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Publication Date
1 October 2021

The Influence of Atmosphere–Ocean Coupling on Simulated and Projected Tropical Cyclone Precipitation

Subtitle
Tropical cyclone precipitation is projected to increase with climate change independent of ocean coupling, however the magnitude of the increase can vary by a factor of three depending on ocean coupling.
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Science

Heavy tropical cyclone (TC) precipitation and associated floods can have substantial economic and human impacts.  Reliable future projections of TC precipitation are needed to prepare for coastal impacts. However, biases in global climate models (GCMs) associated with an inaccurate representation of atmosphere-ocean interactions can reduce confidence in projections of TC precipitation. This study aims to quantify the influence of atmosphere-ocean interactions on simulated and projected TC precipitation.

Impact

Characterizing the influence of atmosphere-ocean interactions on TC precipitation is crucial to improving simulated TC precipitation, as a more accurate simulation facilitates a more robust assessment of future climate change risk. This study shows that fully coupled atmosphere-ocean GCMs generally produce less TC precipitation than atmosphere-only GCMs. The reduction in simulated TC precipitation due to ocean coupling is associated with large-scale SST biases and local TC–ocean interactions. In addition, we found that although TC precipitation during 2015–2050 is predicted to increase in most TC basins, the magnitude can vary by a factor of three depending on ocean coupling.

Summary

To quantify the influence of atmosphere-ocean interactions on simulated TC precipitation, we used low- and high-resolution multi-model ensembles from the High-Resolution Model Intercomparison Project (HighResMIP). We compared simulations from the fully coupled atmosphere-ocean GCMs (AOGCMs) and atmosphere-only GCMs (AGCMs) over 1950–2050. We found that the fully coupled atmosphere-ocean GCM simulations generally produce lower TC precipitation than the atmosphere-only GCM simulations (i.e., SSTs prescribed from observations). The precipitation decrease is associated with large-scale SST biases and local TC–ocean feedbacks via SST cooling that is driven by TC wind-induced ocean mixing, common features in the GCM simulations with active atmosphere-ocean coupling. The two features influence TC precipitation by decreasing TC intensity and specific humidity. During the period 2015–2050, TC precipitation is predicted to increase in most TC basins by both the fully coupled and atmosphere-only GCM simulations. However, the magnitude can vary by a factor of 3 depending on ocean coupling.

Point of Contact
Huanping Huang
Institution(s)
Lawrence Berkeley National Laboratory
Funding Program Area(s)
Publication