Improved air-mass factors for ground-based total NO2 measurements: a sensitivity study

We present an overview of exisiting problems in air-mass factor calculations for NO2 vertical column measurements by UV-visible ground-based spectrometry, Sensitivity studies made using different radiative transfer models allow us to identify and to quantify sources of uncertainties in clculations, and domiment effects are multiple scattering (4%) and profile variations due to diurnal (10%) and seasonal changes (16%