophysiologie Forestières [devient SILVA en 2018] ( EEF ), Institut National de la Recherche Agronomique ( INRA ) -Université de Lorraine ( UL ), Institute of Hydrology and Meteorology, Department of Meteorology, Institute of Biodiversity Science at Fudan University [Shanghai] ( IBSFU ), University of Innsbruck, Chinese Academy of Sciences [Beijing] ( CAS ), Natural Resource Ecology Laboratory, Colorado State University [Fort Collins] ( CSU ), Hungarian Meteorological Service ( OMSz ), Department of Hydrology and Geo-Environmental Sciences, University of Amsterdam [Amsterdam] ( UvA ), Instituto Superior de Agronomia, Universidade Técnica de Lisboa, University College Cork, UR 0874 Unité de recherche sur l'Ecosystème Prairial, Institut National de la Recherche Agronomique ( INRA ) -Unité de recherche sur l'Ecosystème Prairial ( UREP ) -Ecologie des Forêts, Prairies et milieux Aquatiques ( EFPA ), Finnish Meteorological Institute ( FMI ), Marine and Atmospheric Research, Commonwealth Scientific and Industrial Research Organisation, Department of Physics, Atmospheric Sciences and Geoscience, Jackson State University, Institute of Atmospheric Pollution Research ( IIA ), Consiglio Nazionale delle Ricerche [Roma] ( CNR ), Université Laval, University of Florida [Gainesville], Argonne National Laboratory [Lemont] ( ANL ), Queen's University [Kingston], Max Planck Institute for Biogeochemistry, Atmospheric Turbulence and Diffusion Division, Università degli studi di Milano [Milano], Centre National de la Recherche Scientifique ( CNRS ), University of Colorado Boulder [Boulder], Autonomous Province of Bolzano ( APB ), Zambia Meteorological Department ( ZMD ), Division of Engineering and Applied Science, Department of Earth and Planetary Science, North Carolina State University [Raleigh] ( NCSU ), Department of Biology [San Diego], San Diego State University ( SDSU ), University of Missouri ( Saisissez le sigle en majuscules sans points ), University of Aveiro, Instituto Superior Técnico, Universidade Técnica de Lisboa ( IST ), Centre d’Ecologie Fonctionnelle et Evolutive ( CEFE ), Université Paul-Valéry - Montpellier 3 ( UM3 ) -Centre international d'études supérieures en sciences agronomiques ( Montpellier SupAgro ) -École pratique des hautes études ( EPHE ) -Institut national de la recherche agronomique [Montpellier] ( INRA Montpellier ) -Université de Montpellier ( UM ) -Centre National de la Recherche Scientifique ( CNRS ) -Institut de Recherche pour le Développement ( IRD [France-Sud] ) -Institut national d’études supérieures agronomiques de Montpellier ( Montpellier SupAgro ), Instituto Nacional de Pesquisas Espaciais ( INPE ), Université McGill, Utah State University ( USU ), Center for Global Environmental Research, National Institute for Environmental Studies ( NIES ), Agricultural Research Council ( CRA ), Institut für Meteorologie und Klimaforschung - Atmosphärische Umweltforschung ( IMK-IFU ), Karlsruher Institut für Technologie ( KIT ), JRC Institute for Environment and Sustainability ( IES ), European Commission - Joint Research Centre [Ispra] ( JRC ), UAR 0233 Collège de Direction, Institut National de la Recherche Agronomique ( INRA ) -Direction Collégiale ( DCOLL ) -Collège de Direction ( CODIR ), University of Alabama [Tuscaloosa] ( UA ), Centre for Ecology and Hydrology [Edinburgh] ( CEH ), Natural Environment Research Council ( NERC ), Tuscia University, University of California, Atmospheric, Earth and Energy Division, Lawrence Livermore National Laboratory, Écologie fonctionnelle et physique de l'environnement (EPHYSE - UR1263), Technische Universität Dresden (TUD), University of Minnesota [Twin Cities], AgroParisTech-Institut National de la Recherche Agronomique (INRA), Technical University of Denmark [Lyngby] (DTU)-Technical University of Denmark [Lyngby] (DTU), Wageningen University and Research Centre [Wageningen] (WUR), University of California-University of California, University of California [Irvine] (UCI), Hungarian Meteorological Service (OMSz), Institut National de la Recherche Agronomique (INRA)-Unité de recherche sur l'Ecosystème Prairial (UREP)-Ecologie des Forêts, Prairies et milieux Aquatiques (EFPA), Consiglio Nazionale delle Ricerche [Roma] (CNR), Harvard University [Cambridge], University of Missouri [Columbia], Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Paul-Valéry - Montpellier 3 (UM3), McGill University, Helmholtz Centre for Environmental Research (UFZ), Institut National de la Recherche Agronomique (INRA)-Direction Collégiale (DCOLL)-Collège de Direction (CODIR), Université Paul-Valéry - Montpellier 3 (UM3)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-École pratique des hautes études (EPHE)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Università degli Studi di Milano [Milano] (UNIMI), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Université Paul-Valéry - Montpellier 3 (UPVM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut de Recherche pour le Développement (IRD [France-Sud]), Hydrology and Geo-environmental sciences, and Earth and Climate

