Cloud Radiative Feedbacks and El Niño–Southern Oscillation

Middlemas, E.; Clement, A. C.; Medeiros, Brian; Kirtman, Ben P.

doi:10.1175/jcli-d-18-0842.1

Cited by 42 publications

(46 citation statements)

References 55 publications

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“…Cloud locking has been implemented and scientifically validated within CESM1‐CAM5 (Middlemas et al, 2019). To “lock” the clouds in CESM1‐CAM5, 10 cloud parameters are prescribed in the radiation calculations of the atmospheric model.…”

Section: Methodsmentioning

confidence: 99%

Quantifying the Influence of Cloud Radiative Feedbacks on Arctic Surface Warming Using Cloud Locking in an Earth System Model

Middlemas

Kay

Medeiros

et al. 2020

Geophysical Research Letters

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Understanding the influence of clouds on amplified Arctic surface warming remains an important unsolved research problem. Here, this cloud influence is directly quantified by disabling cloud radiative feedbacks or “cloud locking” within a state‐of‐the‐art and well‐documented model. Through comparison of idealized greenhouse warming experiments with and without cloud locking, the influence of Arctic and global cloud feedbacks is assessed. Global cloud feedbacks increase both global and Arctic warming by around 25%. In contrast, disabling Arctic cloud feedbacks has a negligible influence on both Arctic and global surface warming. Interestingly, the sum of noncloud radiative feedbacks does not change with either global or Arctic‐only cloud locking. Notably, the influence of Arctic cloud feedbacks is likely underestimated, because, like many models, the model used here underestimates high‐latitude supercooled cloud liquid. More broadly, this work demonstrates the value of regional and global cloud locking in a well‐characterized model.

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Section: Methodsmentioning

confidence: 99%

Quantifying the Influence of Cloud Radiative Feedbacks on Arctic Surface Warming Using Cloud Locking in an Earth System Model

Middlemas

Kay

Medeiros

et al. 2020

Geophysical Research Letters

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“…We repeat the cloud-locking method described above in CESM1.2, except that the experiment length is 315 years, and the climatological SST change is small in the subtropical eastern ocean basins, so no flux adjustment is required. On the other hand, the El Niño Southern Oscillation responds dramatically to cloud-locking by a threefold magnitude increase and a shift to decadal timescales (Middlemas et al 2019), which dominates the global SST response. Because we are interested in the local energy budget determining SST variability in the subtropical eastern ocean basins, we remove teleconnections from El Niño Southern Oscillation in the fully-coupled simulation by subtracting the Niño3.4 index from every field through linear regression analysis (Chiang and Vimont 2004).…”

Section: Modeling Experimentsmentioning

confidence: 99%

Contributions of atmospheric and oceanic feedbacks to subtropical northeastern sea surface temperature variability

2019

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Previous studies show that the dominant mode of variability in the Northeastern subtropical Pacific and Atlantic are analogous. Most attention has been given to the wind-evaporation-sea surface temperature (WES) feedback, but more recent studies suggest that clouds and ocean play a role. Here, it is shown that, while the mode of variability is similar, the quantitative role of clouds and ocean are different. Using Community Earth System Model, version 1.2, cloud feedbacks and interactive ocean dynamics are disabled separately to diagnose the relative contributions of each to sea surface temperature (SST) variability in subtropical northeastern ocean basins. Results from four experiments show that the relative contributions from WES and cloud radiative feedback depend on the role of the ocean. Positive cloud radiative feedback is evident in both basins but has less impact on SST variance in the Atlantic than in the Pacific. The reason for this is that ocean processes strongly damp SST anomalies in the Pacific and weakly enhance SST anomalies in the Atlantic. When cloud feedbacks are disabled, ocean processes become a larger driver of SST variability in the Atlantic. In line with previous studies, the Northeast Pacific SST variability may be understood as a white-noise-forced linear stochastic system with positive feedback from cloud and damping by latent heat flux and ocean processes, while Atlantic SST is driven partially by variations in ocean circulation and requires vertical mixing for rendition. Between these two regions, different ocean dynamics lead to different roles for atmospheric feedbacks but still result in similar patterns of SST variability.

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“…By modifying the temporal variability of CRE (but maintaining the same mean state), several modeling experiments have shown that high‐frequency interactions among dynamics, clouds, and radiation significantly impact modes of climate variability in the tropics. Eliminating or altering the temporal evolution of CRE modifies the spectrum of equatorial waves (Zurovac‐Jevtić et al, ), the propagation of the Madden‐Julian Oscillation (Lee et al, ), and the amplitude and periodicity of the El Niño–Southern Oscillation (ENSO; Middlemas et al, ; Rädel et al, ).…”

Section: Introductionmentioning

confidence: 99%

Investigating the Influence of Cloud Radiative Effects on the Extratropical Storm Tracks

Grise

Medeiros

Benedict

et al. 2019

Geophysical Research Letters

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Recent studies have focused on the role of cloud radiative effects (CRE) in governing the mean atmospheric circulation and its response to climate change. This study instead examines the role of CRE in climate variability in the extratropics. Cloud locking experiments are performed using the Community Earth System Model. In these experiments, CRE are scrambled, such that they maintain the same climatology but no longer match the model's dynamical fields. The results of these experiments indicate that high‐frequency interactions between CRE and dynamics have a small (≤5–10%) but statistically significant damping effect on the intensity of the extratropical storm tracks, particularly in the Southern Hemisphere. Individual midlatitude cyclones have decreased intensity and shorter lifetime. These effects arise largely from clouds' radiative modification of static stability below 700 hPa. The coupling among clouds, radiation, and dynamics thus has a modest but potentially important influence on the extratropical storm tracks.

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Cloud Radiative Feedbacks and El Niño–Southern Oscillation

Cited by 42 publications

References 55 publications

Quantifying the Influence of Cloud Radiative Feedbacks on Arctic Surface Warming Using Cloud Locking in an Earth System Model

Quantifying the Influence of Cloud Radiative Feedbacks on Arctic Surface Warming Using Cloud Locking in an Earth System Model

Contributions of atmospheric and oceanic feedbacks to subtropical northeastern sea surface temperature variability

Investigating the Influence of Cloud Radiative Effects on the Extratropical Storm Tracks

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