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  • 1
    Online Resource
    Online Resource
    The Barbados Cloud Observatory: Anchoring Investigations of Clouds and Circulation on the Edge of the ITCZ
    American Meteorological Society ; 2016
    In:  Bulletin of the American Meteorological Society Vol. 97, No. 5 ( 2016-05-01), p. 787-801
    Details
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 97, No. 5 ( 2016-05-01), p. 787-801
    Abstract: Clouds over the ocean, particularly throughout the tropics, are poorly understood and drive much of the uncertainty in model-based projections of climate change. In early 2010, the Max Planck Institute for Meteorology and the Caribbean Institute for Meteorology and Hydrology established the Barbados Cloud Observatory (BCO) on the windward edge of Barbados. At 13°N the BCO samples the seasonal migration of the intertropical convergence zone (ITCZ), from the well-developed winter trades dominated by shallow cumulus to the transition to deep convection as the ITCZ migrates northward during boreal summer. The BCO is also well situated to observe the remote meteorological impact of Saharan dust and biomass burning. In its first six years of operation, and through complementary intensive observing periods using the German High Altitude and Long Range Research Aircraft (HALO), the BCO has become a cornerstone of efforts to understand the relationship between cloudiness, circulation, and climate change.
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    URL: Article
    URL: Article
    DOI: 10.1175/BAMS-D-14-00247.1
    DOI: 10.1175/BAMS-D-14-00247.2
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 2
    Online Resource
    Online Resource
    The Influence of Wind Speed on Shallow Marine Cumulus Convection
    American Meteorological Society ; 2012
    In:  Journal of the Atmospheric Sciences Vol. 69, No. 1 ( 2012-01-01), p. 168-184
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 69, No. 1 ( 2012-01-01), p. 168-184
    Abstract: The role of wind speed on shallow marine cumulus convection is explored using large-eddy simulations and concepts from bulk theory. Focusing on cases characteristic of the trades, the equilibrium trade wind layer is found to be deeper at stronger winds, with larger surface moisture fluxes and smaller surface heat fluxes. The opposing behavior of the surface fluxes is caused by more warm and dry air being mixed to the surface as the cloud layer deepens. This leads to little difference in equilibrium surface buoyancy fluxes and cloud-base mass fluxes. Shallow cumuli are deeper, but not more numerous or more energetic. The deepening response is necessary to resolve an inconsistency in the subcloud layer. This argument follows from bulk concepts and assumes that the lapse rate and flux divergence of moist-conserved variables do not change, based on simulation results. With that assumption, stronger winds and a fixed inversion height imply larger surface moisture and buoyancy fluxes (heat fluxes are small initially). The consequent moistening tends to decrease cloud-base height, which is inconsistent with a larger surface buoyancy flux that tends to increase cloud-base height, in order to maintain the buoyancy flux at cloud base at a fixed fraction of its surface value (entrainment closure). Deepening the cloud layer by increasing the inversion height resolves this inconsistency by allowing the surface buoyancy flux to remain constant without further moistening the subcloud layer. Because this explanation follows from simple bulk concepts, it is suggested that the internal dynamics (mixing) of clouds is only secondary to the deepening response.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-11-02.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2012
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    On the Seasonal and Synoptic Time-Scale Variability of the North Atlantic Trade Wind Region and Its Low-Level Clouds
    American Meteorological Society ; 2015
    In:  Journal of the Atmospheric Sciences Vol. 72, No. 4 ( 2015-04-01), p. 1428-1446
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 72, No. 4 ( 2015-04-01), p. 1428-1446
    Abstract: The seasonality in large-scale meteorology and low-level cloud amount (CClow) is explored for a 5° × 5° area in the North Atlantic trades, using 12 years of ERA-Interim and MODIS data, supported by 2 years of Barbados Cloud Observatory (BCO) measurements. From boreal winter to summer, large-scale subsiding motion changes to rising motion, along with an increase in sea surface temperature, a clockwise turning and weakening of low-level winds, and reduced cold-air advection, lower-tropospheric stability (LTS), and surface fluxes. However, CClow is relatively invariant around 30%, except for a minimum of 20% in fall. This minimum is only pronounced when MODIS scenes with large high-level cloud amount are excluded, and a winter maximum in CClow is more pronounced at the BCO. On monthly time scales, wind speed has the best correlation with CClow. Existing large-eddy simulations suggest that the wind speed–CClow correlation may be explained by a direct deepening response of the trade wind layer to stronger winds. Large correlations of wind direction and advection with CClow also suggest that large-scale flow patterns matter. Smaller correlations with CClow are observed for LTS and surface evaporation, as well as negligible correlations for relative humidity (RH) and vertical velocity. However, these correlations considerably increase when only summer is considered. On synoptic time scales, all correlations drop substantially, whereby wind speed, RH, and surface sensible heat flux remain the leading parameters. The lack of a single strong predictor emphasizes that the combined effect of parameters is necessary to explain variations in CClow in the trades.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-14-0054.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2015
