A5044613043- Atmospheric and Environmental Gas Dynamics
- Remote Sensing in Agriculture
- Plant Water Relations and Carbon Dynamics
- Climate variability and models
- Hydrology and Watershed Management Studies
- Atmospheric Ozone and Climate
- Meteorological Phenomena and Simulations
- Remote Sensing and LiDAR Applications
- Urban Heat Island Mitigation
- Leaf Properties and Growth Measurement
- Atmospheric aerosols and clouds
- Cryospheric studies and observations
- Species Distribution and Climate Change
- Plant responses to elevated CO2
- Forest ecology and management
- Atmospheric chemistry and aerosols
- Tree-ring climate responses
- Calibration and Measurement Techniques
- Geophysics and Gravity Measurements
- Land Use and Ecosystem Services
- Soil Geostatistics and Mapping
- Remote Sensing and Land Use
- Forest Management and Policy
- Reservoir Engineering and Simulation Methods
- Global Energy and Sustainability Research
Laboratoire des Sciences du Climat et de l'Environnement
2009-2024
Université Paris-Saclay
2022-2023
CEA Paris-Saclay
2022-2023
Centre National de la Recherche Scientifique
2006-2023
Noveltis (France)
2014-2023
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2006-2023
Université de Versailles Saint-Quentin-en-Yvelines
2006-2023
Département Environnement et Agronomie
2004-2006
EMMAH - Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes
2004
Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement
2002-2004
Abstract. Land models, which have been developed by the modeling community in past few decades to predict future states of ecosystems and climate, be critically evaluated for their performance skills simulating ecosystem responses feedback climate change. Benchmarking is an emerging procedure measure models against a set defined standards. This paper proposes benchmarking framework evaluation land model performances and, meanwhile, highlights major challenges at this infant stage benchmark...
This study investigates the representativeness of land cover and leaf area index (LAI) sampled by a global network sites to be used for evaluation biophysical products, such as LAI or fAPAR, derived from current satellite systems. The networks considered include 100 where ground measurements fAPAR have been performed validation medium resolution 188 FLUXNET 52 AERONET sites. All retained had less than 25% water bodies within 8times8 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Abstract. Assimilation of in situ and satellite data mechanistic terrestrial ecosystem models helps to constrain critical model parameters reduce uncertainties the simulated energy, water carbon fluxes. So far assimilation eddy covariance measurements from flux-tower sites has been conducted mostly for individual ("single-site" optimization). Here we develop a variational system optimize 21 ORCHIDEE biogeochemical model, using net CO2 flux (NEE) latent heat (LE) 12 temperate deciduous...
Abstract Accurate terrestrial biosphere model (TBM) simulations of gross carbon uptake (gross primary productivity – GPP) are essential for reliable future sink projections. However, uncertainties in TBM GPP estimates remain. Newly-available satellite-derived sun-induced chlorophyll fluorescence (SIF) data offer a promising direction addressing this issue by constraining regional-to-global scale modelled GPP. Here, we use monthly 0.5° GOME-2 SIF from 2007 to 2011 optimise parameters the...
Abstract. Large uncertainties in land surface models (LSMs) simulations still arise from inaccurate forcing, poor description of heterogeneity (soil and vegetation properties), incorrect model parameter values incomplete representation biogeochemical processes. The recent increase the number type carbon cycle-related observations, including both situ remote sensing measurements, has opened a new road to optimize parameters via robust statistical model–data integration techniques, order...
Abstract. Correct representation of seasonal leaf dynamics is crucial for terrestrial biosphere models (TBMs), but many such cannot accurately reproduce observations onset and senescence. Here we optimised the phenology-related parameters ORCHIDEE TBM using satellite-derived Normalized Difference Vegetation Index data (MODIS NDVI v5) that are linearly related to model fAPAR. We found misfit between decreased after optimisation all boreal temperate deciduous plant functional types, primarily...
Abstract. The first satellite-based global retrievals of terrestrial sun-induced chlorophyll fluorescence (SIF) were achieved in 2011. Since then, a number SIF datasets with different spectral, spatial, and temporal sampling characteristics have become available to the scientific community. These been useful monitor dynamics productivity range vegetated areas worldwide, but coarse spatiotemporal low signal-to-noise ratio data hamper their application over small or fragmented ecosystems....
