Assessing feedback of tropical instability wave‐induced wind stress perturbations in the equatorial Pacific

Wei, Yanzhou; Pei, Yuhua; Kang, Xiaojiao

doi:10.1002/joc.5906

Cited by 6 publications

(3 citation statements)

References 28 publications

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“…Wind stress corresponds to the force (per unit area) that the airflow exerts over a surface and is a measure of the transfer of momentum between the atmosphere and the ocean, and therefore provides a quantitative estimate of the air-sea coupling [68]. Wind stress plays a major role as a key mechanism to trigger instabilities [69] as well as influence rainfall [70]. The different mechanisms and interactions acting in the region are fundamental to determine the characteristics of rainfall.…”

Section: Large-scale Circulationmentioning

confidence: 99%

Climate Perspectives in the Intra–Americas Seas

et al. 2020

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The Intra–Americas Seas region is known for its relevance to air–sea interaction processes, the contrast between large water masses and a relatively small continental area, and the occurrence of extreme events. The differing weather systems and the influence of variability at different spatio–temporal scales is a characteristic feature of the region. The impact of hydro–meteorological extreme events has played a huge importance for regional livelihood, having a mostly negative impact on socioeconomics. The frequency and intensity of heavy rainfall events and droughts are often discussed in terms of their impact on economic activities and access to water. Furthermore, future climate projections suggest that warming scenarios are likely to increase the frequency and intensity of extreme events, which poses a major threat to vulnerable communities. In a region where the economy is largely dependent on agriculture and the population is exposed to the impact of extremes, understanding the climate system is key to informed policymaking and management plans. A wealth of knowledge has been published on regional weather and climate, with a majority of studies focusing on specific components of the system. This study aims to provide an integral overview of regional weather and climate suitable for a wider community. Following the presentation of the general features of the region, a large scale is introduced outlining the main structures that affect regional climate. The most relevant climate features are briefly described, focusing on sea surface temperature, low–level circulation, and rainfall patterns. The impact of climate variability at the intra–seasonal, inter–annual, decadal, and multi–decadal scales is discussed. Climate change is considered in the regional context, based on current knowledge for natural and anthropogenic climate change. The present challenges in regional weather and climate studies have also been included in the concluding sections of this review. The overarching aim of this work is to leverage information that may be transferred efficiently to support decision–making processes and provide a solid foundation on regional weather and climate for professionals from different backgrounds.

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Section: Large-scale Circulationmentioning

confidence: 99%

Climate Perspectives in the Intra–Americas Seas

et al. 2020

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“…Therefore, the τ TIW derived in this study are weaker than observed, and their effect on the ocean may be underestimated. However, the empirical τ TIW = F(SST) model established in this study is helpful in rectifying the misrepresented wind stress-SST coupling relationship at TIW scales in the ocean models (Chelton, 2005) and in assessing its feedback on the ocean (Wei, Pei, & Kang, 2019).…”

Section: Discussionmentioning

confidence: 97%

An Empirical Tropical Instability Wave-induced Wind Stress Model in the Equatorial Pacific and its Incorporation into the Ocean Model

