Abstract
AbstractBlack carbon (BC) aerosols influence precipitation through a range of processes. The climate response to the presence of BC is however highly dependent on its vertical distribution. Here, we analyze the changes in the energy budget and precipitation impacts of adding a layer of BC at a range of altitudes in two independent global climate models. The models are run with atmosphere‐only and slab ocean model setup to analyze both fast and slow responses, respectively. Globally, precipitation changes are tightly coupled to the energy budget. We decompose the precipitation change into contributions from absorption of solar radiation, atmospheric longwave radiative cooling, and sensible heat flux at the surface. We find that for atmosphere‐only simulations, BC rapidly suppresses precipitation, independent of altitude, mainly because of strong atmospheric absorption. This reduction is offset by increased atmospheric radiative longwave cooling and reduced sensible heat flux at the surface, but not of sufficient magnitude to prevent reduced precipitation. On longer timescales, when the surface temperature is allowed to respond, we find that the precipitation increase associated with surface warming can compensate for the initial reduction, particularly for BC in the lower atmosphere. Even though the underlying processes are strikingly similar in the two models, the resulting change in precipitation and temperature by BC differ quite substantially.
Highlights
Black carbon (BC) aerosols can influence precipitation by absorbing solar radiation and changing the atmospheric heating rates (Ming et al, 2010; Ramanathan et al, 2001)
instantaneous radiative forcing (IRF) increases with height because (i) the underlying albedo is higher for BC located above clouds, (ii) more Rayleigh scattering, and (iii) less competition from other absorbing components like water vapor and ozone higher up in the atmosphere (Samset & Myhre, 2011; Zarzycki & Bond, 2010)
The IRF is larger than effective radiative forcing (ERF) at TOA for all BC heights except for BC added close to the surface in Community Atmosphere Model version 4 (CAM4)
Summary
Black carbon (BC) aerosols can influence precipitation by absorbing solar radiation and changing the atmospheric heating rates (Ming et al, 2010; Ramanathan et al, 2001). The atmosphere rapidly adjusts to this added heat by changing the clouds, relative humidity, and precipitation These effects, which occur independently of any subsequent change in surface temperature, are commonly termed rapid adjustments to the instantaneous (direct) radiative forcing of BC (Boucher et al, 2013). Different climate forcers, such as BC, scattering aerosols or CO2, can induce very different rapid adjustments (on short timescale typically days) (Smith et al, 2018; Stjern et al, 2017). This is partly because of the complexity of BC RF on the climate, the vertical dependence on the climate response of BC, and the large negative fast precipitation changes due to strong absorption of solar radiation, all of which may be treated differently between current climate models
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
