Section: Software and Platforms


Participants : Sylvain Doré, Vivien Mallet, Florian Couvidat [CEREA] , Yiguo Wang [CEREA] , Nora Duhanyan [CEREA] , Yelva Roustan [CEREA] .

Polyphemus (see the web site http://cerea.enpc.fr/polyphemus/ ) is a modeling system for air quality. As such, it is designed to yield up-to-date simulations in a reliable framework: data assimilation, ensemble forecast and daily forecasts. Its completeness makes it suitable for use in many applications: photochemistry, aerosols, radionuclides, etc. It is able to handle simulations from local to continental scales, with several physical models. It is divided into three main parts:

  • libraries that gather data processing tools (SeldonData), physical parameterizations (AtmoData) and postprocessing abilities (AtmoPy);

  • programs for physical preprocessing and chemistry-transport models (Polair3D, Castor, two Gaussian models, a Lagrangian model);

  • model drivers and observation modules for model coupling, ensemble forecasting and data assimilation.

Figure 1 depicts a typical result produced by Polyphemus.

Figure 1. Map of the relative standard deviation (or spread, %) of an ensemble built with Polyphemus (ozone simulations, μgm-3). The standard deviations are averaged over the summer of 2001. They provide an estimation of the simulation uncertainties.

Clime is involved in the overall design of the system and in the development of advanced methods in model coupling, data assimilation and uncertainty quantification (through model drivers and post-processing).

In 2013, Polyphemus has received numerous improvements on aerosol modeling, including better dynamics for organic aerosol formation and interactions between organic and inorganic aerosols. The data assimilation part of Polyphemus can now perform 3D data assimilation, taking advantage of Lidar data. Further integration of the data assimilation library Verdandi was also carried out.