Wintertime Synoptic Patterns of Midlatitude Boundary Layer Clouds Over the Western North Atlantic: Climatology and Insights From In Situ ACTIVATE Observations

Painemal, David; Chellappan, Seethala; Smith, William L.; Spangenberg, Douglas A.; Park, J. Minnie; Ackerman, Andrew S.; Chen, J.; Crosbie, Ewan; Ferrare, R. A.; Hair, Johnathan; Kirschler, Simon; Li, Xiang‐Yu; McComiskey, Allison; Moore, Richard H.; Sanchez, Kevin J.; Sorooshian, Armin; Tornow, Florian; Voigt, Christiane; Wang, Hailong; Winstead, Edward L.; Zeng, Xubin; Ziemba, Luke D.; Zuidema, Paquita

doi:10.1029/2022jd037725

Cited by 10 publications

(4 citation statements)

References 48 publications

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“…Differences between the upper ("top") and lower ("bottom") quarter of the boundary layer total water (ice+liquid+vapor mixing ratio; 𝑞 𝑡 ) and the ice-liquid water potential temperature The transition to lower-albedo cloud can occur via two pathways. In the five days examined here, the more intense CAOs, which typically occur earlier in the year (Painemal et al 2023), deepen more and sustain both more ice and more rain by the eastern GS edge, than do the less intense CAOs occurring later in the year. In the limited sample size examined here, precipitation reaching the surface only sets in after the CAO has reached the eastern GS edge and beyond.…”

Section: Evidence For Primary and Secondary Ice Productionmentioning

confidence: 74%

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Microphysical evolution in mixed-phase mid-latitude marine cold-air outbreaks

Zuidema,

Chellappan,

Kirschler

et al. 2023

Preprint

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Five cold-air outbreaks are investigated with aircraft offshore of continental northeast American. Flight paths aligned with the cloud-layer flow span cloud-top temperatures of -5 to -12 0C, in situ liquid water paths of up to 600 g m-2, while in situ cloud droplet number concentrations exceeding 500 cm-3 maintain effective radii below 10 micron. Ice is usually present at cloud initiation. Further downstream, ice particle number concentrations (N_i) of 0.1-2.5 L-1 indicate secondary ice production. This is enhanced near cloud top, consistent with collisional breakup of graupel and vapor-grown ice particles, and near cloud base, where ice aggregates near 0 0C. Rime-splintering is clearly evident. The highest ice water contents coincide with temperatures favoring dendritic growth. Warmer clouds and weaker surface fluxes correlate to fewer ice particles. Buoyancy fluxes reach 400-600 W m-2 near the Gulf Stream's western edge, with updrafts reaching five m s-1 supporting closely-spaced convective cells. Upper-level detrainment maintains a high overall cloud fraction despite decoupled boundary layer vertical structures. The near-surface liquid rainfall rates of three more intense cold-air outbreaks are a maximum near the Gulf Stream's eastern edge, just before the clouds transition to more open-celled structures, and correspond to higher cloud liquid water paths. The milder two cold-air outbreaks transition to lower-albedo cumulus through cloud thinning.

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Section: Evidence For Primary and Secondary Ice Productionmentioning

confidence: 74%

“…2, third row). As documented in Painemal et al (2023), the trough and trough-to-ridge portions of mid-latitude cyclones give rise to the coastal northerly winds and subsidence that support CAOs.…”

Section: Overviewmentioning

confidence: 95%

Microphysical evolution in mixed-phase mid-latitude marine cold-air outbreaks

Zuidema,

Chellappan,

Kirschler

et al. 2023

Preprint

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“…Over the western boundary current regions, surface turbulent fluxes are strong and SHF is the dominant CCF. For the Gulf Stream, the low‐cloud dominated conditions often are formed during cold air outbreaks (e.g., Painemal et al., 2023). In the Agulhas Return Current region, the influence of the SHF in the absence of strong EIS has been discussed previously for monthly data (Miyamoto et al., 2018), and our results affirm those findings for the daily timescale.…”

Section: Discussionmentioning

confidence: 99%

Dominant Cloud Controlling Factors for Low‐Level Cloud Fraction: Subtropical Versus Extratropical Oceans

