Author
Petri Keronen
Other affiliations: Finnish Meteorological Institute
Bio: Petri Keronen is an academic researcher from University of Helsinki. The author has contributed to research in topics: Aerosol & Eddy covariance. The author has an hindex of 43, co-authored 108 publications receiving 10474 citations. Previous affiliations of Petri Keronen include Finnish Meteorological Institute.
Papers published on a yearly basis
Papers
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TL;DR: An increase in future drought events could turn temperate ecosystems into carbon sources, contributing to positive carbon-climate feedbacks already anticipated in the tropics and at high latitudes.
Abstract: Future climate warming is expected to enhance plant growth in temperate ecosystems and to increase carbon sequestration. But although severe regional heatwaves may become more frequent in a changing climate their impact on terrestrial carbon cycling is unclear. Here we report measurements of ecosystem carbon dioxide fluxes, remotely sensed radiation absorbed by plants, and country-level crop yields taken during the European heatwave in 2003.We use a terrestrial biosphere simulation model to assess continental-scale changes in primary productivity during 2003, and their consequences for the net carbon balance. We estimate a 30 per cent reduction in gross primary productivity over Europe, which resulted in a strong anomalous net source of carbon dioxide (0.5 Pg Cyr21) to the atmosphere and reversed the effect of four years of net ecosystem carbon sequestration. Our results suggest that productivity reduction in eastern and western Europe can be explained by rainfall deficit and extreme summer heat, respectively. We also find that ecosystem respiration decreased together with gross primary productivity, rather than accelerating with the temperature rise. Model results, corroborated by historical records of crop yields, suggest that such a reduction in Europe's primary productivity is unprecedented during the last century. An increase in future drought events could turn temperate ecosystems into carbon sources, contributing to positive carbon-climate feedbacks already anticipated in the tropics and at high latitudes.
3,408 citations
University of California, Berkeley1, Oak Ridge National Laboratory2, Oregon State University3, Gembloux Agro-Bio Tech4, Dresden University of Technology5, University of Nebraska–Lincoln6, University of Antwerp7, Institut national de la recherche agronomique8, United States Forest Service9, Duke University10, University of Edinburgh11, Harvard University12, University of Helsinki13, Max Planck Society14, University of Bayreuth15, University of New Hampshire16
TL;DR: In this paper, the impact of different gap filling methods on the annual sum of net ecosystem exchange (F NEE ) responses is investigated, based on mean diurnal variation, look-up tables (LookUp), and nonlinear regressions (Regr).
1,717 citations
Institut national de la recherche agronomique1, Max Planck Society2, University of Antwerp3, University of Bayreuth4, Dresden University of Technology5, École Polytechnique Fédérale de Lausanne6, Finnish Forest Research Institute7, University of Helsinki8, Lund University9, Instituto Superior Técnico10, Centre national de la recherche scientifique11
TL;DR: In this paper, the authors used continuous carbon and water flux measurements at 12 European monitoring sites covering various forest ecosystem types and a large climatic range in order to characterise the consequences of this drought on ecosystems functioning.
580 citations
University of California, Berkeley1, Oak Ridge National Laboratory2, Oregon State University3, Dresden University of Technology4, University of Nebraska–Lincoln5, University of Antwerp6, University of Edinburgh7, Institut national de la recherche agronomique8, United States Forest Service9, Duke University10, University of Helsinki11, Harvard University12, Max Planck Society13, University of Bayreuth14, University of New Hampshire15
TL;DR: In this article, the authors adapted methods of gap filling for NEE (net ecosystem exchange of carbon) to energy fluxes and applied them to data sets available from the EUROFLUX and AmeriFlux eddy covariance databases.
531 citations
TL;DR: In this paper, the authors investigated the connection between forest-atmosphere carbon exchange and aerosol dynamics in the continental boundary layer by means of multiannual data sets of particle formation and growth rates, of CO2 fluxes, and of monoterpene concentrations in a Scots pine forest in southern Finland.
