Decomposing Effective Radiative Forcing due to Aerosol Cloud
Interactions by Global Cloud Regimes
Quantifying Effective Radiative Forcing due to aerosol-cloud
interactions (ERFACI) remains a largely uncertain
process, and the magnitude remains unconstrained in general circulation
models. Previous studies focus on the magnitude of
ERFACI arising from all cloud types, or examine it in
the framework of dynamical regimes. Aerosol forcing due to aerosol-cloud
interactions in the HadGEM3-GA7.1 global climate model is decomposed
into several global observational cloud regimes. Regimes are allocated
to model gridboxes and forcing due to aerosol-cloud interactions is
calculated on a regime-by-regime basis with a 20-year meaning period.
Patterns of regime occurrence are in good agreement with satellite
observations. ERFACI is then further decomposed into
three terms, representing radiative changes within a given regime,
transitions between different cloud regimes, and nonlinear effects. The
total global mean ERFACI is -1.8 Wm-2.
When decomposed, simulated ERFACI is greatest in the
stratocumulus regime (-0.75 Wm-2).