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  • Online Resource  (14)
  • Physics  (14)
  • UA 4548  (14)
  • 11
    Online Resource
    Online Resource
    An Investigation of the Stability Dependence of SST-Induced Vertical Mixing over the Ocean in the Operational Met Office Model
    American Meteorological Society ; 2017
    In:  Journal of Climate Vol. 30, No. 1 ( 2017-01), p. 91-107
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 30, No. 1 ( 2017-01), p. 91-107
    Abstract: This study presents an assessment of the impact of a March 2006 change in the Met Office operational global numerical weather prediction model through the introduction of a nonlocal momentum mixing scheme. From comparisons with satellite observations of surface wind speed and sea surface temperature (SST), it is concluded that the new parameterization had a relatively minor impact on SST-induced changes in sea surface wind speed in the Met Office model in the September and October 2007 monthly averages over the Agulhas Return Current region considered here. The performance of the new parameterization of vertical mixing was evaluated near the surface layer and further through comparisons with results obtained using a wide range of sensitivity of mixing parameterization to stability in the Weather Research and Forecasting (WRF) Model, which is easily adapted to such sensitivity studies. While the new parameterization of vertical mixing improves the Met Office model response to SST in highly unstable (convective) conditions, it is concluded that significantly enhanced vertical mixing in the neutral to moderately unstable conditions (nondimensional stability [Formula: see text] between 0 and −2) typically found over the ocean is required in order for the model surface wind response to SST to match the satellite observations. Likewise, the reduced mixing in stable conditions in the new parameterization is also relatively small; for the range of the gradient Richardson number typically found over the ocean, the mixing was reduced by a maximum of only 10%, which is too small by more than an order of magnitude to be consistent with the satellite observations.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-16-0086.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2017
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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    Online Resource
  • 12
    Online Resource
    Online Resource
    Observations of SST-Induced Perturbations of the Wind Stress Field over the Southern Ocean on Seasonal Timescales
    American Meteorological Society ; 2003
    In:  Journal of Climate Vol. 16, No. 14 ( 2003-07-15), p. 2340-2354
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 16, No. 14 ( 2003-07-15), p. 2340-2354
    Abstract: The surface wind stress response to sea surface temperature (SST) over the latitude range 30°–60°S in the Southern Ocean is described from the National Aeronautics and Space Administration's QuikSCAT scatterometer observations of wind stress and Reynolds analyses of SST during the 2-yr period August 1999 to July 2001. While ocean–atmosphere coupling at midlatitudes has previously been documented from several case studies, this is the first study to quantify this relation over the entire Southern Ocean. The spatial structures of the surface wind perturbations with wavelengths shorter than 10° latitude by 30° longitude are closely related to persistent spatial variations of the SST field on the same scales. The wind stress curl and divergence are shown to be linearly related, respectively, to the crosswind and downwind components of the SST gradient. The curl response has a magnitude only about half that of the divergence response. This observed coupling is consistent with the hypothesis that SST modification of marine atmospheric boundary layer (MABL) stability affects vertical turbulent mixing of momentum, inducing perturbations in the surface winds. The nonequivalence between the responses of the curl and divergence to the crosswind and downwind SST gradients suggests that secondary circulations in the MABL may also play an important role by producing significant perturbations in the surface wind field near SST fronts that are distinct from the vertical turbulent transfer of momentum. The importance of the wind stress curl in driving Ekman vertical velocity in the open ocean implies that the coupling between winds and SST may have important feedback effects on upper ocean processes near SST fronts.
    Type of Medium: Online Resource
    ISSN: 1520-0442 , 0894-8755
    URL: Article
    DOI: 10.1175/2780.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2003
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 13
    Online Resource
    Online Resource
    The Dynamics of the ENSO–Atlantic Hurricane Teleconnection: ENSO-Related Changes to the North African–Asian Jet Affect Atlantic Basin Tropical Cyclogenesis
    American Meteorological Society ; 2009
    In:  Journal of Climate Vol. 22, No. 9 ( 2009-05-01), p. 2458-2482
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 22, No. 9 ( 2009-05-01), p. 2458-2482
    Abstract: The nature of the teleconnection linking ENSO variability with Atlantic basin tropical storm formation is investigated. Solutions of the linearized barotropic vorticity equation forced with August–October El Niño event divergence produce upper-tropospheric vorticity anomalies over the Sahel and at the mouth of the North African–Asian (NAA) jet over the tropical Atlantic. These responses are similar in magnitude and orientation to observed ENSO vorticity variability for this region. Further investigation reveals that the vorticity anomalies over the subtropical Atlantic develop primarily in response to very low wavenumber, westward-propagating stationary Rossby waves excited by El Niño–related convective activity over the equatorial Pacific Ocean. However, the dynamics of this teleconnection change as the Atlantic basin hurricane season progresses. In August and September the response is dominated by the westward-propagating stationary Rossby waves that alter vorticity within the NAA jet and to its south. The upper-tropospheric nondivergent zonal wind anomalies produced by these vorticity anomalies are similar in pattern to observed zonal wind and vertical zonal wind shear anomalies, which suppress Atlantic basin tropical cyclogenesis. By October, eastward-propagating signals also develop over the tropical Atlantic Ocean in response to El Niño conditions. Over the main development region of Atlantic basin tropical cyclogenesis, these eastward-propagating Rossby waves appear to destructively interfere with the vorticity changes produced by the westward-propagating Rossby waves within the NAA jet. In addition, the NAA jet has shifted south by October. Consequently, the resultant upper-tropospheric nondivergent zonal wind perturbations for October are weak and suggest that ENSO should have little effect on rates of Atlantic basin tropical cyclogenesis during October. Statistical analyses of monthly ENSO-related changes in Atlantic basin tropical storm formation support this hypothesis.
    Type of Medium: Online Resource
    ISSN: 1520-0442 , 0894-8755
    URL: Article
    DOI: 10.1175/2008JCLI2360.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2009
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 14
    Online Resource
    Online Resource
    The Amplification of East Pacific Madden–Julian Oscillation Convection and Wind Anomalies during June–November
    American Meteorological Society ; 2003
    In:  Journal of Climate Vol. 16, No. 21 ( 2003-11), p. 3482-3497
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 16, No. 21 ( 2003-11), p. 3482-3497
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/1520-0442(2003)016〈3482:TAOEPM〉2.0.CO;2
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2003
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
    Location Call Number Limitation Availability
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