Aerosol pollution in the Moscow megacity environment and its impact on radiative and meteorological properties of the atmosphere

Urban aerosol pollution has a significant effect on solar irradiance and meteorological characteristics. Using the two online integrated meteorology – atmospheric composition modelling systems  -  COSMO-Ru2-ART (Consortium for Small-scale Modeling – Aerosols and Reactive Trace gases) and Enviro-HIRLAM (Environment – High Resolution Limited Area Model) ) taking into account urbanization effects, we studied the effects of aerosol pollution and its impact on radiative and meteorological characteristics of the atmosphere with focus on the Moscow megacity region (Russia). For the models’ runs, the initial and boundary conditions from the ICON-COSMO-Ru7 and ERA-5  as well as the CAMS redistributed inventory emissions were utilized.

In order to account for the absorbing aerosol properties of the Moscow urban atmosphere black carbon (BC) emissions were applied according to the ECLIPSE emission inventory, which demonstrated a satisfactory agreement in BC/PM10 ratio with experimental data in Moscow.  A series of models’ simulations over an area of 300x300 km  was performed with a 2 km horizontal grid step with the effects of urban areas (building effects/ BEP, anthropogenic heat fluxes/ AHF in Enviro-HIRLAM and TERRA_URB scheme in COSMO-Ru2-ART), and without their consideration. The estimates of urban aerosol content were made for typical conditions in April-May 2019 and during spring of 2020, when lowered anthropogenic emissions were observed in the Moscow region due to strict lockdown conditions of COVID-19 pandemic.

In this study, we accounted for the changes in emissions for the lockdown situation according to the recommendations (Le Quéré et al., 2020), which were mainly in agreement with the official statements.  The estimates of aerosol urban properties were tested against the difference between the AERONET measurements obtained in the Moscow megacity and in a relatively clean region at Zvenigorod Scientific Station of the Institute of Atmospheric Physics, Russian Academy of Sciences.  The quality of surface aerosol estimation was verified using the MosEcoMonitoring Agency dataset. The variability of concentration of different aerosol species at ground level and changes in aerosol optical depth and its absorbing properties in the total atmospheric column are discussed.  The various aerosol radiative effects - direct, semidirect and indirect - and the influence of aerosol on selected meteorological characteristics (such as temperature, humidity, cloud cover, etc.) are analyzed. The features of spatio-temporal changes in urban aerosol fields and their effects on meteorology in conditions of elevated and lower emissions of pollutants in typical and lockdown conditions are investigated. 

This study is partially supported by the Ministry of Education and Science of the Russian Federation (grant number 075-15-2021-574) and the Finnish Flagship “Atmosphere and Climate Competence Center” (Academy of Finland grant 337549).  This research was performed according to the Development Programme of the Interdisciplinary Scientific and Educational School of MSU “Future Planet and Global Environmental Change”. The CSC - IT Center for Science Computing (Finland), is acknowledged for computational resources.

References:

Le Quéré C. et all (2020): Temporary reduction in daily global CO₂ emissions during the COVID-19 forced confinement, Nat. Clim. Change, 10, 647–653.