Séminaire le jeudi 18 novembre (amphitéâtre à Guyancourt, 11h): Dmitry Ionov (St.Petersburg State University, Physics of Atmosphere, Research Institute of Physics, St. Petersburg, Russie): "NO2 pollution monitoring above the city of St.Petersburg using ground-based spectroscopic measurements". Measurements of NO2 vertical columns are carried out at St.Petersburg State University by means of zenith-sky spectroscopy in the visible range of spectra (DOAS). The measurements are fully automated and run continuously since 2004. Although our instrument is installed in the suburb area, it is exposed to intense pollution from the city of St.Petersburg. The talk will present the estimates of tropospheric NO2 column over St.Petersburg, in comparison with nadir satellite (OMI) and local ground-based (in situ) measurements, and regional dispersion modeling (HYSPLIT). Also, some preliminary results of mobile DOAS measurements of tropospheric NO2 around St.Petersburg will be given.