Dynamics of simulated Atlantic upwelling annual cycle in CMIP5 models

As one of the prominent climatic component of tropical climate system, the annual cycle of the equatorial Atlantic cold tongue region has been a subject of significant research. In this work, we examine the fidelity of the key part of the annual cycles, namely, the upwelling annual cycles, from the...

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Vydáno v:	Journal of geophysical research. Oceans Ročník 122; číslo 7; s. 5774 - 5785
Hlavní autoři:	Wang, Li‐Chiao, Jin, Fei‐Fei, Wu, Chau‐Ron
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	Washington Blackwell Publishing Ltd 01.07.2017 American Geophysical Union
Témata:	Amplification Annual Annual cycles Annual variations Atlantic Atmospheric circulation Bias Climate Climate models Climate system CMIP5 Cold regions Components Computer simulation Cycles Dynamics ENVIRONMENTAL SCIENCES Equatorial regions Equatorial upwelling Fields Frameworks Geophysics Intercomparison Local winds Meteorology Ocean circulation Ocean models Ocean-atmosphere interaction Oceans Simulation Tropical climate Tropical climates tropics Upwelling wind Wind fields
ISSN:	2169-9275, 2169-9291
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Popis
Shrnutí:	As one of the prominent climatic component of tropical climate system, the annual cycle of the equatorial Atlantic cold tongue region has been a subject of significant research. In this work, we examine the fidelity of the key part of the annual cycles, namely, the upwelling annual cycles, from the simulations of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Utilizing the simple framework we have recently developed based on the Zebiak‐Cane (ZC) ocean model, we first tested the validity of the simple framework of upwelling as a combination of the local wind‐driven Ekman upwelling and nonlocal wind‐driven wave upwelling. It is demonstrated that the theoretically reconstructed upwelling annual cycles to large extent are in good agreement with the simulations in these coupled climatic models. Comparing with observations, we show that the semiannual component of the upwelling is systematically too strong. This significant bias is attributable to the dynamic amplification to the wind‐driven wave upwelling originated from a less significant bias in the semiannual harmonic component in the central equatorial wind field. The latter is dynamically amplified in the wind‐driven wave upwelling owing to its relatively fast time scale. Thus, the realistic simulations of equatorial annual cycles may sensitively depend on good simulations of the semiannual harmonic components in equatorial wind fields. Key Points The simple theory based on the framework of Zebiak‐Cane ocean model for upwelling annual cycle also works well in CMIP5 simulations The semiannual component of the upwelling annual cycles in CMIP5 is systematically too strong owing to the dynamic amplification The realistic simulations of equatorial upwelling annual cycles may sensitively depend on good simulations of central equatorial wind fields
Bibliografie:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23 SC0005110; 105-2119-M-003-003; 104-2611-M-003-002-MY3 USDOE Office of Science (SC)
ISSN:	2169-9275 2169-9291
DOI:	10.1002/2017JC012781