2018

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Satellite observations revealed that there is a close relationship between perturbations of sea surface temperature (SST) and wind stress (τ) induced by tropical instability waves (TIWs; SST TIW and τ TIW ). Using the empirical relationship observed between TIW-induced wind stress divergence (curl) and downwind (crosswind) SST gradients, this study establishes a TIW-induced wind stress field perturbation model τ TIW = F(SST). This empirical model solves τ TIW from the TIW-induced wind stress divergence and curl, which are estimated from the downwind and crosswind SST gradients. This empirical τ TIW = F(SST) model can be incorporated into the ocean model to take into account the effect of τ TIW . By comparing two experiments with and without the τ TIW effect, this study demonstrates that τ TIW has a substantial effect on the equatorial Pacific heat budget and induces the long-term mean SST to exhibit a 0.2°C difference, which is consistent with previous studies. RÉSUMÉ [Traduit par la rédaction] Les observations émanant de satellites révèlent qu'il existe une relation étroite entre les ondes d'instabilité tropicales (TIW), et les perturbations de la température de surface de la mer (SST) et de la tension du vent (τ) que ces ondes induisent, soit SST TIW et τ TIW . Nous élaborons ici un modèle, τ TIW = F(SST), de perturbation du champ de la tension du vent que génèrent les TIW, et ce, en appliquant la relation empirique observée entre la divergence (le rotationnel) de la tension du vent et le gradient des SST en aval (perpendiculaire au vent), que produisent les TIW. Ce modèle empirique résout τ TIW à partir de la divergence et du rotationnel de la tension du vent qu'induisent les TIW, et ceux-ci sont estimés à partir des gradients de SST perpendiculaire au vent et en aval. Ce modèle empirique, τ TIW = F(SST), peut s'insérer dans le modèle océanique pour prendre en compte l'effet de τ TIW . En comparant des simulations avec et sans l'effet τ TIW , nous démontrons que τ TIW influe considérablement sur le bilan thermique du Pacifique équatorial et génère à long terme une différence de 0,2°C de la moyenne de la SST, ce qui concorde avec des études antérieures.

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“…From an oceanic model, Menkes et al (2006) also found an enhanced diffusivity in the cold cusps, and a reduced one in warm TIW areas, and their climatological heat budget of the cold tongue reveals a positive eddy mixing flux of 0.378C month 21 . However, it should be stressed that in some studies such as Moum et al (2009) and Wei et al (2019), the atmospheric forcing is included in the vertical mixing term as its boundary condition in surface. In our study and others (e.g., Menkes et al 2006;Graham 2014), the atmospheric forcing is an independent term, and the boundary condition of the vertical mixing rather depends on the wind stress.…”

Section: Summary and Discussionmentioning

confidence: 99%

Direct and Rectified Effects of Tropical Instability Waves on the Eastern Tropical Pacific Mean State in a Regional Ocean Model

Maillard

Boucharel

Renault

2022

Journal of Physical Oceanography

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Tropical instability waves (TIWs) are oceanic features propagating westward along the northern front of the pacific cold tongue. Observational and modeling studies suggest that TIWs may have a large impact on the eastern tropical Pacific background state from seasonal to interannual time-scales, through heat advection and mixing. However, observations are coarse or limited to surface data, and modeling studies are often based on the comparison of low- vs. high-resolution simulations. In this study, we perform a set of regional high-resolution ocean simulations (CROCO 1/12°) in which we strongly damp (NOTIWs-RUN) or not (TIWs-RUN) TIW propagation, by nudging meridional current velocities in the TIW region toward their monthly climatological values. This approach, while effectively removing TIW mesoscale activity, does not alter the model internal physics in particular related to the equatorial Kelvin wave dynamics. The impact of TIWs on the oceanic mean state is then assessed by comparing the two simulations. While the well-known direct effect of TIW heat advection is to weaken the meridional temperature gradient by warming up the cold tongue (0.34°C/month), the rectified effect of TIWs onto the mean state attenuates this direct effect by cooling down the cold tongue (-0.10°C/month). This rectified effect occurs through the TIW induced deepening and weakening of the Equatorial Undercurrent, that subsequently modulates the mean zonal advection and counterbalances TIWs direct effect. This approach allows quantifying the rectified effect of TIWs without degrading the model horizontal resolution, and may lead to a better characterization of the eastern tropical Pacific mean state and to the development of TIW parameterizations in Earth system models.

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Assessing feedback of tropical instability wave‐induced wind stress perturbations in the equatorial Pacific

Cited by 6 publications

References 28 publications

Climate Perspectives in the Intra–Americas Seas

Climate Perspectives in the Intra–Americas Seas

An Empirical Tropical Instability Wave-induced Wind Stress Model in the Equatorial Pacific and its Incorporation into the Ocean Model

Direct and Rectified Effects of Tropical Instability Waves on the Eastern Tropical Pacific Mean State in a Regional Ocean Model

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