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Momentum Transport in Organized Shallow Cumulus Convection
    American Meteorological Society ; 2024
    In:  Journal of the Atmospheric Sciences Vol. 81, No. 2 ( 2024-02), p. 279-296
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 81, No. 2 ( 2024-02), p. 279-296
    Abstract: This study investigates momentum transport in shallow cumulus clouds as simulated with the Dutch Atmospheric Large Eddy Simulation (DALES) for a 150 × 150 km 2 domain east of Barbados during 9 days of EUREC 4 A. DALES is initialized and forced with the mesoscale weather model HARMONIE–AROME and subjectively reproduces observed cloud patterns. This study examines the evolution of momentum transport, which scales contribute to it, and how they modulate the trade winds. Daily-mean momentum flux profiles show downgradient zonal momentum transport in the subcloud layer, which turns countergradient in the cloud layer. The meridional momentum transport is nontrivial, with mostly downgradient transport throughout the trade wind layer except near the top of the surface layer and near cloud tops. Substantial spatial and temporal heterogeneity in momentum flux is observed with much stronger tendencies imposed in areas of organized convection. The study finds that while scales 〈 2 km dominate momentum flux at 200 m in unorganized fields, submesoscales carry up to 50% of the zonal momentum flux in the cloud layer in organized fields. For the meridional momentum flux, this fraction is even larger near the surface and in the subcloud layer. The scale dependence of the momentum flux is not explained by changes in convective or boundary layer depth. Instead, the results suggest the importance of spatial heterogeneity, increasing horizontal length scales, and countergradient transport in the presence of organized convection.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    URL: Article
    DOI: 10.1175/JAS-D-23-0098.1
    DOI: 10.1175/JAS-D-23-0098.s1
    RVK:
    UA 4800
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2024
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 5
    Online Resource
    Online Resource
    Influence of deepening and mesoscale organization of shallow convection on stratiform cloudiness in the downstream trades
    Wiley ; 2020
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 146, No. 726 ( 2020-01), p. 174-185
    Details
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 146, No. 726 ( 2020-01), p. 174-185
    Abstract: In this study we use large‐eddy simulation to explore the factors controlling stratiform cloudiness in the downstream trades. We perform sensitivity experiments with different large‐scale forcings, radiation specifications and domain sizes, which isolate the influence of convective deepening, moisture–radiation interactions and mesoscale organization, respectively. Across the simulations with different large‐scale forcings, we find that the deepening of the cloud layer and the associated increase in precipitation strongly correlate with decreasing inversion strength and stratiform cloudiness. The relationship between cloud‐layer depth and cloud amount is largely independent of the way a specific change in the large‐scale forcing induces the deepening. The interaction of radiation with the domain‐averaged humidity and cloud profile is necessary for stratiform cloudiness to form. Strong radiative cooling experienced by updraughts overshooting a strong inversion induces the formation of detrained stratiform layers, and strong long‐wave cooling associated with the stratiform layers stabilizes the inversion. Interactive radiation is also important for exposing differences in shallow convection under different free‐tropospheric humidities. A drier initial free troposphere leads to both increased cloud‐layer and free‐tropospheric radiative cooling and increased surface evaporation, which forces deeper convection and more precipitation compared to a moister initial free troposphere. The simulations with a drier initial free troposphere thus have weaker inversions and less stratiform cloud. The organization of convection into larger clusters in large‐domain simulations increases precipitation and weakens the inversion compared to a simulation on a 16‐fold smaller domain, which does not support convective organization. Organized updraught clusters carry more moisture and liquid to the inversion, so that the same amount of stratiform cloudiness forms, despite the inversion being weaker. The simulations presented here suggest that the deepening and organization of shallow convection plays an important role in regulating stratiform cloudiness and thus total cloud cover in the downstream trades.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    URL: Article
    DOI: 10.1002/qj.v146.726
    DOI: 10.1002/qj.3664
    RVK:
    UA 1000
    RVK:
    UA 7650
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    EUREC〈sup〉4〈/sup〉A
    Copernicus GmbH ; 2021
    In:  Earth System Science Data Vol. 13, No. 8 ( 2021-08-25), p. 4067-4119
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 13, No. 8 ( 2021-08-25), p. 4067-4119
    Abstract: Abstract. The science guiding the EUREC4A campaign and its measurements is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement.
