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Preparation of the TRISHNA satellite mission (https://trishna.cnes.fr/en), dedicated to the observation of terrestrial surfaces in the thermal infrared domain.
To provide a soil-vegetation-atmosphere transfer model (SVAT) that simulates the 3D temperature in the canopy, so as to simulate TRISHNA measurements of plant cover (forest, crop,..) with topography, atmosphere and any instrumental configuration (i.e., spatial / spectral resolution,…).
Most of the many SVAT models that simulate the radiative transfer, the energy balance and the functioning of vegetation cover employ very simplifying assumptions to represent vegetation cover. Thus, the three-dimensional (3D) architecture of canopies is generally represented by a turbid medium distributed in layers or schematic geometric objects (e.g., ellipsoids). Consequently, the developed model called DART-EB, will be based on the DART model (https://dart.omp.eu) to create the 3D landscapes and on its new DART-Lux mode to simulate the 3D radiative balance and the remote sensing images. DART-EB will therefore simulate the radiative transfer and the main surface processes involved in the energy balance (convective fluxes and photosynthetic activity in the canopy, heat fluxes in the soil, etc.). It will operate on landscapes of kilometer dimension through the combination of 3D (e.g., radiation) and 1D (e.g., 1D wind profile in the canopy) models already validated.
Two parallel approaches will be carried out. (1) Redevelopment of the DART-EB model (Belot, 2007) which iteratively combines several models: radiation (very old version of DART), foliar photosynthesis (Collatz, 1991), turbulent exchanges (i.e., temperature, humidity and CO2 concentration) determined by « Localized Near Field Theory » (Raupach, 1989), and heat and mass exchanges at ground level derived from a diffusive approach such as ISBA-df. (2) Implementation in a 3D architecture of modeling in the 1D SCOPE energy balance model (Van der Tol et al., 2009, Van der Tol et al., 2016, https://scope-model.readthedocs.io/ in / latest). SCOPE is a reference for simulating TRISHNA measurements. Its major limitation is that it neglects the cover architecture: it represents the cover as a stack of turbid layers, and therefore neglects the 2D distribution which plays a greater role than the 1D distribution (Regaieg et. al., 2021).
The validation of SCOPE will be carried out with 2 complementary approaches. (1) SCOPE model: validation will only be carried out with turbid multi-layer covers that SCOPE can simulate. (2) Measurements on experimental sites of CESBIO and of National Science Foundation’s National Ecological Observatory Network (NEON), within the framework of a collaboration with NASA (T. Yin).
The first 7 months of work will be devoted to the analysis of the DART-EB 2007 and SCOPE models, followed by the implementation of all or part of their modules in DART-EB. DART-EB 2007 is detailed in a PhD manuscript. It offers the advantage of having already been implemented. SCOPE is provided as a Matlab code. It offers the advantage of being a reference model and to ease the validation work. The 2 modeling will be implemented in DART-EB. After the necessary debugging tests, the following 5 months will be devoted to the validation of DART-EB with SCOPE and the experimental measurements.
- Knowledge of the physics of vegetation functioning (turbulent fluxes, photosynthesis, etc.)
- Good Python programming skills, and if possible Matlab
- Ability to work in a team, with the team that develops DART
- Autonomy and initiative to achieve the objectives from the codes and documents provided
CESBIO, Toulouse (https://www.cesbio.cnrs.fr/), France
Up to 2616€, according to experience
1 year, possibly renewable, starting in September – October 2021.
Gastellu-Etchegorry J.P., email@example.com