Extratropical–Tropical Interaction Model Intercomparison Project (Etin-Mip): Protocol and Initial Results

Kang, Sarah M.; Hawcroft, Matt; Xiang, Baoqiang; Hwang, Yean Ren; Cazes, Gabriel; Codron, Francis; Crueger, Traute; Deser, Clara; Hodnebrog, Øivind; Kim, Hanjun; Kim, Jiyeong; Kosaka, Yu; Losada, Teresa; Mechoso, Carlos R.; Myhre, Gunnar; Seland, Øyvind; Stevens, Björn; Watanabe, Masahiro; Yu, Sungduk

doi:10.1175/bams-d-18-0301.1

Cited by 33 publications

(9 citation statements)

References 75 publications

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“…All SOM experiments are integrated for 100 years, and the last 40 years are used for the analysis. The experiment setup in this study is the protocol used for ETIN-MIP ( 22 ) so that the results from nine independent fully coupled models are overlaid with the DOM experiment results in Fig. 3A and figs.…”

Section: Methodsmentioning

confidence: 99%

“…To investigate the dynamical pathways in different components of the climate system, we use an atmospheric general circulation model coupled with a hierarchy of ocean models, ranging from a SOM on an idealized aquaplanet (AQUA) or a realistic continental configuration to a full dynamical ocean model (DOM) (Materials and Methods). The DOM experiments are part of the Extratropical-Tropical Interaction Model Intercomparison Project (ETIN-MIP) ( 22 ), allowing us to examine the robustness of the DOM experiments through the analysis of nine independent fully coupled model simulations. The SOM experiments are conducted with two independent models to examine model uncertainty.…”

Section: Introductionmentioning

confidence: 99%

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Walker circulation response to extratropical radiative forcing

et al. 2020

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Walker circulation variability and associated zonal shifts in the heating of the tropical atmosphere have far-reaching global impacts well into high latitudes. Yet the reversed high latitude–to–Walker circulation teleconnection is not fully understood. Here, we reveal the dynamical pathways of this teleconnection across different components of the climate system using a hierarchy of climate model simulations. In the fully coupled system with ocean circulation adjustments, the Walker circulation strengthens in response to extratropical radiative cooling of either hemisphere, associated with the upwelling of colder subsurface water in the eastern equatorial Pacific. By contrast, in the absence of ocean circulation adjustments, the Walker circulation response is sensitive to the forcing hemisphere, due to the blocking effect of the northward-displaced climatological intertropical convergence zone and shortwave cloud radiative effects. Our study implies that energy biases in the extratropics can cause pronounced changes of tropical climate patterns.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Walker circulation response to extratropical radiative forcing

et al. 2020

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“…Hwang et al. (2017) attributed the zonal asymmetry in the tropical South Pacific SST response to wind‐evaporation‐SST (WES) and shortwave cloud feedbacks, while ocean dynamics play an additional role in coupled models (Kang et al., 2019). Here, we show that the same processes contribute to the SST response in the tropical South Atlantic to the observed SO cooling.…”

Section: Introductionmentioning

confidence: 99%

“…SO SST variability resulting from open-ocean convection in Weddell Sea has a significant impact on global energy balance redistribution, affecting tropical SSTs and precipitation (Cabré et al, 2017). Idealized studies have explored the effects of SO SST cooling, which often extends into the tropical southeastern Pacific and Atlantic (Hwang et al, 2017;Kang et al, 2019), reducing the warm SST biases in those regions (Mechoso et al, 2016 Stippling indicates local trend that is significant at or above 95% level. Black lines outline the SST nudging domain.…”

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confidence: 99%

Is There a Tropical Response to Recent Observed Southern Ocean Cooling?

Zhang

Deser

Sun

2021

Geophysical Research Letters

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Despite global warming, SSTs in the Southern Ocean (SO) have cooled in recent decades largely as a result of internal variability. The global impact of this cooling is assessed by nudging evolving SO SST anomalies to observations in an ensemble of coupled climate model simulations under historical radiative forcing, and comparing against a control ensemble. The most significant remote response to observed SO cooling is found in the tropical South Atlantic, where increased clouds and strengthened trade winds cool the sea surface, partially offsetting the radiatively forced warming trend. The SO ensemble produces a more realistic tropical South Atlantic SST trend, and exhibits a higher pattern correlation with observed SST trends in the greater Atlantic basin, compared to the control ensemble. SO cooling also produces a significant increase in Antarctic sea ice, but not enough to offset radiatively induced ice loss; thus, the SO ensemble remains biased in its sea ice trends.

