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Model Spread in Tropical Low Cloud Feedback Tied to the Overturning Circulation Response to Warming

Presentation Date
Thursday, January 27, 2022 at 4:15pm
George R. Brown Convention Center - Remote



In the tropics, the intermodel spread in subsidence strength response to surface warming drives ~40% of the spread in low cloud fraction change among the climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). The intermodel spread in the ω500d change is linked to high cloud fraction and ascent area changes. A greater reduction in HCF corresponds to increased atmospheric longwave cooling, a smaller reduction in subsidence strength, a greater reduction in low cloud fraction and thus a stronger positive cloud feedback (Radiation-Subsidence Pathway). Additionally, predicted changes to subsidence are strongly controlled by a model’s climatological static stability, which is highly sensitive to the processes controlling deep convective initiation (Stability Pathway). In this presentation, I will discuss how these pathways contribute substantially to the inter-model spread of climate sensitivity in CMIP6 by linking deep convective processes to low cloud feedback through changes to the large-scale overturning circulation. Observational evidence for these pathways will also be presented and discussed.

Funding Program Area(s)