Present parameterizations of the UV surface albedo in global chemistry transport models are generally based on a crude land cover classification and do not account for interannual variations of the snow-covered surface or the large variability in the albedo of snow-covered surfaces. We developed an improved scheme based on 2 years of Moderate-Resolution Imaging Spectroradiometer (MODIS) albedo data, a fine-resolution MODIS land cover map, Global Ozone Monitoring Experiment (GOME) albedo data, and daily assimilated snow cover maps from the European Centre for Medium-Range Weather Forecasts or the National Centers for Environmental Prediction. The new parameterization improves the calculation of photolysis frequencies in particular in the subarctic region as shown by a comparison of the calculated ratio of upwelling and downwelling actinic fluxes with spectral measurements from the Tropospheric Ozone Production About Spring Equinox (TOPSE) campaign (January-May 2000). The impact of surface albedo changes on tropospheric photochemistry has been investigated using the global MOZART-2 chemistry transport model. Compared with the original model version, the surface albedo changes alter the tropospheric oxidizing capacity (OH concentrations) between -20 and +200% locally and +5% in the global annual mean. About half of this change results from a new value adapted for the ocean UV albedo. Locally, NOx concentrations were found to decrease by up to 40% and were most pronounced where the snow boundary crosses the high-emission regions in Europe, North America, and Asia. The interannual variability of snow and sea ice cover can lead to changes in the global tropospheric OH-concentration of 0.5%, which is of similar magnitude compared with the impacts of varying water vapor, transport, ozone column, and emissions as discussed in previous studies. Copyright 2005 by the American Geophysical Union.