Abstract Predicting terrestrial carbon, C, budgets and carbon‐climate feedbacks strongly relies on our ability to accurately model interactions between vegetation, C water cycles, the atmosphere. However, fluxes simulated by global, process‐based biosphere models (TBMs) remain subject large uncertainties, partly due unknown or poorly calibrated parameters. This is because TBMs have not routinely been confronted against cycle related datasets within a statistical data assimilation (DA)...
The community involved in modeling radiation transfer over terrestrial surfaces designed and implemented the first phase of a model intercomparison (RAMI) exercise. This paper discusses rationale motivation for this endeavor, presents protocol as well evaluation procedures, describes principal results. Participants were asked to simulate variety precisely defined environments illumination conditions. These abstractions typical systems included both homogeneous heterogeneous scenes....
[1] In some regions of the Amazon, global biogeophysical models have difficulties in reproducing measured seasonal patterns net ecosystem exchange (NEE) carbon dioxide. The process-based biosphere model Organizing Carbon and Hydrology Dynamic Ecosystems (ORCHIDEE) used this study showed that a standard parameterization produces NEE are opposite phase to eddy flux data tropical evergreen forest at Tapajós km 67 site (Brazil), like many other models. However, we optimized several key...
Abstract Over the last few years, solar‐induced chlorophyll fluorescence (SIF) observations from space have emerged as a promising resource for evaluating spatio‐temporal distribution of gross primary productivity (GPP) simulated by global terrestrial biosphere models. SIF can be used to improve GPP simulations optimizing critical model parameters through statistical Bayesian data assimilation techniques. A prerequisite is availability functional link between and in Here we present...
Abstract. Carbonyl sulfide (COS), a trace gas showing striking similarity to CO2 in terms of biochemical diffusion pathway into leaves, has been recognized as promising indicator the plant gross primary production (GPP), amount carbon dioxide that is absorbed through photosynthesis by terrestrial ecosystems. However, large uncertainties about other components its atmospheric budget prevent us from directly relating COS measurements GPP. The largest uncertainty comes closure budget, with...
Spectral indices from remotely sensed data, such as the Normalized Difference Vegetation Index (NDVI), are often used to estimate biophysical characteristics of vegetation. The objective this study is evaluate effect senescent leaves on estimation fraction photosynthetically active radiation absorbed by green elements canopy (fAPAR g ) NDVI measurements. An experiment was conducted under controlled conditions over grass canopies. Both and fAPAR were measured when cover changed. results...
Abstract We investigate the benefits of assimilating in situ and satellite data fraction photosynthetically active radiation (FAPAR) relative to eddy covariance flux measurements for optimization parameters ORCHIDEE (Organizing Carbon Hydrology Dynamic Ecosystem) biosphere model. focus on model related carbon fixation, respiration, phenology. The study relies two sites—Fontainebleau (deciduous broadleaf forest) Puechabon (Mediterranean evergreen forest)—where net exchange (NEE) latent heat...
In-flight assessment of the radiometric performances space-borne instruments can be achieved by means vicarious calibration over Pseudo-Invariant Calibration Sites (PICS). PICS are chosen for high temporal stability their surface optical properties combined with a spatial homogeneity. A first list main desert PIC sites was identified 20 years ago medium/coarse resolution in solar spectral range (400–2500 nm). They located Saharan and Arabian Peninsula. Six them have since been endorsed...
Abstract. Land surface models (LSMs), which form the land component of earth system models, rely on numerous processes for describing carbon, water and energy budgets, often associated with highly uncertain parameters. Data assimilation (DA) is a useful approach optimising most critical parameters in order to improve model accuracy refine future climate predictions. In this study, we compare two different DA methods seven plant functional types (PFTs) ORCHIDEE LSM using daily averaged...
Abstract Space‐borne retrievals of solar‐induced chlorophyll fluorescence (SIF) over land surfaces have recently become a resource for studying and quantifying the broad scale dynamics gross carbon uptake (gross primary productivity—GPP) across ecosystems. To prepare assimilation SIF data in terrestrial biosphere models, we examine how differences between products (due to acquisition characteristics processing chain) may affect optimization model parameters resultant GPP estimate. We compare...