N. Viovy
Commissariat à l'Energie Atomique (CEA), LSCE, Department Member
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT- An Ensemble method is presented for assimilating AVHRR/NDVI data to correct the Leaf Area Index (LAI) simulated by the dynamic biosphere model ORCHIDEE/STOMATE. The corrected LAIs over Europe are shown, as well as the... more
ABSTRACT- An Ensemble method is presented for assimilating AVHRR/NDVI data to correct the Leaf Area Index (LAI) simulated by the dynamic biosphere model ORCHIDEE/STOMATE. The corrected LAIs over Europe are shown, as well as the consequences on the Net Primary Production. 1.
Research Interests: Geography, Environmental Science, Climate Change, Climatology, Photosynthesis, and 15 moreEnvironmental Monitoring, Climate, Medicine, Multidisciplinary, Global Warming, Arctic, Computer Simulation, Plants, Droughts, Northern Hemisphere, Ecosystem, Arctic Vegetation, Nature Communications, Growing Season, and Normalized Difference Vegetation Index
Carbon Cycle and Climate Change As climate change accelerates, it is important to know the likely impact of climate change on the carbon cycle (see the Perspective by Reich ). Gross primary production (GPP) is a measure of the amount of... more
Carbon Cycle and Climate Change As climate change accelerates, it is important to know the likely impact of climate change on the carbon cycle (see the Perspective by Reich ). Gross primary production (GPP) is a measure of the amount of CO 2 removed from the atmosphere every year to fuel photosynthesis. Beer et al. (p. 834 , published online 5 July) used a combination of observation and calculation to estimate that the total GPP by terrestrial plants is around 122 billion tons per year; in comparison, burning fossil fuels emits about 7 billion tons annually. Thirty-two percent of this uptake occurs in tropical forests, and precipitation controls carbon uptake in more than 40% of vegetated land. The temperature sensitivity (Q10) of ecosystem respiratory processes is a key determinant of the interaction between climate and the carbon cycle. Mahecha et al. (p. 838 , published online 5 July) now show that the Q10 of ecosystem respiration is invariant with respect to mean annual temperat...
Research Interests: Geography, Environmental Science, Artificial Intelligence, Climate Change, Carbon Dioxide, and 15 morePhotosynthesis, Climate, Carbon Cycle, Medicine, Multidisciplinary, Atmospheric sciences, Atmosphere, Eddy Covariance, Plants, Changement Climatique, Ecosystem, Ecosystem Function, Oxygen Consumption, gross Primary Production, and Plant Leaves
Research Interests:
Measurements of the net CO2 flux between terrestrial ecosystems and the atmosphere using the eddy covariance technique have the potential to underpin our interpretation of regional CO2 source–sink patterns, CO2 flux responses to forcings,... more
Measurements of the net CO2 flux between terrestrial ecosystems and the atmosphere using the eddy covariance technique have the potential to underpin our interpretation of regional CO2 source–sink patterns, CO2 flux responses to forcings, and predictions of the future terrestrial C balance. Information contained in FLUXNET eddy covariance data has multiple uses for the development and application of global carbon models, including evaluation/validation, calibration, process parameterization, and data assimilation. This paper reviews examples of these uses, compares global estimates of the dynamics of the global carbon cycle, and suggests ways of improving the utility of such data for global carbon modelling.Net ecosystem exchange of CO2 (NEE) predicted by different terrestrial biosphere models compares favourably with FLUXNET observations at diurnal and seasonal timescales. However, complete model validation, particularly over the full annual cycle, requires information on the balan...
Research Interests:
Research Interests:
Research Interests:
... Viovy(1) (1) Laboratoire des Sciences du Climat et de l'Environnement, France (2) Institut National de Recherche Agronomique, Unité EMMAH, France aude ... analysis of the errors of a series of control runs and a sensitivity... more
... Viovy(1) (1) Laboratoire des Sciences du Climat et de l'Environnement, France (2) Institut National de Recherche Agronomique, Unité EMMAH, France aude ... analysis of the errors of a series of control runs and a sensitivity study have led to the selection of key parameters which ...
Research Interests:
This work presents a new dynamic global vegetation model designed as an extension of an existing surface‐vegetation‐atmosphere transfer scheme which is included in a coupled ocean‐atmosphere general circulation model. The new dynamic... more
This work presents a new dynamic global vegetation model designed as an extension of an existing surface‐vegetation‐atmosphere transfer scheme which is included in a coupled ocean‐atmosphere general circulation model. The new dynamic global vegetation model simulates the principal processes of the continental biosphere influencing the global carbon cycle (photosynthesis, autotrophic and heterotrophic respiration of plants and in soils, fire, etc.) as well as latent, sensible, and kinetic energy exchanges at the surface of soils and plants. As a dynamic vegetation model, it explicitly represents competitive processes such as light competition, sapling establishment, etc. It can thus be used in simulations for the study of feedbacks between transient climate and vegetation cover changes, but it can also be used with a prescribed vegetation distribution. The whole seasonal phenological cycle is prognostically calculated without any prescribed dates or use of satellite data. The model i...
