Abstract
AbstractAbsorbing aerosol from biomass burning impacts the hydrological cycle and radiation fluxes both directly and indirectly via modifications to convective processes and cloud development. Using the ICOsahedral Non‐hydrostatic modelling framework in a regional configuration with 1,500 m convection‐permitting resolution, we isolate the response of the Amazonian atmosphere to biomass burning smoke via enhanced cloud droplet number concentrations Nd (aerosol‐cloud interactions; ACI) and changes to radiative fluxes (aerosol‐radiation interactions; ARI) over a period of 8 days. We decompose ARI into contributions from reduced shortwave radiation and localized heating of the smoke. We show ARI influences the formation and development of convective cells: surface cooling below the smoke drives suppression of convection that increases with smoke optical depth, while the elevated heating promotes initial suppression and subsequent intensification of convection overnight; a corresponding diurnal response (repeating temporal response day‐after‐day) from high precipitation rates is shown. Enhanced Nd (ACI) perturbs the bulk cloud properties and suppresses low‐to‐moderate precipitation rates. Both ACI and ARI result in enhanced high‐altitude ice clouds that have a strong positive longwave radiative effect. Changes to low‐cloud coverage (ARI) and albedo (ACI) drive an overall negative shortwave radiative effect, that slowly increases in magnitude due to a moistening of the boundary layer. The overall net radiative effect is dominated by the enhanced high‐altitude clouds, and is sensitive to the plume longevity. The considerable diurnal responses that we simulate cannot be observed by polar orbiting satellites widely used in previous work, highlighting the potential of geostationary satellites to observe large‐scale impacts of aerosols on clouds.
Highlights
Airborne aerosol particles, such as sea salt, mineral dust, or carbonaceous material, impact our climate via interactions with solar and terrestrial radiation known as aerosol-radiation interactions (ARI) and via their ability to act as cloud condensation nuclei (CCN) and subsequent follow-up effects
We show ARI influences the formation and development of convective cells: surface cooling below the smoke drives suppression of convection that increases with smoke optical depth, while the elevated heating promotes initial suppression and subsequent intensification of convection overnight; a corresponding diurnal response from high precipitation rates is shown
Our findings highlight important processes that are not sufficiently represented in global climate models, and highlight a need to use time-resolved geostationary satellite observations of the region to capture more of the diurnal cycle
Summary
Airborne aerosol particles, such as sea salt, mineral dust, or carbonaceous material, impact our climate via interactions with solar and terrestrial radiation known as aerosol-radiation interactions (ARI) and via their ability to act as cloud condensation nuclei (CCN) and subsequent follow-up effects (known as aerosol-cloud interactions; ACI). The first is the standard representation of BBA, with a maximum AOD of 1.5 and an SSA of 0.87, which results in localized heating of the aerosol layer and a reduced surface flux of shortwave (SW) radiation This peak AOD is within sustained magnitudes observed during this period (Figure 2a; see Schafer et al, 2008) and only represents a small region of the domain (Figure 3b). In order to achieve a consistent SW reduction at the surface, the AOD was increased by a factor of 2.55 (determined using SOCRATES: Suite of Community Radiation Codes based on Edwards & Slingo, 1996) This results in an unrealistically high AOD but for this experiment, we are only concerned with the effect that the changes to the surface fluxes have on the evolution of the domain
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.
