HAL Id: hal-02814992
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High resolution surface temperature and urban thermal anisotropy simulations : validation by airborne remote
sensing data from the CAPITOUL experiment
Aurélien Hénon, Jean-Pierre Lagouarde, Patrice Mestayer, Dominique Groleau
To cite this version:
Aurélien Hénon, Jean-Pierre Lagouarde, Patrice Mestayer, Dominique Groleau. High resolution sur- face temperature and urban thermal anisotropy simulations : validation by airborne remote sensing data from the CAPITOUL experiment. American Meteorological Society 89th Annual Meeting / 8th Symposium an the Urban Environment, Jan 2009, Phoenix, United States. 1 p., 2009. �hal-02814992�
High resolution surface temperature and urban thermal
anisotropy simulations: validation against airborne remote sensing TIR data over Toulouse city (France).
Aurélien Hénon
1, Jean-Pierre Lagouarde
2, Patrice Mestayer
1, Dominique Groleau
3.
1 1 1
1 Laboratoire de MLaboratoire de MLaboratoire de MLaboratoire de Méééécanique des Fluides, Institut de Recherche en Sciences et Technicanique des Fluides, Institut de Recherche en Sciences et Technicanique des Fluides, Institut de Recherche en Sciences et Technicanique des Fluides, Institut de Recherche en Sciences et Techniques de la Ville, CNRS, ques de la Ville, CNRS, ques de la Ville, CNRS, Ecoleques de la Ville, CNRS, EcoleEcoleEcole Centrale de Nantes, France ;
Centrale de Nantes, France ; Centrale de Nantes, France ; Centrale de Nantes, France ;
2 2 2
2 INRA, UR1263 EPHYSE,INRA, UR1263 EPHYSE,VillenaveINRA, UR1263 EPHYSE,INRA, UR1263 EPHYSE,VillenaveVillenaveVillenave d'd'd'd'OrnonOrnonOrnonOrnon, , , , FranceFranceFranceFrance
3 3
3 3 CERMA, UMR CNRS 1563, ENSA NantesCERMA, UMR CNRS 1563, ENSA NantesCERMA, UMR CNRS 1563, ENSA NantesCERMA, UMR CNRS 1563, ENSA Nantes
AMS 89th Annual Meeting 11-15 January 2009
Phoenix, AZ
8
thSymposium on the Urban Environment
The heterogeneity of the local surface temperatures over an urban area, due to the geometrical complexity of the canopy and to the diversity of the
thermal properties of the different materials, generates strong thermal anisotropy effects at the district scale. Airborne thermal infrared measurements obtained over Toulouse (France) during the CAPITOUL experiment (http://medias.cnrs.fr/capitoul/) have been analyzed in view of developing an
approach to correct TIR satellite remote sensing from the canopy-generated anisotropy. Both of the two presented studies are based on the SOLENE
software. SOLENE simulates the air-solid thermo-radiative transfers coupled with the visible and thermal infrared radiative transfers. Parameterizations of thermal inertia and heat exchange through walls are also modelled, with several layers. The computations are made with fine meshes (≈ 1 m²) over all the facets of the urban canopy described by a 3D model. The inputs are the meteorological data and the simulations are performed with a 15 minutes time step over periods long enough to ensure representative thermal regimes.
Layer Thermal Model
SOLENE model
Radiative Transfer Model
Input Data
Urban fragment
(18 000 m², 1 m resolution)
High resolution brightness temperature (February 25th 2005, 13h53)
Simulation results Airborne FLIR
camera measurements
Type of
surface Layer Material Thickness (m)
Thermal Conductivity
(W m-1 K-1)
Thermal Capacity (106 J m-3 K-1)
Albedo Emissivity
tile 1 Tile 0.06 1.15 1.58 0.15 0.90
2 Wood 0.03 0.2 2.20
wall 1 Red Brick 0.06 1.15 1.58 0.25 0.92
2 Red Brick 0.24 1.15 1.58
street 1 Tar 0.05 0.82 1.74 0.08 0.95
2 Stone
Aggregate 0.2 2.1 2.0
Meteorological Data
Thermal properties
0 100 200 300 400 500 600 700
0 2 4 6 8 10 12 14 16 18 20 22 24 Hour
Flux (W/m²)
-5 0 5 10
Temperature (°C)
Downward short wave (W/m²) Downward long wave (W/m²) Air Temperature (°C)
Pixel-by-pixel comparison between the results from the
SOLENE model and the airborne FLIR camera data from the CAPITOUL experiment : satisfactory in general, without
microscale variability (small items are not modelled)
Evaluation and optimization of the thermal model/parameters of the urban district
Averaged street canyon geometry (5 000 rectangular 1-m² facets)
SOLENE model
- 18 different street
orientations by 10° steps
- Simulation of the facet brightness temperatures
3-D model of the urban test
area (~3 km²)
- Estimation of the viewed ratio of each class (Aij) using the POVRAY software and the 3-D model, for different viewing directions.
Airborne FLIR camera measurements Simulation results
Thermal anisotropy (K) integrated over the 3 km² urban test area (July 15th 2004, 11h15-11h49)
JP3.2
Simulation of a district
Directional anisotropy at the city scale
- Integration of the simulated temperature profiles for
different viewing positions
- Determination of directional temperatures for 6 different
classes of surfaces (Tb,ij) : roofs, walls and grounds, sunlit and shaded.
Conclusions
The angular distribution of the directional temperature anisotropy is quite well reproduced by the simulations, especially the hot spot.
But the anisotropy values (differences between off-nadir and nadir brightness temperatures) are still under-evaluated.
Improvements in the modelling of anisotropy can be expected from a better assessment of surface characteristics (thermo-radiative parameters) at the
district scale and from a finer geometry resolution.
The representation by an unique, averaged street-canyon is relevant only to rather uniform districts.
This method provides the directional TIR anisotropy averaged at scales between a few hundred meters and a few kilometres. It seems well adapted for interpreting remotely sensed data from large swath spatial sensors.
-Representation of the resulting directional brightness temperature and thermal anisotropy at the district scale
- Comparison against the thermal anisotropy obtained from the airborne FLIR camera data (8 oriented flights)