Research Interests: Environmental Science, Geology, Geochemistry, Seasonality, Atmospheric sciences, and 12 moreBiosphere, Global Carbon Cycle, Global, Satellite Data, Kinetic Energy, Global Biogeochemical Cycles, Carbon Stock, Boolean Satisfiability, Surface Energy, Vegetation Cover, Model simulation, and Model Design
Research Interests:
Research Interests:
L'objet de l'etude est de decrire les methodes actuelles utilisees en teledetection pour etudier les evolutions spatiales et temporelles des couverts vegetaux. Les caracteristiques essentielles des donnees de teledetection, les... more
L'objet de l'etude est de decrire les methodes actuelles utilisees en teledetection pour etudier les evolutions spatiales et temporelles des couverts vegetaux. Les caracteristiques essentielles des donnees de teledetection, les proprietes optiques des feuilles de vegetaux, et enfin la definition de l'indice de vegetation et la description de son interet pour l'etude des productions vegetales par satellite sont abordees successivement
Research Interests:
Analyzing the causes and spatial pattern of the European 2003 carbon flux anomaly using seven models
Research Interests:
Research Interests:
Research Interests:
Research Interests: Environmental Science, Forestry, Climate Change, Carbon Dioxide, Carbon, and 15 moreBiomass, Plant Biology, Ecology, Carbon Sequestration, Modelling, Forest Ecology, Medicine, France, Computer Simulation, Forest Management, Carbon balance, Forestry Sciences, Greenhouse Effect, Ecosystem, and Oxford university
Research Interests:
Research Interests:
ABSTRACT Poster : EGU General Assembly .
Research Interests:
Research Interests: Physical Geography, Earth Sciences, Environmental Science, Climatology, Carbon, and 15 moreAtmospheric Modeling, Carbon Cycle, Biological Sciences, Environmental Sciences, Models, Biosphere, Atmosphere, Biogeosciences, Carbon balance, Primary Production, Ecosystem, Model Analysis, Interannual Variability, gross Primary Production, and Gas Exchange
Impact of climate variability and land use changes on global biogenic volatile organic compound emissions
Research Interests:
Abstract. Vegetation reconstructions from pollen data for the Last Glacial Maximum (LGM), 21 ky ago, reveal lan-scapes radically different from the modern ones, with, in particular, a massive regression of forested areas in both... more
Abstract. Vegetation reconstructions from pollen data for the Last Glacial Maximum (LGM), 21 ky ago, reveal lan-scapes radically different from the modern ones, with, in particular, a massive regression of forested areas in both hemispheres. Two main factors have to be taken into ac-count to explain these changes in comparison to today’s po-tential vegetation: a generally cooler and drier climate and a lower level of atmospheric CO2. In order to assess the relative impact of climate and atmospheric CO2 changes on the global vegetation, we simulate the potential mod-ern vegetation and the glacial vegetation with the dynami-cal global vegetation model ORCHIDEE, driven by outputs from the IPSL CM4 v1 atmosphere-ocean general circula-tion model, under modern or glacial CO2 levels for photo-synthesis. ORCHIDEE correctly reproduces the broad fea-
www.ann-geophys.net/31/633/2013/ doi:10.5194/angeo-31-633-2013 © Author(s) 2013. CC Attribution 3.0 License.
Research Interests:
This data set provides environmental data that have been standardized and aggregated for use as input to carbon cycle models at global (0.5-degree resolution) and regional (North America at 0.25-degree resolution) scales. The data were... more
This data set provides environmental data that have been standardized and aggregated for use as input to carbon cycle models at global (0.5-degree resolution) and regional (North America at 0.25-degree resolution) scales. The data were compiled from selected sources (Table 2) and integrated into gridded global and regional collections of climatology variables (precipitation, air temperature, air specific humidity, air relative humidity (NA only), pressure, downward longwave radiation, downward shortwave radiation, and wind speed), time-varying atmospheric CO2 concentrations, time-varying nitrogen deposition, biome fraction and type, land-use and land-cover change, C3/C4 grasses fractions, major crop distribution, phenology, multiple soil characteristics, and a land-water mask. The temporal ranges of the data are sufficient for carbon cycle model simulations from 1801 to 2010. These data were compiled specifically for the North American Carbon Program (NACP) Multi-Scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP) as the prescribed model input driver data (Huntzinger et al., 2013). The driver data were used by 22 terrestrial biosphere models to run baseline and sensitivity simulations. The standardized data provided consistent model inputs to minimize the inter-model variability caused by differences in environmental drivers and initial conditions. Together with the sensitivity simulations, the standardized input data enable better interpretation and quantification of structural and parameter uncertainties of model estimates. Data are provided in Climate and Forecast (CF) metadata convention compliant (version 1.4) netCDF-4 file formats. There are 3,152 *.nc4 data files with this data set.