Subjects
010504 meteorology & atmospheric sciences, [SDV]Life Sciences [q-bio], Biome, UNCERTAINTY, Carbon sequestration, eddy flux photosynthesis, soil respiration, 01 natural sciences, Biomes, EDDY FUX, Soil respiration, SDG 13 - Climate Action, CWK - Earth System Science and Climate Change, Wageningen Environmental Research, Biosystemer, Photosynthesis, uncertainty, TEMPERATURE, SDG 15 - Life on Land, General Environmental Science, Carbon dioxide in Earth's atmosphere, changement climatique, Respiration, Temperature, Dryness, Global Carbon Cycle, TERRESTRIAL CARBON SEQUESTRATION, facteur climatique, Forestry, Climate Control, deciduous forest, 04 agricultural and veterinary sciences, fluxes, RESPIRATION, Climatology, Terrestrial ecosystem, eddy-covariance measurements, INTERANNUAL VARIABILITY, CLIMATE CONTROL, BIOMES, SOIL RESPIRATION, DIOXIDE, cycle du carbone, Carbon Sequestration, FLUXES, effet de serre, LONG-TERM, interannual variability, SPATIAL VARIABILITY, education, water-vapor, Eddy covariance, DRYNESS, Miljø og klima, Eddy Fluxes, 114 Physical sciences, écosystème, Ecosystems, Carbon cycle, NET ECOSYSTEM EXCHANGE, NEE, climate control, terrestrial carbon sequestration, temperature, dryness, eddy flux, biomes, photosynthesis, respiration, global carbon cycle, dioxide, bilan de carbone, température, Ecosystem, 0105 earth and related environmental sciences, Nee, long-term, [ SDV ] Life Sciences [q-bio], EDDY-COVARIANCE MEASUREMENTS, Renewable Energy, Sustainability and the Environment, PHOTOSYNTHESIS, Public Health, Environmental and Occupational Health, Carbon Dioxide, 15. Life on land, CWC - Earth System Science and Climate Change, Carbon, DECIDUOUS FOREST, GLOBAL CARBON CYCLE, flux, WATER-VAPOR, 13. Climate action, Atmospheric Chemistry, 040103 agronomy & agriculture, 0401 agriculture, forestry, and fisheries, Environmental science, Eddy flux, spatial variability
Abstract

Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid-and high-latitudes, (2) a strong function of dryness at mid-and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 degrees N). The sensitivity of NEE to mean annual temperature breaks down at similar to 16 degrees C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.

