A hindcast approach to diagnosing the equatorial Pacific cold tongue SST bias in CESM1

An ensemble seasonal hindcast approach is used to investigate the development of the equatorial Pacific Ocean cold sea surface temperature (SST) bias and its characteristic annual cycle in the Community Earth System Model, version 1 (CESM1). In observations, eastern equatorial Pacific SSTs exhibit a warm phase during boreal spring and a cold phase during late boreal summer-autumn. The CESM1 climatology shows a cold bias during both warm and cold phases. In our hindcasts, the cold bias during the cold phase develops in less than 6 months, whereas the cold bias during the warm phase takes longer to emerge. The fast-developing cold-phase cold bias is associated with too-strong vertical advection and easterly wind stress over the eastern equatorial region. The antecedent boreal summer easterly wind anomalies also appear in atmosphere-only simulations, indicating that the errors are intrinsic to the atmosphere component. For the slower-developing warm-phase cold bias, we find that the too-cold SSTs over the equatorial region are associated with a slowly evolving upward displacement of subsurface ocean zonal currents and isotherms that can be traced to the ocean component.

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Author Siongco, Angela Cheska
Ma, Hsi-Yen
Klein, Stephen A.
Xie, Shaocheng
Karspeck, Alicia
Raeder, Kevin
Anderson, Jeffrey L.
Publisher UCAR/NCAR - Library
Publication Date 2020-02-01T00:00:00
Digital Object Identifier (DOI) Not Assigned
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Topic Category geoscientificInformation
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Metadata Date 2023-08-18T18:35:19.491615
Metadata Record Identifier edu.ucar.opensky::articles:23101
Metadata Language eng; USA
Suggested Citation Siongco, Angela Cheska, Ma, Hsi-Yen, Klein, Stephen A., Xie, Shaocheng, Karspeck, Alicia, Raeder, Kevin, Anderson, Jeffrey L.. (2020). A hindcast approach to diagnosing the equatorial Pacific cold tongue SST bias in CESM1. UCAR/NCAR - Library. http://n2t.net/ark:/85065/d7q81h8k. Accessed 15 July 2024.

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