Variations of the total content of carbon monoxide over Moscow megapolis

Abstract

The results of the carbon monoxide total content measurements over Moscow and Zvenigorod for 2005-2008 are compared with the same data sets for Moscow 1986-2005 and Beijing, 1992-2007. Two iden� tical medium resolution diffraction spectrometers (resolution 0.2 cm -1 ) with solar tracking system were used. The CO total content measured simultaneously over the city and over Zvenigorod Scientific Station (ZSS) of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (60 km west from Moscow). This method allows to isolate an urban part of CO content. The acoustic locator SODAR LATAN�3 mea� surements permitted us to study the influence of the carbon monoxide ventilation conditions upon level of pollution. Correlation coefficients between the urban part of CO content and average wind speed for cold and warm seasons were obtained. The data sets analysis showed a preeminent effect of the wind within boundary layer (up to 300 m) over the CO ventilation. The urban part of the CO content hasn't increased in spite of more than quintuple increase of the motorvehicles numb er in Moscow. An increase of the rural CO total col� umn for the 1970-1985 has transformed into its virtually stable amount in between of 1986 to 2000, changed then to a decrease for 2001-2008. We noted the 2008 as "the year of the CO total column minimum" over the past decade. The effect of urban CO sources influence on the CO total column in rural area is small, i.e. on a level of 3% of the total number of measurements. The number of extremal daily values for Moscow is estimated as 5%, and 20% for Beijing.