Improved Simulations of Tropical Pacific Annual-Mean Climate in the GFDL FLOR and HiFLOR Coupled GCMs

Andrew T. Wittenberg; Gabriel Andres Vecchi; Thomas L. Delworth; Anthony Rosati; Whit G. Anderson; William F. Cooke; Seth Underwood; Fanrong Zeng; Stephen M. Griffies; Sulagna Ray

doi:10.1029/2018MS001372

Improved Simulations of Tropical Pacific Annual-Mean Climate in the GFDL FLOR and HiFLOR Coupled GCMs

Andrew T. Wittenberg, Gabriel Andres Vecchi, Thomas L. Delworth, Anthony Rosati, Whit G. Anderson, William F. Cooke, Seth Underwood, Fanrong Zeng, Stephen M. Griffies, Sulagna Ray

Research output: Contribution to journal › Article › peer-review

20 Scopus citations

Abstract

The National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory has recently developed two global coupled general circulation models, the Forecast-oriented Low Ocean Resolution (FLOR) model and the High atmospheric resolution Forecast-oriented Low Ocean Resolution (HiFLOR) model, which are now being utilized for climate research and seasonal predictions. Compared to their predecessor Coupled Model version 2.1 (CM2.1), the new versions have improved ocean/atmosphere physics and numerics and refinement of the atmospheric horizontal grid from 220 km (CM2.1) to 55 km (FLOR) and 26 km (HiFLOR). Both FLOR and HiFLOR demonstrate greatly improved simulations of the tropical Pacific annual-mean climatology, with FLOR practically eliminating any equatorial cold bias in sea surface temperature. An additional model experiment (Low Ocean Atmosphere Resolution version 1) using FLOR's ocean/atmosphere physics, but with the atmospheric grid coarsened toward that of CM2.1, is used to further isolate the impacts of the refined atmospheric grid versus the improved physics and numerics. The improved ocean/atmosphere formulations are found to produce more realistic tropical Pacific patterns of sea surface temperature and rainfall, surface heat fluxes, ocean mixed layer depths, surface currents, and tropical instability wave activity; enhance the near-surface equatorial upwelling; and reduce the intercentennial warm drift of the tropical Pacific upper ocean. The atmospheric grid refinement further improves these features and also improves the tropical Pacific surface wind stress, implied Ekman and Sverdrup transports, subsurface temperature and salinity structure, and heat advection in the equatorial upper ocean. The results highlight the importance of nonlocal air-sea interactions in the tropical Pacific climate system, including the influence of off-equatorial surface fluxes on the equatorial annual-mean state. Implications are discussed for improving future simulations, observations, and predictions of tropical Pacific climate.

Original language	English (US)
Pages (from-to)	3176-3220
Number of pages	45
Journal	Journal of Advances in Modeling Earth Systems
Volume	10
Issue number	12
DOIs	https://doi.org/10.1029/2018MS001372
State	Published - Dec 2018

All Science Journal Classification (ASJC) codes

Global and Planetary Change
Environmental Chemistry
General Earth and Planetary Sciences

Keywords

El Niño Southern Oscillation (ENSO)
air-sea interactions
coupled models of the climate system
tropical Pacific climate
upper ocean and mixed layer processes

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10.1029/2018MS001372

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title = "Improved Simulations of Tropical Pacific Annual-Mean Climate in the GFDL FLOR and HiFLOR Coupled GCMs",

abstract = "The National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory has recently developed two global coupled general circulation models, the Forecast-oriented Low Ocean Resolution (FLOR) model and the High atmospheric resolution Forecast-oriented Low Ocean Resolution (HiFLOR) model, which are now being utilized for climate research and seasonal predictions. Compared to their predecessor Coupled Model version 2.1 (CM2.1), the new versions have improved ocean/atmosphere physics and numerics and refinement of the atmospheric horizontal grid from 220 km (CM2.1) to 55 km (FLOR) and 26 km (HiFLOR). Both FLOR and HiFLOR demonstrate greatly improved simulations of the tropical Pacific annual-mean climatology, with FLOR practically eliminating any equatorial cold bias in sea surface temperature. An additional model experiment (Low Ocean Atmosphere Resolution version 1) using FLOR's ocean/atmosphere physics, but with the atmospheric grid coarsened toward that of CM2.1, is used to further isolate the impacts of the refined atmospheric grid versus the improved physics and numerics. The improved ocean/atmosphere formulations are found to produce more realistic tropical Pacific patterns of sea surface temperature and rainfall, surface heat fluxes, ocean mixed layer depths, surface currents, and tropical instability wave activity; enhance the near-surface equatorial upwelling; and reduce the intercentennial warm drift of the tropical Pacific upper ocean. The atmospheric grid refinement further improves these features and also improves the tropical Pacific surface wind stress, implied Ekman and Sverdrup transports, subsurface temperature and salinity structure, and heat advection in the equatorial upper ocean. The results highlight the importance of nonlocal air-sea interactions in the tropical Pacific climate system, including the influence of off-equatorial surface fluxes on the equatorial annual-mean state. Implications are discussed for improving future simulations, observations, and predictions of tropical Pacific climate.",

