Circus Tents, Convective Thresholds, and the Non‐Linear Climate Response to Tropical SSTs

Williams, Andrew; Jeevanjee, Nadir; Bloch‐Johnson, Jonah

doi:10.1029/2022gl101499

Cited by 17 publications

(13 citation statements)

References 57 publications

(92 reference statements)

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“…On the other hand, the cold MAM WTA SSTA had a limited tropospheric temperature response (Figure 4b), consistent with the results of Williams et al. (2023) which showed a weaker convection response for cold SST anomalies. The Rossby wave‐like patterns straddling the equator were detected for the cold WTA, but the Kelvin wave‐like eastward extension was not evident compared to the warm WTA case (cf.…”

Section: Mechanism For An Asymmetric Response From Atlantic Sstassupporting

confidence: 90%

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The Tropical Atlantic's Asymmetric Impact on the El Niño‐Southern Oscillation

van Rensch,

McGregor,

Dommenget

et al. 2024

Geophysical Research Letters

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Using observations and Atlantic forced coupled model simulations, we show evidence for an asymmetry in the link between beginning of year tropical Atlantic sea surface temperature anomalies (SSTAs) and end of the year El Niño‐Southern Oscillation events. We find a greater tendency for warm Atlantic SSTAs to lead to a La Niña than for cold anomalies to lead to El Niño. The model experiments showed that the Atlantic had a greater chance to force the tropical Pacific if the Pacific was initially in a neutral state. In the model, a warm Atlantic from March–May was able to produce an atmospheric response leading to easterly wind anomalies in the western Pacific. This in turn induces a subsurface oceanic response, leading to La Niña at the end of the year. The atmospheric response does not occur for a cold Atlantic, leading to no impacts in the Pacific.

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Section: Mechanism For An Asymmetric Response From Atlantic Sstassupporting

confidence: 90%

“…It has been shown that cold SSTAs produce a weaker magnitude global atmospheric response compared to their opposite warm SSTAs (Williams et al., 2023). Whether this asymmetry in response can occur in the Atlantic has begun to be explored.…”

Section: Introductionmentioning

confidence: 99%

The Tropical Atlantic's Asymmetric Impact on the El Niño‐Southern Oscillation

van Rensch,

McGregor,

Dommenget

et al. 2024

Geophysical Research Letters

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“…All of these nonlinearities may have a common explanation, proposed by Williams et al (2023), which documented similar nonlinearities with the ICON model. In order to set off deep convection, the surface conditions of tropical regions must reach a threshold in which their subcloud moist static energy is larger than the saturated moist static energy aloft (Williams & Pierrehumbert, 2017).…”

Section: ∂N/∂sstmentioning

confidence: 55%

The Green's Function Model Intercomparison Project (GFMIP) Protocol

Bloch‐Johnson,

Rugenstein,

Alessi

et al. 2024

J Adv Model Earth Syst

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The atmospheric Green's function method is a technique for modeling the response of the atmosphere to changes in the spatial field of surface temperature. While early studies applied this method to changes in atmospheric circulation, it has also become an important tool to understand changes in radiative feedbacks due to evolving patterns of warming, a phenomenon called the “pattern effect.” To better study this method, this paper presents a protocol for creating atmospheric Green's functions to serve as the basis for a model intercomparison project, GFMIP. The protocol has been developed using a series of sensitivity tests performed with the HadAM3 atmosphere‐only general circulation model, along with existing and new simulations from other models. Our preliminary results have uncovered nonlinearities in the response of the atmosphere to surface temperature changes, including an asymmetrical response to warming versus cooling patch perturbations, and a change in the dependence of the response on the magnitude and size of the patches. These nonlinearities suggest that the pattern effect may depend on the heterogeneity of warming as well as its location. These experiments have also revealed tradeoffs in experimental design between patch size, perturbation strength, and the length of control and patch simulations. The protocol chosen on the basis of these experiments balances scientific utility with the simulation time and setup required by the Green's function approach. Running these simulations will further our understanding of many aspects of atmospheric response, from the pattern effect and radiative feedbacks to changes in circulation, cloudiness, and precipitation.

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“…For example, estimates of EffCS from the observed historical energy budget constraints are lower than those from long‐term warming under CO 2 quadrupling, primarily owing to changes in the tropical Pacific SST patterns (Andrews et al., 2018, 2022; Dong et al., 2019; Gregory et al., 2020; Zhou et al., 2016). This “pattern effect” has been studied with a Green's function approach (Dong et al., 2019; Zhang et al., 2023; Zhou et al., 2017), which shows that the global feedback has a predominant dependence on tropical convective regions (Williams et al., 2023), and is less sensitive to the North Atlantic SSTs. This tropical Pacific SST pattern effect has been found to be a leading mechanism for the time evolution of EffCS estimates.…”

Section: Discussionmentioning

confidence: 99%

Non‐Monotonic Feedback Dependence Under Abrupt CO₂ Forcing Due To a North Atlantic Pattern Effect

Mitevski

Dong

Polvani

et al. 2023

Geophysical Research Letters

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Effective climate sensitivity (EffCS), commonly estimated from model simulations with abrupt 4×CO2 for 150 years, has been shown to depend on the CO2 forcing level. To understand this dependency systematically, we performed a series of simulations with a range of abrupt CO2 forcing in two climate models. Our results indicate that normalized EffCS values in these simulations are a non‐monotonic function of the CO2 forcing, decreasing between 3× and 4×CO2 in CESM1‐LE (2× and 3×CO2 in GISS‐E2.1‐G) and increasing at higher CO2 levels. The minimum EffCS value, caused by anomalously negative radiative feedbacks, arises mainly from sea‐surface temperature (SST) relative cooling in the tropical and subtropical North Atlantic. This cooling is associated with the formation of the North Atlantic Warming Hole and Atlantic Meridional Overturning Circulation collapse under CO2 forcing. Our findings imply that understanding changes in North Atlantic SST patterns is important for constraining near‐future and equilibrium global warming.

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Circus Tents, Convective Thresholds, and the Non‐Linear Climate Response to Tropical SSTs

Cited by 17 publications

References 57 publications

The Tropical Atlantic's Asymmetric Impact on the El Niño‐Southern Oscillation

The Tropical Atlantic's Asymmetric Impact on the El Niño‐Southern Oscillation

The Green's Function Model Intercomparison Project (GFMIP) Protocol

Non‐Monotonic Feedback Dependence Under Abrupt CO₂ Forcing Due To a North Atlantic Pattern Effect

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Circus Tents, Convective Thresholds, and the Non‐Linear Climate Response to Tropical SSTs

Cited by 17 publications

References 57 publications

The Tropical Atlantic's Asymmetric Impact on the El Niño‐Southern Oscillation

The Tropical Atlantic's Asymmetric Impact on the El Niño‐Southern Oscillation

The Green's Function Model Intercomparison Project (GFMIP) Protocol

Non‐Monotonic Feedback Dependence Under Abrupt CO2 Forcing Due To a North Atlantic Pattern Effect

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Product

Resources

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Non‐Monotonic Feedback Dependence Under Abrupt CO₂ Forcing Due To a North Atlantic Pattern Effect