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Accueil > Emplois, Stages, Thèses > Bourses de thèses - financement acquis

PhD proposal : Pollution in the Grenoble valley : a weather-type approach

Laboratoire d’accueil : LEGI (UMR 5519)

Duration : 3 years, from 1st October 2018

Profile of the candidate : the candidate should have a good knowledge of atmospheric dynamics and experience in computer programming. Knowledge of standard statistical tools would be a plus. He/she should also have a good knowledge of English and, if possible, of French as well.

Advisors : Chantal STAQUET, LEGI and University Grenoble Alpes - Charles CHEMEL, University of Hertfordshire, UK

Contact : Chantal.Staquet(A) / +33 4 76 82 50 24

PhD work

- 1. Background and motivations

Urban air pollution is a major health issue. Most of the health effects are currently attributed to fine particles with a diameter less than 2.5 μm, or PM2.5. In Grenoble the yearly concentration distribution of PM2.5 estimated from dispersion models calibrated with actual measurements was in the 17 - 20 μg/m 3 range (2012 estimates), no threshold existing below which pollution has no health effect (WHO 2013).

This thesis work is part of the interdisciplinary MobilAir project on air pollution in Grenoble. MobilAir’s objectives are to propose novel methods for measuring and estimating pollution, to determine its impact on prenatal health and to understand the obstacles to changing modes of travel (or mobility) by inhabitants that would reduce pollution.

- 2. From PM2.5 emission to concentration : the key role of meteorology

Population exposure to PM2.5 depends on the local concentration of particles. Moreover, as epidemiological studies showed it, the impact on health is much more influenced by long-term PM2.5 concentrations, of the order of the year, than by specific episodes of high pollution (Report of the High Council of Public Health, 2012).

Estimating the health impact of PM2.5 therefore requires the knowledge of PM concentration field on a local scale, ideally at street level, and over a long period.

This concentration field depends on PM2.5 emissions and meteorology. Like concentration, of which it is the driver, meteorology must be modelled on a fine spatial scale and over a long period of time.

However, even at a horizontal scale of 100 m, current computer capacities do not allow the computation of meteorological fields to be carried out beyond a time window of a week. A new approach has therefore to be designed for a computation over a year to be carried out, from which the concentration fields can be calculated and population exposure estimated. This is the core of the PhD work.

- 3. Thesis work

This approach relies on identifying the types of weather over the Grenoble valley, from a classification obtained from standard statistical tools. Such weather types could for example include “wintertime anticyclonic regime”. Statistical classification tools are to be used at this step. For each weather type, the meteorological fields will be modeled numerically over a few days, which is generally the duration of the weather type ; the WRF (Weather Research and Forecast) three-dimensional community model will be used for this purpose. The validity of the meteorological fields thus obtained numerically for each weather type should be evaluated in relation with wind and temperature measurements in the Grenoble valley. A detailed analysis of these fields can then be carried out, involving the identification of "ventilation" zones and of "stagnation" zones within which pollution emissions should be avoided.

The computation of the meteorological fields will allow that of the PM concentration field using the emission inventory prepared by the air quality agency of the Auvergne Rhône-Alpes region, which will be implemented in the numerical model WRF. The calculation of these concentration fields will make it possible to estimate the most critical areas from the point of view of air quality, which will depend on the weather type considered and on which effort should be focused in a pollution reduction policy.

In collaboration with the air quality agency of Région Auvergne Rhône-Alpes (Atmo AuRA) and MobilAir’s researchers, the thesis work will also allow to refine the knowledge of the population exposure to PM2.5 at an even smaller scale, about 10 m.

- 4. In the longer term

If time permits, the approach followed during the thesis will be implemented in the context of climate change, to estimate the concentration fields in the Grenoble urban area in 2050 for various emission scenarios.