s s Wind-induced circulation The wind-induced circulation can compete with estuarine circulation, or act in concert The wind-induced circulation will depend on stratification: depth-dependent under stratified conditions weak depth-dependence under homogeneous conditions s Weak Depth-Averaged Transport s Large Depth-Mean Transport

sx Wind-Induced Surface Slope Can be assessed from the vertical integration of the linearized u momentum equation, with no rotation @ steady state: Note that a westward sx (negative) produces a negative slope. sx x1 x2 y x x1 x2  Wind will pile up water in the direction toward which it blows.

Wind-driven flow and bathymetric effects non-dimensionalized momentum balance: non-dimensional variables: subscript indicates dimensional variables boundary conditions Integrating twice and applying boundary conditions:

volume transport no net volume transport

Along the Estuary: Pressure Gradient + Friction Winant (2004) Along the Estuary: Pressure Gradient + Friction Across the Estuary: Pressure Gradient + Friction

X t ROMS (full dynamics) Homogeneous fluid with rotation Sanay & Valle-Levinson (2005) ROMS (full dynamics) Homogeneous fluid with rotation (red is downwind; blue is upwind)

Particle trajectories (high E) (low E) y x y z y x y z Particle trajectories Winant (2004)

t Examples of bathymetric effects on wind-induced flow Looking into lagoon Red = Water going out Blue = Water going in

Residual Flow at Bahía Concepción, Chile (looking seaward)

Matlab code Winant’s (2004) clear all close all [y,z]=meshgrid(-1:.05:1,-1:.05:0); h=1-abs(y); % bathymetry y1=y(1,:); h1=h(1,:); % first row of ‘y’ and ‘z’ dn=1.5*mean(h1.^2)/mean(h1.^3); % d eta/dx u=dn*(z.^2-h.^2)/2+z+h; % u matrix ll=[-4,-3,-1,-.25,-.2,0]; % contour intervals to plot an label colormap pink contourf(y,z,u,ll) hold on contour(y,z,u,'ShowText','on','LineWidth',1.,'LineColor',[0 0 0]) fill([-1,y1,1],[-1,-h1,-1],'w')