Published
2010
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57. Methanol and other VOC fluxes from a Danish beech forest during springtime

Author

S. J. Solomon, Gunnar W. Schade, Ebba Dellwik, Kim Pilegaard, and A. Ladstätter-Weissenmayer

Subjects
Canopy, biology, Atmospheric sciences, biology.organism_classification, chemistry.chemical_compound, chemistry, Fagus sylvatica, Diurnal cycle, Mixing ratio, Environmental science, Methanol, Sink (computing), Deposition (chemistry), Beech
Abstract

In-canopy mixing ratio gradients and above-canopy fluxes of several volatile organic compounds (VOCs) were measured using a commercial proton transfer reaction mass spectrometer (PTR-MS) in a European beech (Fagus sylvatica) forest in Denmark. Emission fluxes of methanol occurred dominantly late at night, which was supported by highest mixing ratios in the crown region, and is in line with recent controlled laboratory experiments. Also confirming previous measurements, monoterpene emissions showed a diurnal cycle consistent with light-dependent emissions, supported by highest mixing ratios in the canopy space during early afternoon. Also emitted was acetone, but only at ambient temperatures exceeding 20°C. Deposition dominated at lower temperatures. Deposition fluxes occurred also for methanol but seemingly as a result of high ambient methanol mixing ratios. Our in-canopy gradient measurements contrasted earlier results from tropical and pine forest ecosystems in that they did not show this beech ecosystem to be a strong sink for oxygenated VOCs. Instead, their gradients were flat and only small deposition velocities (

Published
2008
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58. Turbulence spectra, shear stress and turbulent kinetic energy budgets above two beech forest sites in Denmark

Author

Niels Otto Jensen, Ebba Dellwik, and Ivan Mammarella

Subjects
Length scale, Atmospheric Science, Meteorology, 010504 meteorology & atmospheric sciences, Turbulence, Flow (psychology), 010501 environmental sciences, Dissipation, 15. Life on land, Atmospheric sciences, 01 natural sciences, Boundary layer, Turbulence kinetic energy, Shear stress, Environmental science, Scaling, 0105 earth and related environmental sciences
Abstract

The focus of this study is the combined influence of the roughness sublayer (RSL) found above tall vegetation and the internal boundary layer (IBL) on the near-neutral flow above two forest sites. Measurements of the 3-D wind field from masts about twice the forest height were analysed. For both sites, influence from upwind conditions was detected for a short-fetch sector. For one of the sites, an additional long-fetch sector without significant IBL influence is presented. Spectral analysis, dissipation length scale analysis and evaluation of the most important terms in the turbulent kinetic energy and shear stress budgets, were performed. For all selected sectors, RSL influence was detected close to the canopy top: the dissipation length scale was greater than the height above the displacement height of the forest, and the turbulent transport terms were significant. For the short-fetch sectors, the spectral analysis of measurements taken in the RSL and in the IBL (above the RSL) showed that scaling by fixed length and velocity scales resulted in a good collapse of the spectral peaks. For the long-fetch sector, the RSL influence disappeared at greater heights, and the flow is nearly adjusted with the new surface. DOI: 10.1111/j.1600-0889.2007.00326.x

Published
2008
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59. Quality control of CarboEurope flux data – Part I: Footprint analyses to evaluate sites in forest ecosystems

Author

André Granier, Michal V. Marek, Leonardo Montagnani, R. Koeble, Alexander Knohl, Werner Eugster, J. Banza, Tuomas Laurila, Matthias Mauder, Ebba Dellwik, Mathias Göckede, Eddy Moors, Serge Rambal, Jean-Marc Ourcival, Yves Brunet, Jean-Marc Bonnefond, Dan Yakir, María José Sanz, John Moncrieff, Giovanni Manca, Arnaud Carrara, Eyal Rotenberg, Jan Elbers, Bernard Heinesch, G. Seufert, Hans Verbeeck, Giorgio Matteucci, Mika Aurela, J. Fuhrer, Pavel Sedlák, Timo Vesala, Gabriel Pita, Corinna Rebmann, Christian Bernhofer, João Mateus, Lukas Siebicke, Tiina Markkanen, Stefano Minerbi, Riccardo Valentini, Robert Clement, Mirco Migliavacca, Ivan A. Janssens, Kim Pilegaard, Jean-François Soussana, Dario Papale, João Pereira, Abel Rodrigues, M. Aubinet, Thomas Foken, B. Longdoz, and Thomas Grünwald

