登录
 机构网站
  1. 首页
  2. 情报产品
  3. 快讯详情

《Satellite Observations of Mesoscale Eddy-Induced Ekman Pumping》

  • 来源专题：物理海洋学知识资源中心
  • 编译者： cancan
  • 发布时间：2018-11-14

  • Gaube P, Chelton D B, Samelson R M, et al. Satellite Observations of Mesoscale Eddy-Induced Ekman Pumping.

    来源： Journal of Physical Oceanography, 2015, 45(1):104-132.

    摘要: Three mechanisms for self-induced Ekman pumping in the interiors of mesoscale ocean eddies are in-vestigated. The first arises from the surface stress that occurs because of differences between surface wind and ocean velocities, resulting in Ekman upwelling and downwelling in the cores of anticyclones and cyclones, respectively. The second mechanism arises from the interaction of the surface stress with the surface current vorticity gradient, resulting in dipoles of Ekman upwelling and downwelling. The third mechanism arises from eddy-induced spatial variability of sea surface temperature (SST), which generates a curl of the stress and therefore Ekman pumping in regions of crosswind SST gradients. The spatial structures and relative mag-nitudes of the three contributions to eddy-induced Ekman pumping are investigated by collocating satellite-based measurements of SST, geostrophic velocity, and surface winds to the interiors of eddies identified from their sea surface height signatures. On average, eddy-induced Ekman pumping velocities approach O(10) cm day 21 . SST-induced Ekman pumping is usually secondary to the two current-induced mechanisms for Ekman pumping. Notable exceptions are the midlatitude extensions of western boundary currents and the Antarctic Circumpolar Current, where SST gradients are strong and all three mechanisms for eddy-induced Ekman pumping are comparable in magnitude. Because the polarity of current-induced curl of the surface stress opposes that of the eddy, the associated Ekman pumping attenuates the eddies. The decay time scale of this attenuation is proportional to the vertical scale of the eddy and inversely proportional to the wind speed. For typical values of these parameters, the decay time scale is about 1.3 yr。

    全文网址：http://ir.library.oregonstate.edu/xmlui/bitstream/1957/55177/1/GaubePeterCEOASSatelliteObservationsMesoscale.pdf

137浏览量
原文链接
相关报告

  • 《Global observations of nonlinear mesoscale eddies》
    • 来源专题：物理海洋学知识资源中心
    • 编译者：cancan
    • 发布时间：2018-11-14
    • Chelton, Dudley B.; Schlax, Michael G.; Samelson, Roger M.Global observations of nonlinear mesoscale eddies. 来源: Progress in Oceanography, 2011, 91(2):167-216 摘要: Sixteen years of sea-surface height (SSH) fields constructed by merging the measurements from two simultaneously operating altimeters are analyzed to investigate mesoscale variability in the global ocean. The prevalence of coherent mesoscale features (referred to here as “eddies”) with radius scales of O(100 km) is readily apparent in these high-resolution SSH fields. An automated procedure for identifying and tracking mesoscale features based on their SSH signatures yields 35,891 eddies with lifetimes ?16 weeks. These long-lived eddies, comprising approximately 1.15 million individual eddy observations, have an average lifetime of 32 weeks and an average propagation distance of 550 km. Their mean amplitude and a speed-based radius scale as defined by the automated procedure are 8 cm and 90 km, respectively. 全文网址：https://www.sciencedirect.com/science/article/pii/S0079661111000036
    166浏览量
    原文链接

  • 《Mesoscale to Submesoscale Transition in the California Current System. Part I: Flow Structure, Eddy Flux, and Observational Tests》
    • 来源专题：物理海洋学知识资源中心
    • 编译者：cancan
    • 发布时间：2018-11-14
    • Capet X, Mcwilliams J C, Molemaker M J, et al. Mesoscale to Submesoscale Transition in the California Current System. Part I: Flow Structure, Eddy Flux, and Observational Tests. 来源: Journal of Physical Oceanography, 2008, 38(38):44 摘要:In computational simulations of an idealized subtropical eastern boundary upwelling current system, similar to the California Current, a submesoscale transition occurs in the eddy variability as the horizontal grid scale is reduced to O(1) km. This first paper (in a series of three) describes the transition in terms of the emergent flow structure and the associated time-averaged eddy fluxes. In addition to the mesoscale eddies that arise from a primary instability of the alongshore, wind-driven currents, significant energy is transferred into submesoscale fronts and vortices in the upper ocean. The submesoscale arises through surface frontogenesis growing off upwelled cold filaments that are pulled offshore and strained in between the mesoscale eddy centers. In turn, some submesoscale fronts become unstable and develop submesoscale meanders and fragment into roll-up vortices. Associated with this phenomenon are a large vertical vorticity and Rossby number, a large vertical velocity, relatively flat horizontal spectra (contrary to the prevailing view of mesoscale dynamics), a large vertical buoyancy flux acting to restratify the upper ocean, a submesoscale energy conversion from potential to kinetic, a significant spatial and temporal intermittency in the upper ocean, and material exchanges between the surface boundary layer and pycnocline. Comparison with available observations indicates that submesoscale fronts and instabilities occur widely in the upper ocean, with characteristics similar to the simulations. 全文网址：http://www.myroms.org/Papers/Capet_2008a_JPO.pdf
    143浏览量
    原文链接