Synoptic Climatology of Air Pollution in Moscow

Summary Seasonal synoptic indices are developed employing principal components analysis and cluster analysis for Moscow and using surface and upper air meteorological data. Synoptic types are analysed in terms of circulation patterns and air mass characteristics. The indices are used to examine weather-induced variability in CO and NO₂ concentrations for different land use types and in the context of multiple pollution sources. Anticyclonic conditions in spring, summer and autumn are identified as producing high pollution concentrations. Local depressions developing in the low pressure gradient fields in summer are another synoptic type resulting in high levels of air pollution. Extremely cold anticyclonic conditions in winter result in high CO but low NO₂ levels. Weather patterns characterised by strong winds associated either with an established zonal flow or the passage of a cold front caused high NO₂ concentrations in the areas affected by elevated sources. Received October 28, 1997 Revised January 26, 1998