Subjects
010504 meteorology & atmospheric sciences, 0207 environmental engineering, Flux, Terrain, 02 engineering and technology, Land cover, 15. Life on land, Sensible heat, 01 natural sciences, Footprint, Latent heat, Data quality, Spatial ecology, Environmental science, 020701 environmental engineering, 0105 earth and related environmental sciences, Remote sensing
Abstract

We applied a site evaluation approach combining Lagrangian Stochastic footprint modelling with a quality assessment approach for eddy-covariance data to 25 forested sites of the CarboEurope-IP network. The analysis addresses the spatial representativeness of the flux measurements, instrumental effects on data quality, spatial patterns in the data quality, and the performance of the coordinate rotation method. Our findings demonstrate that application of a footprint filter could strengthen the CarboEurope-IP flux database, since only one third of the sites is situated in truly homogeneous terrain. Almost half of the sites experience a significant reduction in eddy-covariance data quality under certain conditions, though these effects are mostly constricted to a small portion of the dataset. Reductions in data quality of the sensible heat flux are mostly induced by characteristics of the surrounding terrain, while the latent heat flux is subject to instrumentation-related problems. The Planar-Fit coordinate rotation proved to be a reliable tool for the majority of the sites using only a single set of rotation angles. Overall, we found a high average data quality for the CarboEurope-IP network, with good representativeness of the measurement data for the specified target land cover types.

Published
2007
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60. On the use of the Webb–Pearman–Leuning theory for closed-path eddy correlation measurements

Author

Kim Pilegaard, Søren Ejling Larsen, Ebba Dellwik, and Andreas Ibrom

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Scalar (mathematics), Eddy covariance, 010501 environmental sciences, 01 natural sciences, Wind speed, Dilution, Computational physics, Flux (metallurgy), Amplitude, Closed path, Water vapor, 0105 earth and related environmental sciences, Mathematics
Abstract

We consider an imperfection of real closed-path eddy correlation systems—the decoupling of the water vapour and CO 2 concentrations—with respect to the application of the Webb–Pearman–Leuning (WPL) theory. It is described why and how the current application of the WPL theory needs to be adapted to the processes in closed-path sensors. We show the quantitative effects of applying the WPL theory in different ways using CO 2 flux measurements taken above the Danish Beech forest CarboEurope site near Soro, Zealand. Using the WPL theory in closed-path sensors without taking amplitude damping and decoupling into account, overcorrected the annual flux by 21%, or 31 g m -2 yr -1 , to which the decoupling effect contributed with 7%. We suggest either converting the raw data point-by-point to mixing ratios or using the uncorrected covariances of water vapour mole fractions with the vertical wind velocity that were calculated with the same time lag as for the scalar concentration when correcting the dilution effect. We showed that the two approaches yielded equivalent flux results. Correct ways of applying spectral corrections to CO 2 fluxes calculated in either way are also shown. The findings reported here do not apply to open-path sensors. DOI: 10.1111/j.1600-0889.2007.00311.x

Published
2007
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61. The Science of Making Torque from Wind 2014 (TORQUE 2014)

Author

Jakob Mann, Helge Aagaard Madsen, Gunner Chr. Larsen, Ole Rathmann, Ameya Sathe, Gregor Giebel, Jens Nørkær Sørensen, Anand Natarajan, Martin Otto Laver Hansen, Andreas Bechmann, Ebba Dellwik, Nikolay Krasimirov Dimitrov, Ferhat Bingöl, Christian Bak, Dorte Juul Jensen, and Niels N. Sørensen

Subjects
Wind-turbine aerodynamics, History, Engineering, Wind power, Higher education, Operations research, business.industry, Global warming, Consumption (sociology), Computer Science Applications, Education, Management, Work (electrical), Torque, Christian ministry, business
Abstract

