Research Topics

Research activities at CEREA are concerned with the atmospheric environment, focusing on the micrometeorology of the atmospheric boundary layer (i.e., the atmospheric layer that extends from the surface to 1 or 2 km altitude) and the numerical modeling of air quality. The assimilation of data into geophysical models is also an important research area.

• Dynamics of the Atmospheric Boundary Layer
  CEREA scientists study the dynamics of the atmospheric boundary layer by means of meteorological measurements and numerical simulations. The instrumentation (sodars, surface meteorological stations, instrumented masts, sonic anemometers, UHF radar, wind lidar, diffusiometers, scintillometer) provide reliable and accurate measurements of wind, temperature, solar radiation, relative humidity and atmospheric turbulence. Those instruments are set up in part on the campus of École Polytechnique at Palaiseau, as part of a regional observatory for air quality and meteorology (SIRTA) of the Pierre-Simon Laplace Institute (IPSL). The atmospheric version of the Code_Saturne CFD model , which was developed at CEREA, provides a realistic description of atmospheric flow and heat transfer over spatial scales ranging from a few meters (for example, vehicle exhaust) to a few kilometers (urban area or industrial site). This model is in part evaluated with measurements obtained at SIRTA. Examples of ongoing applications include the dispersion of pollutants among buildings or near a roadway, the estimation of wind and turbulence fields at a wind energy site, and the estimation of heat transfer between buildings and the ambient atmosphere. In that respect, important partnerships have been created with the scientific and technical network for air issues (RST Air) of the Ministry of Ecology (MTES) and EDF Énergies Nouvelles (Renewable Energy Division of the French Energy Group EDF), respectively.
  
  
• Air Quality Modeling
  CEREA develops and applies its own air quality modeling system , Polyphemus , which is used for both research and applied studies. Polyphemus is central to many studies, such as future emission scenarios (for example, the effect of new fuels on air quality), impact studies for industrial emissions and new roadways, regional air quality forecasting, radionuclide dispersion following accidental releases, and transboundary pollution at the continental scale (mercury and other heavy metals, persistent organic pollutants, acid rain). Several partnerships exist with IRSN, INERIS and CETE Nord-Picardie, as well as with the Research and Innovation Division of the Ministry of Ecology (MTES). New developments take place continuously to ensure that the models reflect the state of the art in atmospheric modeling. Current efforts focus on the improvements of atmospheric dispersion of the emissions from roadway traffic and tall stacks to provide better estimates of the potential impacts of those sources on air quality, and the comparison of various algorithms to simulate ozone formation, particulate matter formation and horizontal and vertical dispersion of atmospheric pollutants. A large program is also ongoing on the improvement of existing models for simulating atmospheric aerosols, including secondary organic aerosols and ultrafine particulate matter.
  
  
• Data Assimilation and Inverse Modeling
  Research activities include the development of data assimilation methods that combine numerical models and observations, inverse modeling, and the application of optimization methods to environmental problems. Typical applications are the improvement of air quality forecasts via satellite data assimilation, optimal combination of model ensembles, and inverse modeling of pollutant emissions (for example, to estimate an accidental release of radionuclides from a nuclear power plant). Other applications address, for example, the optimal design of monitoring networks for radionuclides and photochemical pollutants (for example, ozone).