EGU2020-7024, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-7024
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Local and remote causes of the equatorial Pacific cold sea surface temperature bias in the Kiel Climate Model

Yuming Zhang1,2, Tobias Bayr2, Mojib Latif2,3, Zhaoyang Song2, Wonsun Park2, and Annika Reintges2
Yuming Zhang et al.
  • 1National Marine Environmental Monitoring Center, Ocean Dynamics, Kiel, Germany (ymzhang85@126.com)
  • 2GEOMAR Helmholtz Centre for Ocean Research Kiel, 24105 Kiel, Germany
  • 3Cluster of Excellence “The Future Ocean”, University of Kiel, 24105 Kiel, Germany

We investigate the origin of the equatorial Pacific cold sea surface temperature (SST) bias and its link to wind biases, local and remote, in the Kiel Climate Model (KCM) with dedicated coupled and stand-alone atmosphere model experiments. In the coupled experiments, the National Centers for Environmental Prediction Climate Forecast System Reanalysis (NCEP/CFSR) wind stress is prescribed over four different spatial domains: globally, over the equatorial Pacific (EP), the northern Pacific (NP) and southern Pacific (SP). The corresponding cold SST bias over the equatorial Pacific is reduced by 94%, 48%, 11% and 22%, respectively. Thus, the equatorial Pacific SST bias is mainly attributed to the wind bias over the EP region, with small but not negligible contributions from the SP and NP regions. Biases in the ocean dynamics cause the EP SST bias, while the atmospheric thermodynamics counteract it.

To examine the origin of wind biases, we force the atmospheric component of the KCM in stand-alone mode by observed SSTs and simulated SSTs from the coupled experiments with the KCM. The results show that wind biases over the EP, NP and SP regions are initially generated in the atmosphere model and further enhanced by the biased SST in the coupled model.

We conclude that the cold SST bias over the equatorial Pacific originates from biases in the ocean circulation that are forced by the biased surface winds over the EP, NP and SP regions. On the other hand, the cold equatorial Pacific SST bias amplifies the wind biases over the EP, NP and SP regions, which in turn enhances the cold SST bias by ocean-atmosphere coupling.

How to cite: Zhang, Y., Bayr, T., Latif, M., Song, Z., Park, W., and Reintges, A.: Local and remote causes of the equatorial Pacific cold sea surface temperature bias in the Kiel Climate Model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7024, https://doi.org/10.5194/egusphere-egu2020-7024, 2020