Effects of mesoscale sea-surface temperature fronts on the marine atmospheric boundary layer

Skyllingstad, Eric D.; Vickers, Dean; Mahrt, L.; Samelson, R. M.

doi:10.1007/s10546-006-9127-8

Cited by 69 publications

(100 citation statements)

References 22 publications

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“…This enhanced downward turbulent mixing results in stronger surface winds over warm water. Support for the vertical mixing of momentum idea is found in the near-equatorial model of de Szoeke and Bretherton (2004) and the midlatitude large eddy simulations of Skyllingstad et al (2006). Samelson et al (2006) suggest that the stress at the sea surface must depend on the planetary boundary layer thickness so that the surface winds must be positively correlated with boundary layer thickness and, thus, sea surface temperature.…”

Section: Introductionmentioning

confidence: 82%

Midlatitude Wind Stress–Sea Surface Temperature Coupling in the Vicinity of Oceanic Fronts

2007

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The influences of strong gradients in sea surface temperature on near-surface cross-front winds are explored in a series of idealized numerical modeling experiments. The atmospheric model is the Naval Research Laboratory Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) model, which is fully coupled to the Regional Ocean Modeling System (ROMS) ocean model. A series of idealized, two-dimensional model calculations is carried out in which the wind blows from the warm-to-cold side or the cold-to-warm side of an initially prescribed ocean front. The evolution of the near-surface winds, boundary layer, and thermal structure is described, and the balances in the momentum equation are diagnosed. The changes in surface winds across the front are consistent with previous models and observations, showing a strong positive correlation with the sea surface temperature and boundary layer thickness. The coupling arises mainly as a result of changes in the flux Richardson number across the front, and the strength of the coupling coefficient grows quadratically with the strength of the cross-front geostrophic wind. The acceleration of the winds over warm water results primarily from the rapid change in turbulent mixing and the resulting unbalanced Coriolis force in the vicinity of the front. Much of the loss/gain of momentum perpendicular to the front in the upper and lower boundary layer results from acceleration/ deceleration of the flow parallel to the front via the Coriolis term. This mechanism is different from the previously suggested processes of downward mixing of momentum and adjustment to the horizontal pressure gradient, and is active for flows off the equator with sufficiently strong winds. Although the main focus of this work is on the midlatitude, strong wind regime, calculations at low latitudes and with weak winds show that the pressure gradient and turbulent mixing terms dominate the cross-front momentum budget, consistent with previous work.

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Section: Introductionmentioning

confidence: 82%

Midlatitude Wind Stress–Sea Surface Temperature Coupling in the Vicinity of Oceanic Fronts

2007

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“…Processes that are resolution dependent may also explain this increase in a negative correlation. Recent studies (Minobe et al 2008;Skyllingstad et al 2007) show that sharp SST fronts typical of western boundary regions tend to destabilize the Marine Atmospheric Boundary Layer, resulting in atmospheric dynamics that are directly driven by the underlying ocean. In our model, the sharpening of SST gradients along the western boundary resulting from the increased oceanic resolution might induce a stronger atmospheric response, explaining the increased correlation T ′ Q ′ at higher resolution.…”

Section: Air-sea Heat Fluxesmentioning

confidence: 99%

Oceanic control of multidecadal variability in an idealized coupled GCM

et al. 2015

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International audienceIdealized ocean models are known to develop intrinsic multidecadal oscillations of the meridional overturning circulation (MOC). Here we explore the role of ocean–atmosphere interactions on this low-frequency variability. We use a coupled ocean–atmosphere model set up in a flat-bottom aquaplanet geometry with two meridional boundaries. The model is run at three different horizontal resolutions (4°, 2° and 1°) in both the ocean and atmosphere. At all resolutions, the MOC exhibits spontaneous variability on multidecadal timescales in the range 30–40 years, associated with the propagation of large-scale baroclinic Rossby waves across the Atlantic-like basin. The unstable region of growth of these waves through the long wave limit of baroclinic instability shifts from the eastern boundary at coarse resolution to the western boundary at higher resolution. Increasing the horizontal resolution enhances both intrinsic atmospheric variability and ocean–atmosphere interactions. In particular, the simulated atmospheric annular mode becomes significantly correlated to the MOC variability at 1° resolution. An ocean-only simulation conducted for this specific case underscores the disruptive but not essential influence of air–sea interactions on the low-frequency variability. This study demonstrates that an atmospheric annular mode leading MOC changes by about 2 years (as found at 1° resolution) does not imply that the low-frequency variability originates from air–sea interactions

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“…Conventional diagnostics have been performed by using the momentum equation at a given height (Wai and Stage 1989;Small et al 2003;Song et al 2006;Skyllingstad et al 2007;Spall 2007), as given by…”

Section: Introductionmentioning

confidence: 99%

Diagnostics for Near-Surface Wind Response to the Gulf Stream in a Regional Atmospheric Model*

et al. 2014

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The mechanisms acting on near-surface winds over the Gulf Stream are diagnosed using 5-yr outputs of a regional atmospheric model. The diagnostics for the surface-layer momentum vector, its curl, and its convergence are developed with a clear separation of pressure adjustment from downward momentum inputs from aloft in the surface-layer system. The results suggest that the downward momentum mixing mechanism plays a dominant role in contributing to the annual-mean climatological momentum curl, whereas the pressure adjustment mechanism plays a minor role. In contrast, the wind convergence is mainly due to the pressure adjustment mechanism. This can be explained by the orientation of background wind to the sea surface temperature front. The diagnostics also explain the relatively strong seasonal variation in surfacelayer momentum convergence and the small seasonal variation in curl. Finally, the surface-layer response to other western boundary currents is examined using a reanalysis dataset.

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Effects of mesoscale sea-surface temperature fronts on the marine atmospheric boundary layer

Cited by 69 publications

References 22 publications

Midlatitude Wind Stress–Sea Surface Temperature Coupling in the Vicinity of Oceanic Fronts

Midlatitude Wind Stress–Sea Surface Temperature Coupling in the Vicinity of Oceanic Fronts

Oceanic control of multidecadal variability in an idealized coupled GCM

Diagnostics for Near-Surface Wind Response to the Gulf Stream in a Regional Atmospheric Model*

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