The 186 papers in this volume constitute the proceedings of the fifth Science of Making Torque from Wind conference, which is organized by the European Academy of Wind Energy (EAWE, www.eawe.eu). The conference, also called Torque 2014, is held at the Technical University of Denmark (DTU) 17–20 June 2014. The EAWE conference series started in 2004 in Delft, the Netherlands. In 2007 it was held in Copenhagen, in 2010 in Heraklion, Greece, and then in 2012 in Oldenburg, Germany. The global yearly production of electrical energy by wind turbines has grown approximately by 25% annually over the last couple of decades and covers now 2–3% of the global electrical power consumption. In order to make a significant impact on one of the large challenges of our time, namely global warming, the growth has to continue for a decade or two yet. This in turn requires research and education in wind turbine aerodynamics and wind resources, the two topics which are the main subjects of this conference. Similar to the growth in electrical power production by wind is the growth in scientific papers about wind energy. Over the last decade the number of papers has also grown by about 25% annually, and many research based companies all over the world are founded. Hence, the wind energy research community is rapidly expanding and the Torque conference series offers a good opportunity to meet and exchange ideas. We hope that the Torque 2014 will heighten the quality of the wind energy research, while the participants will enjoy each others company in Copenhagen. Many people have been involved in producing the Torque 2014 proceedings. The work by more than two hundred reviewers ensuring the quality of the papers is greatly appreciated. The timely evaluation and coordination of the reviews would not have been possible without the work of sixteen ''section editors'' all from DTU Wind Energy: Christian Bak, Andreas Bechmann, Ferhat Bingol, Ebba Dellwik, Nikolay Dimitrov, Gregor Giebel, Martin O L Hansen, Dorte Juul Jensen, Gunner Larsen, Helge Aagaard Madsen, Jakob Mann, Anand Natarajan, Ole Rathmann, Ameya Sathe, Jens Norkaer Sorensen and Niels Norkaer Sorensen, who are all co-editors of these proceedings. The resources provided by the Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence funded by the Danish Council for Strategic Research grant no. 09-067216 and the Danish Ministry of Science, Innovation and Higher Education Technology and Production, grant no. 11- 117018 are gratefully acknowledged. We are also immensely indebted to the very responsive help and support from the editorial team at IoP, especially Sarah Toms and Anete Ashton, during the reviewing process of these proceedings. We are looking forward to meeting you in Copenhagen and also to Torque 2016, which will take place at the Technical University of Munich, Germany. Roskilde, Denmark, June 2014 Ebba Dellwik, Ameya Sathe and Jakob Mann Technical University of Denmark

Published
2014
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62. Sudden distortion of turbulence at a forest edge

Author

Ebba Dellwik and Jakob Mann

Subjects
Canopy, History, Meteorology, Turbulence, Flow (psychology), Edge (geometry), Atmospheric sciences, Wind speed, Computer Science Applications, Education, Physics::Fluid Dynamics, Geography, Anemometer, Distortion, Overshoot (signal)
Abstract

Dellwik et al. (2013) presented data from a forest edge experiment based on two meteorological towers instrumented with sonic anemometers. The experiment was performed at a dense edge of the Tromnaes Forest, which is a 24 m tall mature beech stand on the island Falster, Denmark. The topography at the site is flat. The towers were placed approximately 1.5 canopy heights upwind and downwind of the edge, respectively, and were two canopy heights tall. For near-neutral, near-perpendicular flow towards the edge, one finding concerned that although the wind speed gradients were similar before and after the edge, the momentum flux was strongly reduced above the canopy. This is contrary to the results by standard Reynolds' averaged Navier-Stokes models that predict an overshoot of the momentum flux. Further, a reduction of the vertical variance of the flow was largely compensated by an increase in the lateral variance, whereas the streamwise variance remained approximately constant. This result is in contrast to the predictions by homogeneous rapid distortion theory. We apply and develop an alternative framework based on inhomogeneous rapid distortion theory, also called blocking, in combination with the turbulence model by Mann (1994), and investigate whether this model can predict the observed changes of the flow. The presented results are relevant for understanding the rapid changes of turbulence in the heterogeneous landscape.

