Meteorological Prerequisites of Formation of Severe Wintertime Air Pollution Episodes in Moscow

I. N. Kuznetsova, M. I. Nakhaev, I. Yu. Shalygina, and E. A. Lezina

Large-scale and local weather conditions during severe wintertime air pollution episodes in the Moscow megalopolis are analyzed. Concentrations of CO, NO, and NO2 obtained from the automated network of the atmosphere pollution control are used as tracers for atmospheric processes in the urban atmospheric boundary layer. It is shown that a high surface air pollution level in the city is formed at a weak wind in the lower atmosphere and only in the presence of a surface or low elevated temperature inversion. Temperature contrasts in the urban heat island generate the circulation that promotes air pollution in megapolis regions remote from large emission sources. It is supposed that in case of severe frosts the amount of anthropogenic heat in the megapolis sharply increases, promoting active turbulent mixing, thus preventing pollution accumulation in the surface air.