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Team 1 : Functioning of vegetated surfaces modeling and remote sensing of continental surfaces




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Head : Jean-Philippe Gastellu-Etchegorry

Objectives and framework of research

This is to develop and improve models that describe the process of exchanging energy and matter at the interface Soil - Vegetation - Atmosphere. and simulate remote sensing measurements.

These modeling work based on the collaboration of research areas in physics, ecology, and collaboration with CESBIO projects and preparation of space missions. On the other hand, approaches (eg, modeling "nested", "integrated" and "shared") promote synergy within the team and more broadly with the scientific community.

Key words: modeling, radiative transfer (DART), hydrological models and operating models
(SEVE, SAMIR, ICASTICS, SAFY). (SEVE, SAMIR ICASTICS, SAFY).
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Powered by measures (eg, brightness temperatures, mass balance and energy) from the SouthWest and SudMed sites, and the remote sensing data, models are well adapted tools for monitoring and environmental management . This is important in the context of anthropogenic climate change.

Because of its ability to observe the Earth (synoptic and repetitive), remote sensing is also an important research topic in modeling. It is indeed a unique tool to run functioning models of the surfaces with spatial information at different scales of time and space, via the inversion of measurements with the aid of radiative transfer models or through the direct assimilation of satellite measurements into models of functioning of landscapes.

The models (simulation of landscapes and / or physical and biological processes involved)are based primarily on "mechanistic" approaches which depends on the complexity of these processes and the structure of landscapes. Thus, it will be one-dimensional (1D), two-dimensional (2D) or three-dimensional (3D) depending on the objectives and environments studied.

Two types of modeling are developed and implemented. (1) radiative transfer modeling to simulate remote sensing data and radiation budget.(2) an integrated modeling of all processes (water flow, photosynthesis, etc..), Which determine the functioning of land surfaces. A key point is that the two modeling approaches are complementary. The heterogeneity of the environment is a major constraint. It affects all approaches.

  • Modeling and remote sensing measurements of radiation balance

This modeling work concerns in particular the themes of "Very High Resolution", "Thermal Infrared", "Hyperspectral" and "Multitemporal. It contributes to the operational workings of CESBIO well as the preparation of future space missions controlled from CESBIO ( SMOS , VENμS-GMES , BIOMASS ) and other missions in which collaborates CESBIO (MISTIGRI).

  • Functioning of vegetated surfaces modeling

To solve the problems related to the ecosystem heterogeneity, for instance the presence of strong discontinuities (topography, agricultural plot ,...), several types of models are developed, taking into account different spatial and temporal scales of the studied processes.

Local Scale (1D)
Because of the lack of mechanistic crop model able to simulate the various components of water and carbon fluxes, a process-oriented model is developed. It is adapted to the ecosystems of our study areas (agroecosystem). It aims to replicate and predict the ecosystem response (growth, feed water, C...) to the climatic and anthropogenic constraints. It is based on in situ observations of the Southwest and SudMed projects.

Regional Scale (2D or multi-1D)
The originality of the approach lies mainly on the coupling "Remote sensing multi-resolution (spatial and temporal) - Modeling," with

  • Inversion of satellite measurements in order to obtain biophysical parameters with remote sensing models.
  • Assimilation of satellite measurements into functioning models.
  • Change of spatial scales: aggregation and disaggregation of remote sensing data.

These SVAT models (Soil Vegetation Atmosphere Transfer) , radiative transfer, water balance and carbon functioning of vegetation) are more or less complex depending on the accepted compromise between "Research" and "Applications"

Intermediate Scale (3D)
Two types of 3D modeling are being studyed :

  • SEVE Model : surface scheme that incorporates and relies the major processes contributing to the functioning of the surfaces. The very broad scales of time and space of the involved processes is a very strong constraint.
  • DARTEB Model : we want to build a model of energy balance and fluxes as efficient and robust as the DART model . In addition, DARTEB is developed to be integrated in the SEVE model

Integrated 3D Modeling

 

1D/2D Modeling of vertical transfers

DART : Radiative Transfer and Remote Sensing

 

ICASTiCS, ICARE : parcel scale

DARTEB : Energy balance and fluxes

 

SAFY, SAMIR : regional scale and remote sensing coupling

 

SEVE : Radiative Transfer, hydrology and energy balance.

 

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aerial dry biomass production

coupling :

  • Formosat-2 Images
    ( foliar index LAI)
  • SAFY model

     
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