The main purpose of this study was to estimate hourly meansurface photolysis rate coefficients of nitrogen dioxide for the atmospherein Buenos Aires city during cloud free conditions. A nine years periodof Aerosol Optical Depth (AOD) was used as input data to run theTUV (Tropospheric Ultraviolet Visible) model. Results showed thatmonthly maxima of surface photolysis rate doubles from winter tosummer. The study of a three month biomass burning period occurredat 70 km north from Buenos Aires City also showed an impact in thevariable studied.Photolysis rate coefficient in Buenos Aires city