Initial Time Dependence of Wind- and Density-driven Lagrangian Residual
Velocity in a Tide-dominated Bay
Abstract
The nonlinear effect of the summer SE wind and density on the 3D
structures of the full Lagrangian residual velocity (LRV) was quantified
for a general nonlinear system, using Jiaozhou Bay, China (JZB), as the
test site. In the tidally energetic JZB, the basic patterns of the wind-
and density-driven full LRV were found to be consistent with simplified
semi-analytical solutions but highly dependent on the initial times. The
wind-driven full LRVs detected at different tidal phases showed similar
laterally sheared, three-layer circulation, but the main branches could
migrate across nearly half of the inner bay. The density-driven,
clockwise flow dominated the western inner bay at low tide, while almost
disappearing at high tide. The effect of density generally enhanced
outward flow in the surface layer and inward flow in the bottom layer.
Along-trajectory, integrated momentum balances indicated that viscosity
was the main force responsible for the time-dependence of the
wind-driven full LRV, while viscosity and the barotropic and baroclinic
pressure gradients were the main drivers of the intra-tidal variations
in the density-driven full LRV. Generally, the summer wind and density
had opposing effects, although their influence was weaker than that of
the tide and could not change the patterns of the tide-driven full LRV.
The results indicated that when the effects of wind and density on the
coastal circulation of tidally energetic waters are analysed, both the
3D structures and the possibility of a high initial tidal phase
dependency should be considered.