Published
2014
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63. Meso-scale modeling of a forested landscape

Author

Andrea N. Hahmann, Ebba Dellwik, Stefan Söderberg, Matthias Mohr, Hans Bergström, and Johan Arnqvist

Subjects
Mast (sailing), History, Geography, Meteorology, Planetary boundary layer, Anemometer, Weather Research and Forecasting Model, Wind shear, Meteorological instrumentation, Land cover, Wind direction, Computer Science Applications, Education
Abstract

Meso-scale models are increasingly used for estimating wind resources for wind turbine siting. In this study, we investigate how the Weather Research and Forecasting (WRF) model performs using standard model settings in two different planetary boundary layer schemes for a forested landscape and how this performance is changed when enhancing the roughness by a factor four in one of the schemes. The model simulations were evaluated using data from a 138 m tall mast in southeastern Sweden, where an experiment with six sonic anemometers and standard meteorological instrumentation was performed 2010-2012. The land cover around the mast is dominated by forest and for the most common wind direction, the forest extends more than 200 km from the mast. The two low-roughness simulations showed differences both in terms of estimated wind resource and wind shear. The simulation with enhanced roughness results in an improved correlation with measured data for near-neutral situations in the observed height range, whereas the correlation is deteriorated relative to the standard setup for stable atmospheric stratifications for heights above approximately 80 m. The inclusion of the displacement height in the post-processing of the results is also discussed.

Published
2014
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66. Laser measurements of flow over a forest

Author

Ferhat Bingöl, Jakob Mann, Ole Rathmann, and Ebba Dellwik

Subjects
History, Wind power, Wind gradient, Meteorology, business.industry, Computational fluid dynamics, Turbine, Wind speed, Computer Science Applications, Education, Wind profile power law, Geography, Wind shear, Turbulence kinetic energy, business
Abstract

It is estimated that 20–30% of the total European wind energy growth takes place in areas where the wind flow is affected by forests. The description of the wind conditions near and above forests poses a challenge, since assumptions of classical boundary-layer theory are violated. Turbines are designed for a maximal turbulence intensity and wind profile gradient. In forested areas, these limits are often violated possibly leading to reduced turbine life-time. In this paper we investigate the mean wind profile and turbulence statistics above an 85 years old dense beech forest by use of a laser Doppler anemometer and compare the profiles with a CFD model specifically made for the modeling of flow over vegetation canopies.

Published
2008
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67. Sentinel-1 SAR for wind energy roughness maps over land

Author

Ebba Dellwik, Ioanna Karagali, Elin Svensson, Henning Skriver, and Merete Badger

Abstract

For the wind energy application, updated information on aerodynamic surface roughness is important for an accurate prediction of the land surface effect on the atmosphere. Tall wind turbines are commonly sited in forested areas, and since the forest both increase turbulence levels and decrease the wind resource, the parametrization of forest roughness in wind models is of high relevance. Here, we investigate whether the Sentinel-1 SAR images can be used to identify high-roughness forested areas. The backscatter properties of the SAR images are compared to digital surface models and vegetation density maps derived from near-concurrent aerial lidar scans (ALS). These ALS products have previously shown good results in wind models for the wind energy application, but the scans are costly to perform and therefore typically only represent a snapshot in time, whereas the Sentinel mission SAR images provide frequent updated information. We investigate how the SAR images vary with season over both deciduous and needle-leaf forests and in addition test whether nearby meteorological observations can explain image to image differences in the backscatter level. In order to understand the backscatter level, new products from the ALS point cloud are derived and compared with the SAR images. This part of the work is focused on whether we also can quantify the roughness based on the SAR backscatter. Since SAR images are affected by speckle noise, they are averaged over monthly and bimonthly intervals after careful inspection of each image. The work is focused on the Østerild test site for large wind turbines in Northern Denmark, where extensive wind experiments have been performed.

73. Comparison of net CO2 fluxes measured with open- and closed-path infrared gas analyzers in an urban complex environment

Author

Leena Järvi, Ivan Mammarella, Werner Eugster, Andreas Ibrom, Erkki Siivola, Ebba Dellwik, Petri Ilkka Rinaldo Keronen, George Burba, and Timo Vesala

Subjects
Greenhouse gasses, Økosystemer, klimaeffekter, drivhusgasser, Bio energy, SDG 13 - Climate Action, Bioenergi, Climate effects, Ecosystems
Abstract

