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PhD Defense


Title : High-resolution modelling of long-range pollution transport

Date and time : The 19-01-2012 at 14h00

Type : thèse

Université qui délivre le diplôme : Université Pierre et Marie Curie

Location : UPMC - 4, place Jussieu - 75005 Paris - Salle Gobi, tour 46-56, 2ème étage
Members of jury :


- Mme Laurence PICON

- Mr Steve ARNOLD, rapporteur

- Mr Jean-Luc ATTIE, rapporteur

- Mme Elsa REAL, examinatrice

- Mr Bernard LEGRAS, examinateur

- Mme Kathy LAW, Directrice de thèse

- Mr François RAVETTA, directeur de thèse

Summary :


Air pollution can be transported between continents by large-scale atmospheric dynamics, where it can impact climate and regional air quality far from emission regions. During transport, concentrations in polluted plumes are affected by mixing with the background. Impacts of long-range pollution on climate and air quality are usually quantified using global Eulerian models, that tend to overestimate mixing due to their low resolution. This induces errors in the simulated export of pollutants, and in the reaction rates due to the non-linearity of atmospheric chemistry.


This thesis aims to better understand and quantify mixing of pollutant plumes in the free troposphere during long-range transport, and its representation in numerical models. It focuses on the Arctic, which is a region vulnerable to climate change, and where greenhouse gases and aerosol distributions are strongly influenced by transport of pollution from mid-latitudes. The work focuses on three case studies of transport into the Arctic troposphere during the POLARCAT campaign, in summer 2008.


Results include estimates of the intensity of mixing in the Arctic troposphere, which was found to be lower than in mid-latitudes. The results also show that a Lagrangian modelling approach is able to reproduce the variability in observed concentrations in aged plumes, to simulate the transport of small-scale structures, and to evaluate the variability of ozone evolution in pollutant plumes due to differences in mixing scenarios. The model results are also used to assess pollutant transport simulated by global models in the Arctic, and to define the resolution neeeded for more accurate simulations. Overall, the results highlight the necessity to combine Lagrangian and Eulerian approaches to improve the representation of long-range pollution transport in numerical models.

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