Naud,

Elsaesser,

Booth

2023

Geophysical Research Letters

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To improve cloud feedback understanding and simulation, observations have been used to quantify the rate of change of cloud radiative properties as a function of specific environmental metrics (or cloud controlling factors; CCFs). The study focuses on low‐level cloud dominated regions during 2006–2010. For each ocean gridpoint, Spearman's rank correlation coefficients of daily mean observed cloud fraction versus (a) 10‐m wind, (b) sensible heat flux (SHF), (c) sea surface temperature, (d) estimated inversion strength (EIS), (e) 850 hPa vertical velocity, and (f) the M parameter () are sorted to identify the dominant CCFs in both extratropics (30°–60°N/S) and subtropics (30°S–30°N). A novel map for visualizing dominant CCFs for low‐level cloud fraction reveals that: dominates in the subtropical stratocumulus regions while 10‐m winds dominate in shallow cumulus regions but in the extratropics, a different inversion structure diagnostic (EIS) dominates, while SHF dominates in western boundary current areas.

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“…This absence of a coherent spatial correlation between the CAO index, surface heat fluxes, and N d lends further credence to our hypothesis that meteorological factors are not the predominant influence on N d trends. Furthermore, considering the positive correlation between the CAO index and low-cloud fraction (Naud et al, 2020;Painemal et al, 2023), the lack of significant trends in low-cloud fraction (Figure 4a) despite an increase in the CAO index over the Gulf Stream suggests the need for more in-depth study. Overall, our findings do not support the notion of meteorological dominance over N d variability.…”

Section: Large-scale Meteorologymentioning

confidence: 99%

Long‐Term Trends in Aerosols, Low Clouds, and Large‐Scale Meteorology Over the Western North Atlantic From 2003 to 2020

Park,

McComiskey,

Painemal

et al. 2024

JGR Atmospheres

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A continuous decrease in aerosols over the Western North Atlantic Ocean (WNAO) on a decadal timescale provides a long‐term benchmark to evaluate how various natural and anthropogenic processes affect the manifestation of aerosol‐cloud interactions in this region. Furthermore, the WNAO serves as a natural laboratory with diverse aerosol sources, marine boundary layer clouds more variable than those in marine stratocumulus deck regions, and unique flow regimes established by the Gulf Stream and the semi‐permanent Bermuda High. We investigate how satellite‐retrieved macrophysical and microphysical properties of low clouds and the surface shortwave irradiance changed from 2003 to 2020, in tandem with this aerosol decrease. The decadal changes in large‐scale meteorology related to the North Atlantic Oscillation (NAO) are also examined. We find a reduction in low‐cloud optical thickness, accompanied by fewer and larger cloud droplets, yet observe no significant changes in low‐cloud fraction and liquid water path. Despite the reduction in low‐cloud optical thickness together with aerosol decrease, a corresponding increase in the trends of surface shortwave irradiance, also known as surface brightening, is lacking. This absence of brightening is potentially related to concomitant changes found in large‐scale meteorology associated with NAO—Bermuda High strengthening, sea surface warming, and atmospheric moistening— as well as an increase in high‐level cloud fraction that can counteract the surface brightening. Ultimately, our findings suggest that spatial patterns of decadal meteorological variability introduce complexities in the surface cloud radiative effect over the WNAO, thereby complicating the isolation and examination of aerosol‐cloud interactions.

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Wintertime Synoptic Patterns of Midlatitude Boundary Layer Clouds Over the Western North Atlantic: Climatology and Insights From In Situ ACTIVATE Observations

Cited by 10 publications

References 48 publications

Microphysical evolution in mixed-phase mid-latitude marine cold-air outbreaks

Microphysical evolution in mixed-phase mid-latitude marine cold-air outbreaks

Dominant Cloud Controlling Factors for Low‐Level Cloud Fraction: Subtropical Versus Extratropical Oceans

Long‐Term Trends in Aerosols, Low Clouds, and Large‐Scale Meteorology Over the Western North Atlantic From 2003 to 2020

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