Instantaneous Linkages between Clouds and Large-Scale Meteorology over the Southern Ocean in Observations and a Climate Model

Wall, Casey J.; Hartmann, Dennis L.; Ma, Po‐Lun

doi:10.1175/jcli-d-17-0156.1

Cited by 41 publications

(42 citation statements)

References 75 publications

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“…Over the Southern Ocean, locations with ascending motion in the CTL run are associated with a deep cloud layer with two relative maxima in cloud fraction near 400 hPa and 850 hPa (Figure a), consistent with observed vertical profiles of clouds in ascending regions of SH extratropical cyclones (Govekar et al, ; Wall et al, ). In contrast, locations with descending motion in the CTL run are associated with a shallow cloud layer below 700–850 hPa and little cloud fraction above, consistent with the observed prevalence of low cloud decks over subsiding regions of the Southern Ocean (Haynes et al, ).…”

Section: Resultssupporting

confidence: 84%

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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Section: Resultssupporting

confidence: 84%

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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“…Bodas-Salcedo et al (2012) show that cloud regimes occupy distinct regions in the warm and cold sectors of the cyclone composite. Naud et al (2006) show that vertical pressure velocity at 500 hPa ( 500 ) provides a very good discrimination between the warm ( 500 < 0) and cold sectors ( 500 > 0) of the cyclone composite, also corroborated by a recent study (Wall et al, 2017). We therefore use 500 as a compositing variable to gain insight in the relationships between clouds and radiation in the midlatitudes.…”

Section: Methodssupporting

confidence: 66%

Cloud Condensate and Radiative Feedbacks at Midlatitudes in an Aquaplanet

Bodas‐Salcedo

2018

Geophysical Research Letters

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Climate models show a robust negative feedback in the midlatitudes, coincident with an increase in cloud liquid in the mixed‐phase region of the control climate. This “mixed‐phase feedback” is normally attributed to a feedback caused by a phase change feedback (ice to liquid). Here we use an aquaplanet configuration to investigate this in more detail. We use high‐frequency instantaneous diagnostics and composite them in ascending and descending regimes. We find that a large fraction of the increase in cloud liquid water in the mixed‐phase region does not significantly contribute to the radiative feedback due to a masking effect of the ice cloud above. Using some simple arguments and approximate calculations, we estimate that about one third of the total shortwave negative radiative feedback is driven by a phase change feedback, whereas the rest of the feedback is driven by changes in ice and warm liquid clouds.

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“… Note . The corresponding results of Wall et al () are shown for comparison. SST = sea surface temperature, EIS = estimated inversion strength.…”

Section: Discussionmentioning

confidence: 90%

Cloud Heterogeneity in the Marine Midlatitudes: Dependence on Large‐Scale Meteorology and Implications for General Circulation Models

Loveridge

Davies

2019

JGR Atmospheres

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We examine the sensitivity of cloud heterogeneity to large‐scale meteorology in the marine midlatitudes using satellite observations from the Multiangle Imaging Spectroradiometer and Moderate Resolution Imaging Spectroradiometer instruments aboard the Terra satellite and nudged simulations from the UK Met Office's Global Atmosphere 7.0 (GA7) for the year 2007. Using Multiangle Imaging Spectroradiometer observations, we quantify several sources of observational uncertainty due to cloud heterogeneity such as finite‐resolution cloud fraction biases and subpixel heterogeneity. With a simple measure of cloud geometry, we show that these sources of observational uncertainty are maximized in post–cold‐frontal conditions, where scattered subpixel clouds are frequent, and are minimized in the warm sector, where subpixel clouds are infrequent. These results demonstrate the greater difficulty in interpreting remote sensing measurements in post–cold‐frontal conditions compared to quiescent or warm‐sector conditions. We show that the neglect of this observational uncertainty can qualitatively alter the interpretation of how cloud properties respond to large‐scale meteorology in GA7 and general circulation models in general. However, conservative application of the satellite data still allows robust evaluation of the simulated clouds. For overcast domains, Moderate Resolution Imaging Spectroradiometer observations show that overcast cloud heterogeneity is independent of large‐scale meteorology. However, heterogeneity increases when moving from warm sector to post‐cold‐frontal conditions in GA7. GA7 overestimates the heterogeneity of the low‐topped clouds that populate these regimes. For overcast domains, this bias is equivalent to a 15% underestimation in the mean cloud optical depth. These results suggest a systematic error in the subgrid‐scale variability parameterization, which, when corrected, will improve the simulation of the midlatitudes in GA7.

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Instantaneous Linkages between Clouds and Large-Scale Meteorology over the Southern Ocean in Observations and a Climate Model

Cited by 41 publications

References 75 publications

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

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

Cloud Condensate and Radiative Feedbacks at Midlatitudes in an Aquaplanet

Cloud Heterogeneity in the Marine Midlatitudes: Dependence on Large‐Scale Meteorology and Implications for General Circulation Models

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