[MITgcm-support] Spinup in a 2-D channel surface waves?

[Jody Klymak]

Hello,

I want to perform spinup of a 2-D channel to along-channel winds for  
a class I'm teaching.  While I'm sure the MITgcm is overkill for  
this, I'm at least vaguely familiar with it.

I have the winds blowing, the channel seems to behave, and an Ekman  
layer seems to form.  However, the surface pressure is not behaving  
and I'm finding the docs on the surface pressure solver opaque enough  
that I thought I'd ask for help here.

My vertical resolution near the surface is 0.75m, for 40 bins.  The  
total water depth is as deep as 200 m, with sloping sides in a 20 km- 
wide channel.  dx = 200 m.

What happens is I blow a south wind, the Ekman layers pile water up  
in the west and move it away from the East. However, the depth  
anomalies do not seem to get large enough, and the ones that do form
do not propagate more than a couple of grid cells away at anything  
like the surface wave speed.  For instance, the cross-channel Ekman  
flux reaches 1 m^2/s, which should be changing the surface tilt by  
something like 36 cm over an hour. However, after 7 h or so (in sim  
time), I still have 10 cm-high anomalies in the grids adjacent to the  
edge of the channel, and nothing more than 3 grid cells away.

Any hints what I've done wrong or suggestions for getting the  
barotropic pressure gradient to set up properly across the channel  
would be very helpful!

Thanks a lot,  Jody

In "data" I hope the relevant parameters are:

viscAz=1.E-3,
viscAh=1.E-3,
no_slip_sides=.FALSE.,
no_slip_bottom=.TRUE.,
viscA4=0.E12,

gBaro=9.81,
rigidLid=.FALSE.,
implicitFreeSurface=.TRUE.,

nonHydrostatic=.FALSE.,
hFacMin=0.5,
implicSurfPress=0.5,
implicDiv2DFlow=0.5,
nonlinFreeSurf=3,
hFacInf=0.1,
hFacSup=2.0,
exactConserv=.TRUE.,




--
Jody Klymak
http://web.uvic.ca/~jklymak/