Influence of meteorological conditions on variations and their long-term trends the carbon monoxide total content in the Moscow megacity.

This paper presents the results of comprehensive analysis of CO total content (CO TC) long-term spectroscopic measurements data at A.M. Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences (OIAP RAS) stations in Moscow and Moscow Region (Zvenigorod Scientific Station, ZSS). Meteorological parameters and CO long-term variations in atmospheric boundary layer (PBL) have been also studied. A decrease in average CO TC annual values in 2000-2023 was (-2.23±0.36%/year) for Moscow and (-1.12±0.33%/year) for ZSS. Additionally, CO TC trends characteristics was considered for both stations in different seasons and years.

After 2008, decline rate in CO emissions decreased at both stations. So, in 2000-2009 CO TC was decreasing at a rate -2.12%/year in Moscow and -1.59%/year in ZSS, and in 2009-2023 it was -1.78%/year for Moscow and -0.75%/year for Zvenigorod (estimates based on annual averages). During warm period of 2009-2023, no significant changes in CO TC were found for Moscow Region – the trend value is close to zero (0.04±0.92%/year).

According to aerological sounding data, an increase in wind speed in Moscow in 2003-2020 was detected by 0.88±0.39%/year (according to annual averages). At the same time, no statistically significant changes in wind speed were found in Kaluga Region (0.06±0.39%/year).

Episodes of CO accumulation in Moscow megacity atmosphere during calm days was investigated and analyzed. The average accumulation rate was 4.89 ± 0.32%/hour.

The obtained estimates of CO TC and wind speed trends indicate not only a reduction in anthropogenic emissions in Moscow, but also a influence of meteorological factor on air quality in Moscow.