Research Interests:
Research Interests:
Research Interests:
The Land Surface, Snow and Soil Moisture Model Intercomparison Project (LS3MIP) is designed to provide a comprehensive assessment of land surface, snow, and soil moisture feedbacks on climate variability and climate change, and to... more
The Land Surface, Snow and Soil Moisture Model Intercomparison Project (LS3MIP) is designed to provide a comprehensive assessment of land surface, snow, and soil moisture feedbacks on climate variability and climate change, and to diagnose systematic biases in the land modules of current Earth System Models (ESMs). The solid and liquid water stored at the land surface has a large influence on the regional climate, its variability and predictability, including effects on the energy, water and carbon cycles. Notably, snow and soil moisture affect surface radiation and flux partitioning properties, moisture storage and land surface memory. They both strongly affect atmospheric conditions, in particular surface air temperature and precipitation, but also large-scale circulation patterns. However, models show divergent responses and representations of these feedbacks as well as systematic biases in the underlying processes. LS3MIP will provide the means to quantify the associated uncerta...
Research Interests:
Research Interests:
Research Interests:
We present a new dynamical global vegetation model principally designed to be included in atmospheric general circulation models (AGCMs) or regional climate models. The model consists of a surface-vegetation-atmosphere transfer scheme... more
We present a new dynamical global vegetation model principally designed to be included in atmospheric general circulation models (AGCMs) or regional climate models. The model consists of a surface-vegetation-atmosphere transfer scheme coupled to a dynamical global vegetation model. It therefore simulates the principal processes of the continental biosphere influencing the global carbon cycle (photosynthesis, autotrophic and heterotrophic respiration of plants
Research Interests:
Research Interests:
ABSTRACT Sugarcane is currently the most efficient bioenergy crop with regards to the energy produced per hectare. With approximately half the global bioethanol production in 2005, and a devoted land area expected to expand globally in... more
ABSTRACT Sugarcane is currently the most efficient bioenergy crop with regards to the energy produced per hectare. With approximately half the global bioethanol production in 2005, and a devoted land area expected to expand globally in the years to come, sugar cane is at the heart of the biofuel debate. Dynamic global vegetation models coupled with agronomical models are powerful and novel tools to tackle many of the environmental issues related to biofuels if they are carefully calibrated and validated against field observations. Here we adapt the agro-terrestrial model ORCHIDEE-STICS for sugar cane simulations. Observation data of LAI are used to evaluate the sensitivity of the model to parameters of nitrogen absorption and phenology, which are calibrated in a systematic way for six sites in Australia and La Reunion. We find that the optimal set of parameters is highly dependent on the sites' characteristics and that the model can reproduce satisfactorily the evolution of LAI. This careful calibration of ORCHIDEE-STICS for sugar cane biomass production for different locations and technical itineraries provides a strong basis for further analysis of the impacts of bioenergy-related land use change on carbon cycle budgets. As a next step, a sensitivity analysis is carried out to estimate the uncertainty of the model in biomass and carbon flux simulation due to its parameterization.
Research Interests:
ABSTRACT We present a theoretical analysis of the net land-to-atmosphere CO2 flux, so as to discuss possible definitions of "emissions from land-use change" at global scale. Our work is based on the fact that the... more
ABSTRACT We present a theoretical analysis of the net land-to-atmosphere CO2 flux, so as to discuss possible definitions of "emissions from land-use change" at global scale. Our work is based on the fact that the terrestrial carbon cycle is affected by two anthropogenic perturbations. The first is the perturbation of the global Carbon-Climate-Nitrogen (CCN) system as observed with elevated CO2, climate change and increased nitrogen deposition; it impacts the intensive parameters of the terrestrial biosphere. The second is the Land-Use and Land-Use Change (LUC) perturbation induced by human activities; impacting the extensive parameters of the biosphere. Previous global carbon budgets tried to separate these two perturbations by defining two CO2 fluxes: the emissions from land-use change (LUC perturbation) and the land sink (CCN perturbation). Here, through successive mathematical demonstrations, we isolate four (not two) generic components of the net land-to-atmosphere CO2 flux. The two first components are the fluxes that would be observed if only one perturbation occurred. The two other components are due to the coupling of the CCN and LUC perturbations, highlighting the non-linear behavior of the terrestrial carbon cycle. Thanks to this, we introduce three possible definitions of "emissions from land-use change", that are indeed used in the scientific literature (often without clear distinctions), and we draw conclusions as for their absolute and relative behaviors. Finally, we illustrate our theoretical results thanks to two models: a simple carbon-climate model using a book-keeping module to estimate emissions from land-use change (named OSCAR), and the spatialized land-surface model ORCHIDEE. Our preliminary results show that comparing results from studies that do not use the same definition can lead to a bias of up to 20% between estimates of "emissions from land-use change". This makes our study of major interest to reconcile modeling and observation of "emissions from land-use change", and ultimately to distinguish direct and indirect effects of anthropogenic activities.
Research Interests:
Parameters-related uncertainty in modeling sugar cane yield with an agro-Land Surface Model. American Geophysical Union Fall Meeting (AGU 2013
Research Interests: Sugar cane and Cane
International audienc