Simultaneous eddy covariance (EC) measurements of CO2 fluxes made with open-path and closed-path analyzers were done in urban area of Helsinki, Finland, in July 2007–June 2008. Our purpose was to study the differences between the two analyzers, the necessary correction procedures and their suitability to accurately measure CO2 exchange in such non-ideal landscape. In addition, this study examined the effect of open-path sensor heating on measured fluxes in urban terrain, and these results were compared with similar measurements made above a temperate beech forest in Denmark. The correlation between the two fluxes was good (R2 = 0.93) at the urban site, but during the measurement period the open-path net surface exchange (NSE) was 17% smaller than the closed-path NSE, indicating apparent additional uptake of CO2 by open-path measurements. At both sites, sensor heating corrections evidently improved the performance of the open-path analyzer by reducing discrepancies in NSE at the urban site to 2% and decreasing the difference in NSE from 67% to 7% at the forest site. Overall, the site-specific approach gave the best results at both sites and, if possible, it should be preferred in the sensor heating correction.

78. Lidars in wind energy

Author

Jakob Mann, Ferhat Bingöl, Torben Krogh Mikkelsen, Ioannis Antoniou, Michael Courtney, Gunner Larsen, Ebba Dellwik, Trujillo, J. J., and Hans Ejsing Jørgensen

79. Numerical modeling of the airflow around a forest edge using LiDAR-derived forest heigths

Author

Louis-Etienne Boudreault, Ebba Dellwik, Andreas Bechmann, Sørensen, Niels N., and Andrey Sogachev

Subjects
Wind turbine siting, Digital elevation model, Computational fluid dynamics, Forest canopy flow, Light detection and ranging
Abstract

A 3D methodology to quantify the effect of forests on the mean wind flow field is presented. The methodology is based on the treatment of forest raw data of light detection and ranging (LiDAR) scans, and a computational fluid dynamics (CFD) method based on a Reynolds-averaged Navier-Stokes (RaNS) approach using the k−e turbulence model with a corresponding canopy model. The examplesite investigated is a forest edge located on the Falster island in Denmark, where a measurement campaign was conducted. The LiDAR scans are used in order to obtain the forest heights, which served as input to the numerical CFD model. A sensitivity analysis with regards to the resolution of the structured forest height grid obtained from the implemented digital elevation model (DEM) was carried out. CFD calculations were conducted with the forest height grid taken as input and the complete methodology results are finally briefly compared to the wind measurements of the site with regards to the calculated wind field prediction accuracy.

80. Field test of an all-semiconductor laser-based coherent continuous-wave Doppler lidar for wind energy applications

Author

Mikael Sjöholm, Ebba Dellwik, Qi Hu, Jakob Mann, Christian Pedersen, and Peter John Rodrigo

Subjects
Wind turbine control, All-semiconductor laser, Volume averaging, Coherent Doppler lidar
Abstract

The wind energy industry is gaining interest in prevision of the rotor inflow for turbine control. The potential benefits are increased power production due to better alignment of the rotor to the mean wind direction as well as prolonged lifetime of the turbine due to load reductions. Several lidar-based instruments for wind turbine mounting are now commercially available. However, they suffer from high price and bulkiness. Therefore, the Technical University of Denmark has, in collaboration with the Danish company Windar Photonics A/S, developed a compact and low-cost lidar called WindEye based on a mass-produced all-semiconductor laser. The instrument is a coherent continuous-wave lidar with two fixed-focus telescopes for launching laser beams in two different directions. The alternation between the telescopes is achieved by a novel switching technique without any moving parts. Here, we report results from comparison campaigns with ultrasonic anemometer (METEK USA-1, Germany) measurements at a distance of about 80 meters from the lidar instrument. The influence of the finite spatial sampling volume at this range on the measured wind spectra is demonstrated. The sampling volume in the latest version of the instrument has been narrowed due to an improved telescope design and the signal quality has improved. Good reliability is essential for the anticipated applications for wind turbines. Thus, the lidar has been tested over extended periods in various meteorological conditions and the influence on the lidar signal strength from external atmospheric parameters such as relative humidity and concentrations of atmospheric particles is discussed. This novel lidar instrument design seems to offer a promising low-cost alternative for prevision remote sensing of wind turbine inflow.

