12 May 2021

12 May 2021

Review status: this preprint is currently under review for the journal ACP.

Distinct surface response to black carbon aerosols

Tao Tang1, Drew Shindell2, Yuqiang Zhang2, Apostolos Voulgarakis3,4, Jean-Francois Lamarque5, Gunnar Myhre6, Gregory Faluvegi7,8, Bjørn Samset6, Timothy Andrews9, Dirk Olivié10, Toshihiko Takemura11, and Xuhui Lee1 Tao Tang et al.
  • 1School of the Environment, Yale University, New Haven, CT, USA
  • 2Division of Earth and Climate Sciences, Duke University, Durham, NC, USA
  • 3Leverhulmn Centre for Wildfires, Environment and Society, Department of Physics, Imperial College London, London, UK
  • 4School of Environmental Engineering, Technical University of Crete, Chania, Greece
  • 5National Center for Atmospheric Research, Boulder, CO, USA
  • 6CICERO, Center for International Climate and Environment Research, Oslo, Norway
  • 7Center for Climate System Research, Columbia University, New York, NY, USA
  • 8NASA Goddard Institute for Space Studies, New York, NY, USA
  • 9Met Office Hadley Centre, Exeter, UK
  • 10Norwegian Meteorological Institute, Oslo, Norway
  • 11Kyushu University, Fukuoka, Japan

Abstract. For the radiative impact of individual climate forcings, most previous studies focused on the global mean values at the top of the atmosphere (TOA) and less attention has been paid to surface processes, especially for black carbon aerosols. In this study, the surface radiative responses to five different forcing agents were analyzed by using idealized model simulations. Our analyses reveal that for greenhouse gases, solar irradiance and scattering aerosols, the surface temperature changes are mainly dictated by the changes of surface radiative heating, but for BC, surface energy redistribution between different components plays a more crucial role. Globally, when a unit BC forcing was imposed at TOA, the net shortwave radiation at the surface decreased by 5.09 ± 1.80 W m−2 (averaged over global land), which is partially offset by increased downward longwave radiation (1.67 ± 0.24 W m−2) from the warmer atmosphere, causing a net decrease in the incoming downward surface radiation of 3.42 ± 0.51 W m−2. Despite a reduction in the downward radiation energy, the surface air temperature still increased by 0.14 ± 0.05 K because of less efficient energy dissipation, manifested by reduced surface sensible (2.53 ± 0.37 W m−2) and latent heat flux (1.30 ± 0.27 W m−2), as well as a decrease of Bowen ratio (0.18 ± 0.05). Such reductions of turbulent fluxes can be largely explained by enhanced air stability (0.06 ± 0.01 K), measured as the difference of the potential temperature between 925 hPa and surface, and reduced surface wind speed (0.05 ± 0.01 m s−1). The enhanced stability is due to the faster atmospheric warming relative to the surface whereas the reduced wind speed can be partially explained by enhanced stability and reduced equator-to-pole atmospheric temperature gradient. These rapid adjustments under BC forcing exerted a “top-down” impact on the surface energy redistribution and thus, surface temperature response, which is not observed under greenhouse gas or scattering aerosols. Our study provides new insights into the impact of absorbing aerosols on surface energy balance and surface temperature response.

Tao Tang et al.

Status: open (until 07 Jul 2021)

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  • RC1: 'Review of "Distinct surface response to black carbon aerosols"', Anonymous Referee #1, 07 Jun 2021 reply

Tao Tang et al.


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Short summary
Previous studies showed that black carbon (BC) could warm the surface with decreased incoming radiation. With climate models, we found that the surface energy redistribution plays a more crucial role on surface temperature compared with other forcing agents. Though BC could reduce the surface heating, the energy dissipates less efficiently, manifested by reduced convective and evaporative cooling, making temperature response positive.