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    DOI: 10.5194/essd-13-4067-2021
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2475469-9
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  • 7
    Online Resource
    Online Resource
    Observed and modeled patterns of covariability between low‐level cloudiness and the structure of the trade‐wind layer
    American Geophysical Union (AGU) ; 2015
    In:  Journal of Advances in Modeling Earth Systems Vol. 7, No. 4 ( 2015-12), p. 1741-1764
    Details
    In: Journal of Advances in Modeling Earth Systems, American Geophysical Union (AGU), Vol. 7, No. 4 ( 2015-12), p. 1741-1764
    Abstract: Models reveal unrealistic variability in cloudiness at short‐time scales Models overestimate variations in cloudiness near the LCL with RH and temperature lapse rates Models underestimate relationships that matter for cloudiness near the inversion on long‐time scales
    Type of Medium: Online Resource
    ISSN: 1942-2466 , 1942-2466
    URL: Issue
    URL: Article
    DOI: 10.1002/jame.v7.4
    DOI: 10.1002/2015MS000483
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2015
    detail.hit.zdb_id: 2462132-8
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  • 8
    Online Resource
    Online Resource
    The role of precipitation and spatial organization in the response of trade‐wind clouds to warming
    American Geophysical Union (AGU) ; 2016
    In:  Journal of Advances in Modeling Earth Systems Vol. 8, No. 2 ( 2016-06), p. 843-862
    Details
    In: Journal of Advances in Modeling Earth Systems, American Geophysical Union (AGU), Vol. 8, No. 2 ( 2016-06), p. 843-862
    Abstract: Cloud cover and albedo reduce only slightly with warming, demonstrating the robustness of shallow cumuli Precipitation prevents warmer cloud layer from deepening and relative drying Strong sensitivity of trade‐wind boundary layer to presence of deeper convection
    Type of Medium: Online Resource
    ISSN: 1942-2466 , 1942-2466
    URL: Issue
    URL: Article
    DOI: 10.1002/jame.v8.2
    DOI: 10.1002/2015MS000568
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2016
    detail.hit.zdb_id: 2462132-8
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  • 9
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    Online Resource
    Boundary Layer Clouds and Convection over Subtropical Oceans in our Current and in a Warmer Climate
    Springer Science and Business Media LLC ; 2019
    In:  Current Climate Change Reports Vol. 5, No. 2 ( 2019-6), p. 80-94
    Details
    In: Current Climate Change Reports, Springer Science and Business Media LLC, Vol. 5, No. 2 ( 2019-6), p. 80-94
    Type of Medium: Online Resource
    ISSN: 2198-6061
    URL: Article
    DOI: 10.1007/s40641-019-00126-x
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 2808618-1
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  • 10
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    Online Resource
    Clouds at Barbados are representative of clouds across the trade wind regions in observations and climate models
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 22 ( 2016-05-31)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 22 ( 2016-05-31)
    Abstract: Trade wind regions cover most of the tropical oceans, and the prevailing cloud type is shallow cumulus. These small clouds are parameterized by climate models, and changes in their radiative effects strongly and directly contribute to the spread in estimates of climate sensitivity. This study investigates the structure and variability of these clouds in observations and climate models. The study builds upon recent detailed model evaluations using observations from the island of Barbados. Using a dynamical regimes framework, satellite and reanalysis products are used to compare the Barbados region and the broader tropics. It is shown that clouds in the Barbados region are similar to those across the trade wind regions, implying that observational findings from the Barbados Cloud Observatory are relevant to clouds across the tropics. The same methods are applied to climate models to evaluate the simulated clouds. The models generally capture the cloud radiative effect, but underestimate cloud cover and show an array of cloud vertical structures. Some models show strong biases in the environment of the Barbados region in summer, weakening the connection between the regional biases and those across the tropics. Even bearing that limitation in mind, it is shown that covariations of cloud and environmental properties in the models are inconsistent with observations. The models tend to misrepresent sensitivity to moisture variations and inversion characteristics. These model errors are likely connected to cloud feedback in climate projections, and highlight the importance of the representation of shallow cumulus convection.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1521494113
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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