PHOTONS/AERONET sunphotometer network overview. Description - Activities - Results

PHOTONS is the french component of the AERONET sun-photometer network which provides globally distributed near-real-time observations of aerosol spectral optical depth and sky radiance as well as derived parameters such as particle size distributions, single-scattering albedo and complex refractive index. Now more than 12 years of worldwide distributed data from the network of ground-based radiometers are available. These data are best suited to reliably and continuously derive the detailed aerosol optical properties in key locations. Mid 2007, about 40 sites mainly located in France, Europe, Africa as well as in Asia are managed by PHOTONS. Since 2001, the network also contributes to passive/active sensors synergies. Several sites in France, western as well as eastern Europe, sometimes in connection with EARLINET, are equipped with both lidar system and sun-photometer dedicated to aerosol and cloud observations. These synergies will be enhanced in the future mainly within the context of A-Train experience. In this paper, we provide a general description of PHOTONS network activities and facilities, and present recent results both on instrumental side (development on new sun-photometer, vicarious calibration methods), on scientific side (A-Train mission validation like aerosol retrieval algorithms of PARASOL) and aerosols retrieval from ground-based measurements method.