The radiative and temperature effect of urban aerosol and its dependence on surface albedo according to experiments with the ICON-ART model and measurements at the MSU Meteorological Observatory in Moscow

Atmospheric aerosols partially absorb and scatter radiation in the atmosphere. Radiative effects of aerosols are negative on average, so aerosols slightly cool the atmosphere. However, recent studies indicate that in conditions with high surface albedo, the aerosol direct radiative effect (ADRE) can become positive, which leads to warming of the atmosphere (Chen et al., 2024).

To analyze the ADRE in Moscow and its dependence on surface albedo, a set of numerical experiments was carried out using the ICON-ART (Rieger et al., 2015) chemical transport model. ICON-ART currently does not include anthropogenic aerosols, so a dataset of aerosol optical properties was created with the MOPSMAP software package (Gasteiger, Wiegner, 2018). This dataset is based on AERONET Aerosol Inversion products (Dubovik, King, 2000) retrieved from measurements which were carried out at the MSU Meteorological Observatory in 2010 – 2021.

The numerical experiments cover the period between February 24^th and February 28^th, 2025. They were carried out with three different surface albedo values, 0.18, 0.4 and 0.65, which correspond to no snow, partial snow and snow conditions in Moscow. The results show that in high-surface-albedo conditions (A = 0.65), the ADRE becomes positive when solar height exceeds 18° and increases with aerosol load. When the surface albedo is equal to 0.4, the ADRE is about -1 W/m² and it does not depend on aerosol content. In conditions with no snow, the ADRE is negative and decreases with aerosol load. Thus, the ADRE strongly depends on surface albedo and during sunny weather, a strong positive ADRE occurs in polluted areas covered by snow.

The aerosol temperature effect was also studied. It is positive at the top of the boundary layer and negative at the surface level, which is in accordance with (Yang et al., 2021), although the values do not exceed ±0.1 °C.