Pierre Béziat
Centre national de la recherche scientifique
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Featured researches published by Pierre Béziat.
Bulletin of the American Meteorological Society | 2006
A. J. Dolman; J. Noilhan; P. Durand; C. Sarrat; A. Brut; B. Piguet; A. Butet; N. Jarosz; Y. Brunet; Denis Loustau; E. Lamaud; L. F. Tolk; R. Ronda; F. Miglietta; Beniamino Gioli; V. Magliulo; M. Esposito; Christoph Gerbig; S. Körner; P. Glademard; M. Ramonet; P. Ciais; B. Neininger; R. W. A. Hutjes; J.A. Elbers; R. Macatangay; O. Schrems; G. Pérez-Landa; M. J. Sanz; Y. Scholz
Quantification of sources and sinks of carbon at global and regional scales requires not only a good description of the land sources and sinks of carbon, but also of the synoptic and mesoscale meteorology. An experiment was performed in Les Landes, southwest France, during May?June 2005, to determine the variability in concentration gradients and fluxes of CO2. The CarboEurope Regional Experiment Strategy (CERES; see also http://carboregional.mediasfrance.org/index) aimed to produce aggregated estimates of the carbon balance of a region that can be meaningfully compared to those obtained from the smallest downscaled information of atmospheric measurements and continental-scale inversions. We deployed several aircraft to concentration sample the CO2 and fluxes over the whole area, while fixed stations observed the fluxes and concentrations at high accuracy. Several (mesoscale) meteorological modeling tools were used to plan the experiment and flight patterns. Results show that at regional scale the relation between profiles and fluxes is not obvious, and is strongly influenced by airmass history and mesoscale flow patterns. In particular, we show from an analysis of data for a single day that taking either the concentration at several locations as representative of local fluxes or taking the flux measurements at those sites as representative of larger regions would lead to incorrect conclusions about the distribution of sources and sinks of carbon. Joint consideration of the synoptic and regional flow, fluxes, and land surface is required for a correct interpretation. This calls for an experimental and modeling strategy that takes into account the large spatial gradients in concentrations and the variability in sources and sinks that arise from different land use types. We briefly describe how such an analysis can be performed and evaluate the usefulness of the data for planning of future networks or longer campaigns with reduced experimental efforts.
Journal of Applied Meteorology and Climatology | 2011
Olivier Merlin; Ahmad Al Bitar; Vincent Rivalland; Pierre Béziat; Eric Ceschia; Gérard Dedieu
Analytical expressions of evaporative efficiency over bare soil (defined as the ratio of actual to potential soil evaporation) have been limited to soil layers with a fixed depth and/or to specific atmospheric conditions. To fill the gap, a new analytical model is developed for arbitrary soil thicknesses and varying boundary layer conditions. The soil evaporative efficiency is written [0.5 – 0.5 cos(πθL/ θmax)]^P with θL being the water content in the soil layer of thickness L, θmax the soil moisture at saturation and P a function of L and potential soil evaporation. This formulation predicts soil evaporative efficiency in both energy-driven and moisture-driven conditions, which correspond to P 0.5 respectively. For P = 0.5, an equilibrium state is identified when retention forces in the soil compensate the evaporative demand above the soil surface. The approach is applied to in situ measurements of actual evaporation, potential evaporation and soil moisture at five different depths (5, 10, 30 and 60/100 cm) collected in summer at two sites in southwestern France. It is found that (i) soil evaporative efficiency cannot be considered as a function of soil moisture only, since it also depends on potential evaporation, (ii) retention forces in the soil increase in reaction to an increase of potential evaporation and (iii) the model is able to accurately predict soil evaporation process for soil layers with an arbitrary thickness up to 100 cm. This new model representation is expected to facilitate the coupling of land surface models with multi-sensor (multi-sensing-depth) remote sensing data.