Abstract: . The possible connections between the carbon balance of ecosystems and aerosol-cloud-climate interactions play a significant role in climate change studies. Carbon dioxide is a greenhouse gas, whereas the net effect of atmospheric aerosols is to cool the climate. Here, we investigated the connection between forest-atmosphere carbon exchange and aerosol dynamics in the continental boundary layer by means of multiannual data sets of particle formation and growth rates, of CO2 fluxes, and of monoterpene concentrations in a Scots pine forest in southern Finland. We suggest a new, interesting link and a potentially important feedback among forest ecosystem functioning, aerosols, and climate: Considering that globally increasing temperatures and CO2 fertilization are likely to lead to increased photosynthesis and forest growth, an increase in forest biomass would increase emissions of non-methane biogenic volatile organic compounds and thereby enhance organic aerosol production. This feedback mechanism couples the climate effect of CO2 with that of aerosols in a novel way.
353 citations
Cited by
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United States Geological Survey1, University of Arizona2, University of Batna3, Oregon State University4, Los Alamos National Laboratory5, Centre national de la recherche scientifique6, Swiss Federal Institute for Forest, Snow and Landscape Research7, Natural Resources Canada8, University of California, Berkeley9, University of Granada10, Northern Research Institute11, Forest Research Institute12, Food and Agriculture Organization13, University of Montana14, Northern Arizona University15
TL;DR: In this paper, the authors present the first global assessment of recent tree mortality attributed to drought and heat stress and identify key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system.
5,811 citations
TL;DR: Interdisciplinary science that integrates knowledge of the many interacting climate services of forests with the impacts of global change is necessary to identify and understand as yet unexplored feedbacks in the Earth system and the potential of forests to mitigate climate change.
Abstract: The world's forests influence climate through physical, chemical, and biological processes that affect planetary energetics, the hydrologic cycle, and atmospheric composition. These complex and nonlinear forest-atmosphere interactions can dampen or amplify anthropogenic climate change. Tropical, temperate, and boreal reforestation and afforestation attenuate global warming through carbon sequestration. Biogeophysical feedbacks can enhance or diminish this negative climate forcing. Tropical forests mitigate warming through evaporative cooling, but the low albedo of boreal forests is a positive climate forcing. The evaporative effect of temperate forests is unclear. The net climate forcing from these and other processes is not known. Forests are under tremendous pressure from global change. Interdisciplinary science that integrates knowledge of the many interacting climate services of forests with the impacts of global change is necessary to identify and understand as yet unexplored feedbacks in the Earth system and the potential of forests to mitigate climate change.
4,541 citations
TL;DR: In this paper, the authors provide a synthesis of past research on the role of soil moisture for the climate system, based both on modelling and observational studies, focusing on soil moisture-temperature and soil moistureprecipitation feedbacks, and their possible modifications with climate change.
3,402 citations
University of Gothenburg1, University College Cork2, Paul Scherrer Institute3, Weizmann Institute of Science4, Norwegian Meteorological Institute5, Chalmers University of Technology6, University of Antwerp7, Carnegie Mellon University8, University of Lyon9, Centre national de la recherche scientifique10, University of California, Berkeley11, University of York12, Leibniz Institute for Neurobiology13, University of Mainz14, University of Florida15, University of Colorado Boulder16, Forschungszentrum Jülich17, Ghent University18, University of Manchester19, Aix-Marseille University20, California Institute of Technology21
TL;DR: In this article, an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and analytical techniques used to determine the chemical composition of SOA is presented.
Abstract: Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.
3,324 citations
TL;DR: A hydraulically based theory considering carbon balance and insect resistance that allowed development and examination of hypotheses regarding survival and mortality was developed, and incorporating this hydraulic framework may be effective for modeling plant survival andortality under future climate conditions.
Abstract: Summary Severe droughts have been associated with regional-scale forest mortality worldwide. Climate change is expected to exacerbate regional mortality events; however, pre- diction remains difficult because the physiological mechanisms underlying drought survival and mortality are poorly understood. We developed a hydraulically based theory considering carbon balance and insect resistance that allowed development and examination of hypotheses regarding survival and mortality. Multiple mechanisms may cause mortality during drought. A common mechanism for plants with isohydric
3,302 citations