Urban aerosol, its radiative and temperature response in comparison with urban canopy effects in megacity based on COSMO-ART modeling

Abstract

The study of urban aerosol and its influence on radiation and meteorological regime is important due to the climate effect. Using COSMO-ART model with TERRA_URB parameterization, we estimated aerosols and their radiative and temperature response at different emission levels in Moscow. Mean urban aerosol optical depth (AOD) was about 0.029 comprising 20–30% of the total AOD. Urban black carbon mass concentration and urban PM10 accounted for 86% and 74% of their total amount, respectively. The urban AOD provided negative shortwave effective radiative forcing (ERF) of −0.9 W m−2 at the top of the atmosphere (TOA) for weakly absorbing aerosol and positive ERF for highly absorbing aerosol. Urban canopy effects decreased surface albedo from 19.1% to 16.9%, which resulted in positive shortwave ERF at TOA, while for longwave irradiance negative ERF was observed due to additional emitting of urban heat. Air temperature at 2 m decreased independently on the ERF sign, partially compensating (up to 0.5 °C) for urban heat island effect (1.5 °C) during daytime. Mean radiative atmospheric absorption over the Moscow center in clear sky conditions reaches 4 W m−2 due to urban AOD. The study highlights the role of urban aerosol and its radiative and temperature effects.