[Company Details:]  

ONERA-DOTA laboratory,
...,
URL: http://www.onera.fr/, e-Mail:  

[Job Details:]

Context

This subject is part of a research program which deals with emerging questions such as sustainable cities, and particularly the adaptation of cities to climate change. The project, named ACCLIMAT (Adaptation au Changement Climatique de l’Agglomération Toulousaine), is founded by the foundation of scientific cooperation STAE. It aims at studying the interactions between several processes such as urban development, urban microclimate and climate change in the Toulouse area. It is based on the development of an interdisciplinary platform of numerical models. Such a tool aims at helping synthesis working out as it includes various themes from the socio-economic processes that determine the urban expansion to the spacialization of urban development.

This study requires uppermost the development of a new physical model and the estimation of the optical properties of representative urban materials at different scales. Such information is necessary for urban remote sensing studies or urban micro climate changes studies.

This program, strongly interdisciplinary, implies economists, architects, construction industry experts, geographers and climate experts.

Subject Description

This work aims at simulating the optical properties at different scales (from the street scale to the district scale) on the basis of an accurate description of the scene. Two main steps will be achieved: the development of an aggregation model and the simulation of the properties at larger scale.

Thus, in the first step, an aggregation model will be developed to estimate the optical properties at the street scale or the district scale from an accurate knowledge of the optical properties (spectral reflectance) of the elementary materials composing the landscape. The geometry is supposed to be known. The resulting radiative parameters and the corresponding hypotheses will be assessed using the 3D radiative transfer developed in our laboratory to study the urban area at very high spatial resolution. The following phenomena will be considered: radiative coupling between walls of buildings, shadowing, slope effect of the roofs, intra-class variability and directional behaviour of materials. The model will be validated using data acquired over Toulouse during two experiments: Capitoul, 2002, and Musarde, 2009.

Then, this model will be applied at several scales (street, district…) with various conditions (atmosphere, viewing geometry) to evaluate the impact of the scale on the determination of the optical properties.

To this end, the spectral reflectances will be measured using ONERA-DOTA facilities. The two following matters will be particularly analyzed:
• Evaluation of the intra-class variability of materials like tile, brick, cement, asphalt… which have an important variability (>20%) that depends on their use, exposure…To this purpose, in situ measurements will be achieved using ASD spectroradiometers.
• Measurement of the directional effects of materials of very reflective materials like glass, metals. This will be done using our spectral goniometers (MELOPEE and REMUSA bench).

These measurements will be registered in our MEMOIRES data base.

The candidate will work in a strongly interdisciplinary team. The results of the work will be published.

Practical Modalities

The candidate will work at Toulouse, in ONERA-DOTA laboratory (http://www.onera.fr/). He will use the existing facilities and simulation tools to conduct his work.

The candidate will be recruited by the "Fondation de Coopération scientifique STAE". The following criteria need to be fulfilled:

- One publication in an international review par year after its PhD.

- The candidate must have done his PhD outside the Midi Pyrenees area. If the candidate graduated in the Toulouse area, he must have worked during at least one year outside the Toulouse area.

Beginning: 1st September / 1st October 2010

Duration: 12 months

Required skills

- Physics of the measurement, radiative transfer in the Earth-Atmosphere system
- Strong ability to work in an interdisciplinary team
- Ability to write international scientific articles

For more informations, please contact:

Xavier Briottet
Research Director at ONERA
Xavier.Briottet@onera.fr
+33 5 62 25 26 05

or 

Bénédicte Diez
Research Engineer at ONERA
Benedicte.Diez@onera.fr
+33 5 62 25 28 84

[Contact Person:]

Xavier Briottet,
Tel: +33 5 62 25 26 05,
e-Mail: Xavier.Briottet@onera.fr