Archive | 2012
Christine Moureaux; Eric Ceschia; Nicolas Arriga; Pierre Béziat; Werner Eugster; Werner L. Kutsch; Elizabeth Pattey
Croplands are managed ecosystems with rapid development over the course of the growing season under nearly optimal growth conditions with respect to nutrient availability (fertilization), water availability (possible irrigation in dry conditions), competition (monocultures where herbicide and fungicides applications keep other competitors off the plot) and plant health (insecticides minimize herbivory by insects).
Agricultural and Forest Meteorology | 2009
Pierre Béziat; Eric Ceschia; Gérard Dedieu
Agriculture, Ecosystems & Environment | 2010
Eric Ceschia; Pierre Béziat; Jean-François Dejoux; Marc Aubinet; Ch. Bernhofer; Bernard Bodson; Nina Buchmann; Arnaud Carrara; Pierre Cellier; P. Di Tommasi; J.A. Elbers; Werner Eugster; Thomas Grünwald; C.M.J. Jacobs; Wilma Jans; Michael Jones; Werner L. Kutsch; Gary Lanigan; E. Magliulo; Olivier Marloie; E.J. Moors; Christine Moureaux; Albert Olioso; Bruce Osborne; M. J. Sanz; Matthew Saunders; Pete Smith; H. Soegaard; Martin Wattenbach
Agriculture, Ecosystems & Environment | 2010
Pete Smith; Gary Lanigan; Werner L. Kutsch; Nina Buchmann; Werner Eugster; Marc Aubinet; Eric Ceschia; Pierre Béziat; Jagadeesh Yeluripati; Bruce Osborne; E.J. Moors; Aurore Brut; Martin Wattenbach; Matthew Saunders; Michael Jones
Agriculture, Ecosystems & Environment | 2010
Werner L. Kutsch; Marc Aubinet; Nina Buchmann; Pete Smith; Bruce Osborne; Werner Eugster; Martin Wattenbach; Marion Schrumpf; Ernst-Detlef Schulze; Enrico Tomelleri; Eric Ceschia; Christian Bernhofer; Pierre Béziat; Arnaud Carrara; P. Di Tommasi; Thomas Grünwald; Michael Jones; Vincenzo Magliulo; Olivier Marloie; Christine Moureaux; Albert Olioso; M. J. Sanz; Matthew Saunders; Henrik Søgaard; Waldemar Ziegler
Remote Sensing of Environment | 2012
Martin Claverie; V. Demarez; Benoît Duchemin; Olivier Hagolle; Danielle Ducrot; Claire Marais-Sicre; Jean-François Dejoux; Mireille Huc; Pascal Keravec; Pierre Béziat; Remy Fieuzal; Eric Ceschia; Gérard Dedieu
Agriculture, Ecosystems & Environment | 2010
E.J. Moors; C.M.J. Jacobs; Wilma Jans; Iwan Supit; Werner L. Kutsch; Christian Bernhofer; Pierre Béziat; Nina Buchmann; Arnaud Carrara; Eric Ceschia; J.A. Elbers; Werner Eugster; Bart Kruijt; Benjamin Loubet; E. Magliulo; Christine Moureaux; Albert Olioso; Matthew Saunders; Henrik Soegaard
Agriculture, Ecosystems & Environment | 2010
Werner Eugster; Antje M. Moffat; Eric Ceschia; Marc Aubinet; C. Ammann; Bruce Osborne; Phillip A. Davis; Pete Smith; C.M.J. Jacobs; E.J. Moors; Valérie Le Dantec; Pierre Béziat; Matthew Saunders; Wilma Jans; Thomas Grünwald; Corinna Rebmann; Werner L. Kutsch; Radek Czerný; Dalibor Janouš; Christine Moureaux; Delphine Dufranne; Arnaud Carrara; Vincenzo Magliulo; Paul Di Tommasi; Jørgen E. Olesen; Kirsten Schelde; Albert Olioso; Christian Bernhofer; Pierre Cellier; Eric Larmanou