Variability of trace gases in the atmospheric surface layer from observations in the city of Moscow

Abstract

The results of continuous minute measurements of the surface concentrations of ozone, nitric oxide, nitrogen dioxide, carbon monoxide, and sulfur dioxide during the 2002–2004 period at the environmental station of the Oboukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP), and the Faculty of Geography, Moscow State University (MSU), are discussed. It is shown that the conditions of Moscow’s southwestern region remote from large local pollution sources reflect the general regularities of the variability of trace gases in an urban atmosphere. This is manifested in the mean annual value of the ratio NO/NO2 (a little less than 1), decreased daylight values of O3, increased values of the rest of the trace gases as compared to the background region, and the presence of a secondary nocturnal maximum in the diurnal cycle of O3. The features of the annual and diurnal cycles of the concentrations of the substances under analysis are discussed. In the diurnal cycle of the primary products of combustion (NO and CO), an excess of the morning maximum (over the evening one) is observed during both warm and transition periods and higher values of the night maximum (as compared to the daylight one) are noted for summer. The temperature stratification properties determined from the MSU long-term acoustic sounding data serve as a possible cause for both of the effects revealed. The annual cycle of the concentration of surface ozone is characterized by the highest values for spring and summer. The annual cycles of NO, NO2, CO, and SO2 do not demonstrate any obvious seasonal regularities. A significant seasonal variation of the ratio NO/NO2, which is associated with the oxidizing properties of the urban atmosphere, is revealed. The record high concentrations of trace gases in the atmosphere over Moscow are given, and the meteorological conditions for their accumulation are discussed.