89. Synchronized agile beam scanning of coherent continuous-wave doppler lidars for high-resolution wind field characterization

Author

Mikael Sjöholm, Nikolas Angelou, Michael Courtney, Ebba Dellwik, Jakob Mann, Torben Krogh Mikkelsen, and Anders Tegtmeier Pedersen

Subjects
Doppler wind lidar, Double-prism scanner, Synchronized multiple beam scanning, Continuous-wave lidar, Windscanner
Abstract

Developments of coherent continuous-wave lidar technologies for detailed studies of the three components of wind fields in the three-dimensional space has been pursued at DTU Wind Energy during the last decade with a concept called WindScanner. Since a single lidar only measures the wind component along the laser beam, the concept builds on synchronized agile beam-scanning of several lidars. The technological developments including synchronized double-prism-based scanning and an all-fiber in-phase and quadrature direction detection scheme are described. Several different instrument implementations have been realized and application examples from wind energy, structural design, aviation, boundary-layer meteorology, and recently also forestry and detailed studies in wind tunnels are highlighted. The wind lidar developments has not only proven to provide useful remote-sensing tools for wind field characterization at high spatial and temporal resolution but also holds prospects as tools for calibrating traditional point-monitoring anemometric devices which currently is investigated.

90. Implementing earth observation and advanced satellite based atmospheric sounders for water resource and climate modelling

Author

Boegh, E., Ebba Dellwik, Hahmann, Andrea N., Charlotte Bay Hasager, Joakim Refslund Nielsen, and Dan Rosbjerg

Subjects
Wind power meteorology, Vindenergi, Wind energy, Vindkraftmeteorologi
Abstract

This paper discusses preliminary remote sensing (MODIS) based hydrological modelling results for the Danish island Sjælland (7330 km2) in relation to project objectives and methodologies of a new research project “Implementing Earth observation and advanced satellite based atmospheric sounders for effective land surface representation in water resource modeling” (2009- 2012). The purpose of the new research project is to develop remote sensing based model tools capable of quantifying the relative effects of site-specific land use change and climate variability at different spatial scales. For this purpose, a) internal catchment processes will be studied using a Distributed Temperature Sensing (DTS) system, b) Earth observations will be used to upscale from field to regional scales, and c) at the largest scale, satellite based atmospheric sounders and meso-scale climate modelling will be used to study and verify the modelling of land surface hydrology processes.

95. Characterization of a tree wake using three short-range WindScanners

Author

Nikolas Angelou, Ebba Dellwik, and Jakob Mann

Abstract

The presence of solitary trees in a flat terrain introduce heterogeneities, which modify the characteristics of the wind. Trees act like obstacles that extract energy from the mean flow and increase the turbulence of the wind. This has an impact on the momentum flux and thus is of particular interest in climate related studies. Furthermore, the wind-trees interaction is a topic of study also in applied research areas, like wind energy, where the estimation of wind resources and associated turbulence levels is necessary to describe accurately the wind conditions over an area. In the case of rough landscapes typical uncertainties in the estimation of the terrain roughness can result to 10% uncertainty in the annual energy production estimate [1]. In order to contribute to the understanding of the aforementioned topics a project called Single Tree was initiated in the Wind Energy Department of the Technical University of Denmark (DTU), with the objective to characterize the flow around a solitary tree. For the needs of this study a European Oak tree (Quercus robur), located on the shore of the Roskilde fjord in Denmark, was selected. Such a tree is commonly found in forests or solitarily in urban and rural environments in temperate regions. Using a commercial terrestrial laser scanner, the dimensions and the detailed geometry of the tree were measured (see Figure 1 and Figure 2, left) and two meteorological masts equipped with multiple in-situ sonic anemometers were used to provide reference measurements of the wind conditions. A phenomenon that describes the wind-trees interaction is the wake of a tree, since it is the result of the momentum extracted from the wind due to the presence of the tree, which acts as a porous obstacle with a complex geometry. This complex geometry creates challenges in the numerical prediction of wind-trees interactions and thus the generation of high quality experimental flow data is paramount. Such an investigation is feasible using three short-range WindScanners, which are mobile remote sensing instruments developed in the Wind Energy Department of DTU [2].

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