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  • Dynamic soaring  (2)
  • Antarctic Intermediate Water  (1)
  • 1
    facet.materialart.
    Unknown
    The mid-depth circulation of the northwestern tropical Atlantic observed by floats (2009)
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009): 1615-1632, doi:10.1016/j.dsr.2009.06.002.
    Description: A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600–1050 dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200–2050 dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e. g. shipborne or mooring observations. Mean transports in each of five zonal equatorial current bands is found to be between 2.7 and 4.5 Sv. Pathways carrying AAIW northward beyond the North Brazil Undercurrent are clearly visible in the mean velocity field, in particular a northward transport of 3.7 Sv across 16° N between the Antilles islands and the Mid- Atlantic Ridge. New maps of Lagrangian eddy kinetic energy and integral time scales are presented to quantify mesoscale activity. For the uNADW, mean flow and mesoscale properties are discussed as data availability allows. Trajectories in the uNADWeast of the Lesser Antilles reveal interactions between the Deep Western Boundary Current (DWBC) and the basin interior, which can explain recent hydrographic observations of changes in composition of DWBC water along its southward flow.
    Description: MOVE was funded by the Bundesministerium fu¨r Bildung und Forschung (grants 03F0246A and 03F0377B) as well as by the Deutsche Forschungsgemeinschaft (grant SE815/21), NBC by the National Science Foundation through grants OCE 97-29765 and OCE 01-36477, and SAMBA was fully supported by Ifremer.
    Keywords: Floats ; Tropical Atlantic ; Antarctic Intermediate Water ; North Atlantic Deep Wat ; Equatorial currents
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 2
    facet.materialart.
    Unknown
    Leonardo da Vinci’s discovery of the dynamic soaring by birds in wind shear (2018)
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Notes and Records: the Royal Society Journal of the History of Science (2018), doi:10.1098/rsnr.2018.0024.
    Description: Although Leonardo da Vinci (1452-1519) is well-known to have studied bird flight, few people realize that he was the first to document flight maneuvers now called dynamic soaring. Birds use these maneuvers to extract energy from the gradient of wind velocity (wind shear) for sustained flight. In his Manuscript E (circa 1513-1515) Leonardo described land birds performing flight maneuvers that match those of albatrosses and other seabirds when they are engaged in dynamic soaring over the ocean. His description predates by almost 400 years the first generally-accepted explanation of the physics of this soaring technique by Lord Rayleigh in 1883. Leonardo’s early description of dynamic soaring is one of his major aerodynamic discoveries.
    Keywords: Leonardo da Vinci ; Bird flight ; Bird soaring ; Soaring ; Dynamic soaring ; Wind shear
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 3
    facet.materialart.
    Unknown
    Upwind dynamic soaring of albatrosses and UAVs (2016)
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    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Progress in Oceanography 130 (2015): 146-156, doi:10.1016/j.pocean.2014.11.002.
    Description: Albatrosses have been observed to soar in an upwind direction using what is called here an upwind mode of dynamic soaring. The upwind mode is modeled using the dynamics of a two-layer Rayleigh cycle in which the lower layer has zero velocity and the upper layer has a uniform wind speed of W. The upwind mode consists of a climb across the wind-shear layer headed upwind, a 90° turn and descent across the wind- shear layer perpendicular to the wind, followed by a 90° turn into the wind. The increase of airspeed gained from crossing the wind-shear layer headed upwind is balanced by the decrease of airspeed caused by drag. Results show that a wandering albatross can soar over the ocean in an upwind direction at a mean speed of 8.4 m/s in a 3.6 m/s wind, which is the minimum wind speed necessary for sustained dynamic soaring. The main result is that an albatross can soar upwind much faster that the wind speed. The upwind dynamic soaring mode of a possible robotic albatross UAV (Unmanned Aerial Vehicle) is also modeled using a Rayleigh cycle. Maximum possible airspeeds are approximately equal to 9.5 times the wind speed of the upper layer. In a wind of 10 m/s, the maximum possible upwind (56 m/s) and across-wind (61 m/s) components of UAV velocity over the ocean result in a diagonal upwind velocity of 83 m/s. In sufficient wind, a UAV could, in principle, use fast diagonal speeds to rapidly survey large areas of the ocean surface and the marine boundary layer. Limitations to achieving such fast travel velocity are discussed and suggestions are made for further studies.
    Description: Financial support was provided by the F. Livermore Trust and Woods Hole Oceanographic Institution emeritus funds.
    Keywords: Dynamic soaring ; Energy-neutral soaring ; Albatross ; Robotic albatross ; Unmanned Aerial Vehicle ; UAV
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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