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An evaluation of the subtropical eastern North Pacific SST bias in the E3SM v1

Presentation Date
Thursday, December 10, 2020 at 4:00am



Warm SST biases in the subtropical Eastern Boundary Current (EBC) regions constitute a systematic and persistent problem affecting most coupled climate models. These regions are characterized by a strong coupling between cool SSTs, maintained in place by cold currents and coastal upwelling, and the marine stratocumulus cloud deck over them in the lower troposphere. This bias is complex as error in either the ocean or atmosphere could trigger an error in the other, and initial errors tend to get amplified by the positive feedback mechanisms operating between them. Besides these physical processes, the EBC regions also tend to be very productive biologically. Thus it is very important to evaluate the progress made by climate models in their simulation of SSTs in the subtropical EBC regions. In this study, we will perform a detailed examination of the warm SST bias in the subtropical eastern North Pacific using the fully-coupled Energy Exascale Earth System Model (E3SM) v1, a contributor to CMIP6. The model simulations at both the standard (110 km atm, 30-60 km ocn) and high-resolution (25 km atm, 6-18 km ocn) are being analyzed to provide hints on resolution impacts. We also compare E3SMv1 SST biases in the EBC regions from the full suite of CMIP5 and CMIP6 suite of models. Finally, besides the fully-coupled simulations, we will also analyze simulations in which the ocean model is forced with a data atmosphere to isolate the role of coupling.

Funding Program Area(s)