keywords = "El Ni{\~n}o Southern Oscillation (ENSO), air-sea interactions, coupled models of the climate system, tropical Pacific climate, upper ocean and mixed layer processes",

author = "Wittenberg, {Andrew T.} and Vecchi, {Gabriel Andres} and Delworth, {Thomas L.} and Anthony Rosati and Anderson, {Whit G.} and Cooke, {William F.} and Seth Underwood and Fanrong Zeng and Griffies, {Stephen M.} and Sulagna Ray",

note = "Publisher Copyright: {\textcopyright}2018. The Authors.",

year = "2018",

month = dec,

doi = "10.1029/2018MS001372",

language = "English (US)",

volume = "10",

pages = "3176--3220",

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T1 - Improved Simulations of Tropical Pacific Annual-Mean Climate in the GFDL FLOR and HiFLOR Coupled GCMs

AU - Wittenberg, Andrew T.

AU - Vecchi, Gabriel Andres

AU - Delworth, Thomas L.

AU - Rosati, Anthony

AU - Anderson, Whit G.

AU - Cooke, William F.

AU - Underwood, Seth

AU - Zeng, Fanrong

AU - Griffies, Stephen M.

AU - Ray, Sulagna

PY - 2018/12

Y1 - 2018/12

N2 - The National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory has recently developed two global coupled general circulation models, the Forecast-oriented Low Ocean Resolution (FLOR) model and the High atmospheric resolution Forecast-oriented Low Ocean Resolution (HiFLOR) model, which are now being utilized for climate research and seasonal predictions. Compared to their predecessor Coupled Model version 2.1 (CM2.1), the new versions have improved ocean/atmosphere physics and numerics and refinement of the atmospheric horizontal grid from 220 km (CM2.1) to 55 km (FLOR) and 26 km (HiFLOR). Both FLOR and HiFLOR demonstrate greatly improved simulations of the tropical Pacific annual-mean climatology, with FLOR practically eliminating any equatorial cold bias in sea surface temperature. An additional model experiment (Low Ocean Atmosphere Resolution version 1) using FLOR's ocean/atmosphere physics, but with the atmospheric grid coarsened toward that of CM2.1, is used to further isolate the impacts of the refined atmospheric grid versus the improved physics and numerics. The improved ocean/atmosphere formulations are found to produce more realistic tropical Pacific patterns of sea surface temperature and rainfall, surface heat fluxes, ocean mixed layer depths, surface currents, and tropical instability wave activity; enhance the near-surface equatorial upwelling; and reduce the intercentennial warm drift of the tropical Pacific upper ocean. The atmospheric grid refinement further improves these features and also improves the tropical Pacific surface wind stress, implied Ekman and Sverdrup transports, subsurface temperature and salinity structure, and heat advection in the equatorial upper ocean. The results highlight the importance of nonlocal air-sea interactions in the tropical Pacific climate system, including the influence of off-equatorial surface fluxes on the equatorial annual-mean state. Implications are discussed for improving future simulations, observations, and predictions of tropical Pacific climate.

AB - The National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory has recently developed two global coupled general circulation models, the Forecast-oriented Low Ocean Resolution (FLOR) model and the High atmospheric resolution Forecast-oriented Low Ocean Resolution (HiFLOR) model, which are now being utilized for climate research and seasonal predictions. Compared to their predecessor Coupled Model version 2.1 (CM2.1), the new versions have improved ocean/atmosphere physics and numerics and refinement of the atmospheric horizontal grid from 220 km (CM2.1) to 55 km (FLOR) and 26 km (HiFLOR). Both FLOR and HiFLOR demonstrate greatly improved simulations of the tropical Pacific annual-mean climatology, with FLOR practically eliminating any equatorial cold bias in sea surface temperature. An additional model experiment (Low Ocean Atmosphere Resolution version 1) using FLOR's ocean/atmosphere physics, but with the atmospheric grid coarsened toward that of CM2.1, is used to further isolate the impacts of the refined atmospheric grid versus the improved physics and numerics. The improved ocean/atmosphere formulations are found to produce more realistic tropical Pacific patterns of sea surface temperature and rainfall, surface heat fluxes, ocean mixed layer depths, surface currents, and tropical instability wave activity; enhance the near-surface equatorial upwelling; and reduce the intercentennial warm drift of the tropical Pacific upper ocean. The atmospheric grid refinement further improves these features and also improves the tropical Pacific surface wind stress, implied Ekman and Sverdrup transports, subsurface temperature and salinity structure, and heat advection in the equatorial upper ocean. The results highlight the importance of nonlocal air-sea interactions in the tropical Pacific climate system, including the influence of off-equatorial surface fluxes on the equatorial annual-mean state. Implications are discussed for improving future simulations, observations, and predictions of tropical Pacific climate.

KW - El Niño Southern Oscillation (ENSO)

KW - air-sea interactions

KW - coupled models of the climate system

KW - tropical Pacific climate

KW - upper ocean and mixed layer processes

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SN - 1942-2466

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JO - Journal of Advances in Modeling Earth Systems

JF - Journal of Advances in Modeling Earth Systems

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ER -

Improved Simulations of Tropical Pacific Annual-Mean Climate in the GFDL FLOR and HiFLOR Coupled GCMs

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