1. Wind-Driven Circulation in a Shelf Valley. Part II: Dynamics of the Along-Valley Velocity and Transport.
- Author
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Zhang, Weifeng (Gordon) and Lentz, Steven J.
- Subjects
ATMOSPHERIC circulation ,THEORY of wave motion ,BATHYMETRY ,ROSSBY number ,COMPUTER simulation - Abstract
The dynamics controlling the along-valley (cross-shelf) flow in idealized shallow shelf valleys with small to moderate Burger Number are investigated, and analytical scales of the along-valley flows are derived. This paper follows Part 1 which shows that along-shelf winds in the opposite direction to coastal-trapped wave propagation (upwelling regime) force a strong up-valley flow caused by the formation of a lee wave. In contrast, along-shelf winds in the other direction (downwelling regime) do not generate a lee wave and consequently force a relatively weak net down-valley flow. The valley flows in both regimes are cyclostrophic with order-one Rossby number. A major difference between the two regimes is the along-shelf length scales of the alongvalley flows, L
x . In the upwelling regime Lx depends on the valley width, Wc , and the wavelength (iw) of the coastal-trapped lee wave arrested by the along-shelf flow, Us . In the downwelling regime Lx depends on the inertial length scale, \Us \lf, and Wc . The alongvalley velocity scale in the upwelling regime, given by VN ≈ √ π Hc /H3 fWc λlw /2πLx (1+L2 x /L2 c )-1 e- (πWMc )(λlw ), is based on potential vorticity (PV) conservation and lee-wave dynamics (Hs and Hc are the shelf and valley depth scales, respectively, and fis Coriolis). The velocity scale in the downwelling regime, given by |Vc |≈(Hc |Hs )[1+L2 x |L2 c ]-1 fLx is based on PV conservation. The velocity scales are validated by the numerical sensitivity simulations and can be Useful for observational studies of along-valley transports. The work provides a framework for investigating cross-shelf transport induced by irregular shelf bathymetry and calls for future studies of this type under realistic environmental conditions and over a broader parameter space. [ABSTRACT FROM AUTHOR]- Published
- 2018
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