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“…Understanding what controls ITCZ characteristics remains a fundamental question in climate science (Bony et al., 2015) and has motivated several model intercomparison projects including prescribed‐SST aquaplanet simulations in CMIP5 (Coupled Model Intercomparison Project Phase 5; Voigt & Shaw, 2015) and aquaplanet slab ocean simulations with a prescribed q flux in TRACMIP (Tropical Rain belts with an Annual cycle and a Continent; Voigt et al., 2016). Alongside these studies, ETIN‐MIP (Extratropical‐Tropical Interaction Model Intercomparison Project) uses state‐of‐the‐art coupled climate models to investigate model variability in the sensitivity of the ITCZ to variations in shortwave radiation forcing (Kang et al., 2019). As interactive OET reduces the sensitivity of the ITCZ to an atmospheric forcing or parameterization (Green & Marshall, 2017; Tomas et al., 2016), an idealized model intercomparison project with an interactive OET is planned (Kucharski et al., 2018), to investigate if an interactive OET changes the intermodel variability of the tropical circulation.…”

Section: Discussionmentioning

confidence: 99%

The Effect of Atmosphere‐Ocean Coupling on the Sensitivity of the ITCZ to Convective Mixing

Talib

Woolnough

Klingaman

et al. 2020

J Adv Model Earth Syst

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The Intertropical Convergence Zone (ITCZ) is a discontinuous, zonal precipitation band that plays a crucial role in the global hydrological cycle. Previous studies using prescribed sea surface temperature (SST) aquaplanets show the ITCZ is sensitive to convective mixing, but such a framework is energetically inconsistent. Studies also show that atmosphere-ocean coupling reduces the sensitivity of the ITCZ to hemispherically asymmetric forcing. We investigate the effect of atmosphere-ocean coupling on the sensitivity of the ITCZ to convective mixing using an idealized modeling framework with an Ekman-driven ocean energy transport (OET). Coupling reduces the sensitivity of the ITCZ location to convective mixing due to SST changes. In prescribed-SST simulations reducing convective mixing promotes a double ITCZ, while in coupled simulations, it increases the meridional SST gradient which promotes an equatorward ITCZ shift. Prescribing OET in additional experiments has a minimal effect on the sensitivity of the ITCZ location to mixing but does increase the sensitivity of the ITCZ intensity by constraining the net-downward surface energy flux. Decreasing convective mixing increases net-downward shortwave cloudy-sky radiation associated with increased latent heat fluxes and an intensified ITCZ. For simulations analyzed the atmospheric energy input framework is inadequate to study ITCZ dynamics due to the contribution of transient eddies to the atmospheric energy transport. Prescribing SST or OET may strengthen the sensitivity of the ITCZ to a change in parameterization or atmospheric forcing. Future modeling studies investigating the precipitation response to such changes should be aware of the potential sensitivity of their results to atmosphere-ocean interactions. Plain Language Summary The Intertropical Convergence Zone (ITCZ) is a discontinuous tropical rainfall band with over three billion livelihoods dependent on its seasonal cycle. However, even the latest state-of-the-art climate models poorly simulate the real-world ITCZ. Previous modeling studies which fix sea surface temperatures and have no land show that the ITCZ is sensitive to the model's representation of deep clouds. However, it is yet to be determined whether ocean dynamics that are influenced by the atmosphere removes this sensitivity. In this study we couple the atmosphere to an ocean model with a circulation that depends on near-surface winds. Through doing so we highlight that interactions between the atmosphere and ocean reduce changes in ITCZ location when varying the representation of deep clouds. This is predominately associated with sea surface temperature changes rather than changes in ocean circulation. However, fixing the ocean circulation and only allowing sea surface temperatures to vary, can cause different changes in ITCZ intensity when changing the representation of deep clouds. We therefore highlight that fixing either sea surface temperatures or the ocean circulation can affect how the ITCZ responds to changes in model design.

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Extratropical–Tropical Interaction Model Intercomparison Project (Etin-Mip): Protocol and Initial Results

Abstract: ETIN-MIP is a community-wide effort to improve dynamical understanding of the linkages between tropical precipitation and radiative biases in various regions, with implications for anthropogenic climate change and geoengineering.

Cited by 33 publications

References 75 publications

Walker circulation response to extratropical radiative forcing

Walker circulation response to extratropical radiative forcing

Is There a Tropical Response to Recent Observed Southern Ocean Cooling?

The Effect of Atmosphere‐Ocean Coupling on the Sensitivity of the ITCZ to Convective Mixing

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