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Cloud Responses to Abrupt Solar and CO2 Forcing Part II: Adjustment to Forcing in Coupled Models
  • Travis Aerenson,
  • Roger Marchand,
  • Chen Zhou
Travis Aerenson
University of Washington

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Roger Marchand
University of Washington, Seattle, USA
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Chen Zhou
Nanjing University
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In this paper we examine differences in cloud adjustments (often called rapid adjustments) that occur as a direct result of abruptly increasing the solar constant by 4% or abruptly quadrupling of atmospheric CO2. In doing so, we devised a novel method for calculating the cloud adjustments for the abrupt solar forcing experiment that uses differences between coupled model simulations with abrupt solar and CO2 forcing, in combination with uncoupled, atmosphere-only, abrupt CO2 forced experiments that have prescribed sea-surface temperature. Our main findings are that 1) there are substantial differences in the response of stratocumulus and cumulus clouds to solar and CO2 forcing, which follow the differences in the direct radiative effect that solar and CO2 forcing have at cloud top, and 2) there are differences in the adjustment of the average optical depth of high clouds to solar and CO2 forcing that we speculate are driven by the differences in the vertical profile of radiative heating, and differences in the pattern of sea-surface temperature change (for a fixed global mean temperature). Such adjustments do contribute significantly to the total net cloud radiative effect, even after 150 years of simulation.
30 Oct 2023Submitted to ESS Open Archive
08 Nov 2023Published in ESS Open Archive