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 (BC) 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 is imposed at TOA, the net
shortwave radiation at the surface decreases by -5.87±0.67 W m−2 (W m−2)−1 (averaged over global land without Antarctica), which is
partially offset by increased downward longwave radiation (2.32±0.38 W m−2 (W m−2)−1 from the warmer atmosphere, causing a net
decrease in the incoming downward surface radiation of -3.56±0.60 W m−2 (W m−2)−1. Despite a reduction in the downward radiation
energy, the surface air temperature still increases by 0.25±0.08 K
because of less efficient energy dissipation, manifested by reduced surface
sensible (-2.88±0.43 W m−2 (W m−2)−1) and latent heat flux
(-1.54±0.27 W m−2 (W m−2)−1), as well as a decrease in
Bowen ratio (-0.20±0.07 (W m−2)−1). Such reductions of turbulent
fluxes can be largely explained by enhanced air stability (0.07±0.02 K (W m−2)−1), 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 (W m−2)−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
occur in the lower atmosphere and propagate downward to influence the
surface energy redistribution and thus surface temperature response, which
is not observed under greenhouse gases or scattering aerosols. Our study
provides new insights into the impact of absorbing aerosols on surface
energy balance and surface temperature response.