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Linkage between Tropical Deep Convection and Low Cloud Feedback in GFDL Perturbed Physics Experiments

Presentation Date
Thursday, January 27, 2022 at 2:15pm
George R. Brown Convention Center - Remote



The linkage between tropical deep convection and low cloud feedback is investigated using the perturbed physics experiments (PPEs) with the GFDL AM4 model. Five experiments are designed with prescribed observed sea surface temperature (SST) and approximately three-fold variation in the entrainment rates in the deep convective parameterization. Systematic changes in large-scale circulation, precipitation, clouds and radiation are found as a result of the modified convective entrainment rate. When the entrainment rate is lower, the ascent strengthens in most convective regions and the subsidence rates in the Eastern Pacific and Atlantic are enhanced. Precipitation and clouds change correspondingly. In particular, the low cloud amount in the Eastern Pacific increases with decreasing entrainment rate.

These GFDL PPEs exhibit different characteristics in terms of the sensitivity of convection to surface warming when compared to previous CESM1 PPE results. For instance, the ascent weakens in warmer years while the ascent area widens. In addition, we have diagnosed several pathways through which deep convection and large-scale circulation modulate the low cloud response to surface temperature change, including the temperature-stability pathway, moisture-mixing pathway and radiation-subsidence pathway.

Funding Program Area(s)