First measurements of ocean and atmosphere in the <scp>T</scp>ropical <scp>N</scp>orth <scp>A</scp>tlantic using <i><scp>C</scp>aravela</i>, a novel uncrewed surface vessel

Siddle, Elizabeth; Heywood, Karen J.; Webber, Benjamin G. M.; Bromley, Peter T.

doi:10.1002/wea.4004

Cited by 5 publications

(4 citation statements)

References 11 publications

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“… 50 , 51 ). For the SST, we extrapolate the 2-m-depth SST of the RV Meteor (thermosalinograph primary backboard temperature), or alternatively from the AutoNaut Caravela 52 , to the dropsonde location based on a fixed zonal and meridional SST gradient of −0.14 K per degree. A gradient of −0.14 K per degree corresponds to the median zonal and meridional gradient (−0.145 K per degree and −0.135 K per degree, respectively) across the EUREC 4 A circle over the period from 19 January to 15 February in the ERA5 reanalysis 53 and in two satellite SST products (from the Advanced Baseline Imager on board the Geostationary Operational Environmental Satellite (GOES-16 ABI) and the Collecte Localisation Satellites (CLS).…”

Section: Methodsmentioning

confidence: 99%

“…The estimation uncertainty of the surface buoyancy flux is a combination of uncertainty in the underlying SSTs and in the COARE bulk flux algorithm. We estimate the uncertainty in the underlying SSTs by computing the SE of five different versions of the flux (three with different fixed SST gradients (the default median value and the median ± interquartile range, that is, −0.14 K per degree, −0.21 K per degree and −0.07 K per degree), one with a temporally varying gradient (not shown) and one with a different baseline SST (from the AutoNaut Caravela 52 instead of the RV Meteor)) and adding a 5% uncertainty of the COARE algorithm given in ref. 50 as the 1-h uncertainty in the 0–10 m s −1 wind speed range.…”

Section: Methodsmentioning

confidence: 99%

“…From the RV Meteor 44 , we used standard dship meteorological data for the EUREC 4 A Meteor cruise M161 (retrieved from http://dship.bsh.de/ , last accessed: 28 June 2022), surface heat fluxes (10.25326/312), ceilometer measurements ( https://doi.org/10.25326/53 ) and cloud radar data (v1.1, 10.25326/164). We further used data from AutoNaut Caravela 52 (10.25326/366) and 10-min air–sea flux data (v1.3, 10.25921/etxb-ht19) from the RV Ronald Brown 54 . Also, we used CLS Daily High Resolution Sea Surface Temperature maps (retrievable through the AERIS operational centre https://observations.ipsl.fr/aeris/eurec4a-data/SATELLITES/CLS/SST/ , last accessed: 28 June 2022, or directly from https://datastore.cls.fr/catalogues/sea-surface-temperature-infra-red-high-resolution-daily ), GOES-16 ABI SSTs from the ABI_G16-STAR-L3C-v2.7 product (10.25921/rtf0-q898) and ERA5 (ref.…”

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confidence: 99%

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Strong cloud–circulation coupling explains weak trade cumulus feedback

Vogel

Albright

Vial

et al. 2022

Nature

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Shallow cumulus clouds in the trade-wind regions cool the planet by reflecting solar radiation. The response of trade cumulus clouds to climate change is a key uncertainty in climate projections1–4. Trade cumulus feedbacks in climate models are governed by changes in cloud fraction near cloud base5,6, with high-climate-sensitivity models suggesting a strong decrease in cloud-base cloudiness owing to increased lower-tropospheric mixing5–7. Here we show that new observations from the EUREC4A (Elucidating the role of cloud-circulation coupling in climate) field campaign8,9 refute this mixing-desiccation hypothesis. We find the dynamical increase of cloudiness through mixing to overwhelm the thermodynamic control through humidity. Because mesoscale motions and the entrainment rate contribute equally to variability in mixing but have opposing effects on humidity, mixing does not desiccate clouds. The magnitude, variability and coupling of mixing and cloudiness differ markedly among climate models and with the EUREC4A observations. Models with large trade cumulus feedbacks tend to exaggerate the dependence of cloudiness on relative humidity as opposed to mixing and also exaggerate variability in cloudiness. Our observational analyses render models with large positive feedbacks implausible and both support and explain at the process scale a weak trade cumulus feedback. Our findings thus refute an important line of evidence for a high climate sensitivity10,11.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Strong cloud–circulation coupling explains weak trade cumulus feedback

Vogel

Albright

Vial

et al. 2022

Nature

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“…Sea tests revealed that AutoNaut vessels often tilt due to the effects of waves, currents, and other marine conditions. AutoNaut vessels employ hydrofoil propulsion, similar to asymmetric trajectory propulsion 11,26 . Currently, research on utilizing asymmetric hydrofoil features to enhance propulsive performance is gaining momentum.…”

Section: Introductionmentioning

confidence: 99%

Propulsion Performance of the Full-Active Hydrofoil under Asymmetric Arc-Trajectory

Qi,

Xing,

Shang

et al. 2024

Preprint

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Unmanned vessels, essential for ocean observation, often utilize an active hydrofoil propulsion system. When a vessel moves in waves, the tilted swing arm causes the motion trajectory of the hydrofoil to be asymmetric. This study employs a turbulence model with a Reynolds number of 105, simulated using the finite volume method (FVM) and the Navier-Stokes equations. Numerical simulations are then used to analyze the effects of the swing arm amplitude, arm length, and asymmetry ratio on the propulsive performance of a full-active hydrofoil with an asymmetric arc-trajectory. This asymmetrical arc-trajectory has a significant impact on the propulsion performance of the hydrofoil, especially when the asymmetry ratio is large. When the asymmetry ratio is 0.66, the mean thrust coefficient of the hydrofoil decreases by 68.37%, compared to the symmetric case. We further point out that such decrease is achieved through changes in foil flapping velocities and foil-vortex interactions between unequal down-stroke and up-stroke phases. However, when the asymmetry ratio is small, the impact of the asymmetric arc-trajectory can be almost negligible. Additionally, we find that the propulsion performance of the hydrofoil increases with increasing swing arm amplitude and arm length. These findings not only provide insights toward the hydrodynamics characteristics of the hydrofoil in asymmetric arc-trajectory mode, but also offer a reference to the design of the high-performance flapping hydrofoil propulsion system.

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Wave devouring propulsion: An overview of flapping foil propulsion technology

Xing

Yang

2023

Renewable and Sustainable Energy Reviews

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First measurements of ocean and atmosphere in the Tropical North Atlantic using Caravela, a novel uncrewed surface vessel

Cited by 5 publications

References 11 publications

Strong cloud–circulation coupling explains weak trade cumulus feedback

Strong cloud–circulation coupling explains weak trade cumulus feedback

Propulsion Performance of the Full-Active Hydrofoil under Asymmetric Arc-Trajectory

Wave devouring propulsion: An overview of flapping foil propulsion technology

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