[MITgcm-support] exf interp

[Matthew Mazloff]

Hi Chris,

Would it be easier for you to send me your code....how involved is  
it?  What are your plans?
The reason I ask is that this is for my California setup, but I would  
like to check this in my Southern Ocean set-up too.  Also I plan on  
increasing the duration of my California set-up soon and would hate to  
have to keep bugging you to please fix my fields.

Thanks
-Matt


On Oct 21, 2009, at 11:13 AM, Chris Hill wrote:

> Hi matt
>
> can you put your wind fields, grid etc... Somewhere @ MIT. I have code
> to fix this offline, but have never found a real setup where it
> mattered!
>
> Chris
>
> On Wednesday, October 21, 2009, Matthew Mazloff <mmazloff at mit.edu>  
> wrote:
>> Hello,
>>
>> Sorry, I do not have good news.  I ran the model and the time-mean  
>> gradient of both wind stress (e.g. EXFtaux) and wind speed (e.g.  
>> EXFuwind) reveal the original NCEP grid.  Basically the plot of the  
>> curl of wind velocity looks the same as the plot I sent you  
>> previously of wind-stress curl.  lThe problem appears not to be the  
>> bilinear interpolation of the buoyancy forcing terms; it appears  
>> that the bicubic interpolation of the wind velocity is not smooth  
>> enough to yield a smooth gradient.
>>
>> Any ideas?
>>
>> -Matt
>>
>> ps> this calculation was done on an optimized solution -- I still  
>> need to verify to make sure this feature has not been introduced by  
>> controls -- but I am doubtful that the ctrl fields are the cause as  
>> these are smoothed with Gael's package (100km length scale) and the  
>> jump at the half-degrees are quite sharp
>>
>>
>>
>>
>> On Oct 17, 2009, at 2:53 PM, Dimitris Menemenlis wrote:
>>
>>
>> The issue was mainly one of negative rain
>> (and perhaps also negative downward radiations and humidity).
>> These will probably not be a problem in your limited domain.
>>
>> When you run your test on Monday, could you also save the wind  
>> velocity fields:
>>
>> 179 |EXFuwind|  1 |SM      U1      |m/s             |zonal 10-m  
>> wind speed, >0 increases uVel
>> 180 |EXFvwind|  1 |SM      U1      |m/s             |meridional 10- 
>> m wind speed, >0 increases uVel
>> 181 |EXFwspee|  1 |SM      U1      |m/s             |10-m wind  
>> speed modulus ( >= 0 )
>>
>> to see if there are any discontinuities are in the curl of the wind  
>> velocity.
>> If Chris' hypothesis is correct you will not see a rectangular  
>> pattern in
>> the curl of the wind.  if you do, then we will need to use Chris'
>> interpolation scheme.
>>
>> D.
>>
>> On Oct 17, 2009, at 1:38 PM, Matthew Mazloff wrote:
>>
>>
>> Hi Chris,
>>
>> Yeah, its relatively easy to test.  I'll give it a try on monday and
>> let you know
>>
>> -Matt
>>
>> Dimitris, what issues arose when using bicubic before for buoyancy
>> terms -- anything specific I should look out for?
>>
>> -Matt
>>
>>
>> On Oct 17, 2009, at 1:14 PM, Chris Hill wrote:
>>
>>
>> Matt,
>>
>> I think the bicubic is worth trying. As I understand Benny's code it
>> is meant to be c1 continuous
>> which should help.
>> My hope is that the bilinear temps are affecting the wind stress
>> (because atemp/SST feature in static stability calcs in bulk formula
>> and in turbulent mixing calcs and so affect momentum flux).
>> Is it quick(ish) to run a test?
>>
>> If this doesn't work I have a couple of other things that would be
>> kind of interesting to try. They involve doing stuff offline
>> initially.
>>
>> Chris
>>
>> On Sat, Oct 17, 2009 at 1:36 PM, Matthew Mazloff <mmazloff at mit.edu>
>> wrote:
>>
>> Hi Chris,
>>
>>
>> Are the surface data sets 1/2 degree res?
>>
>>
>> 1 degree res -- starting at the half degree:
>> uwind_lon0         = 229.5D0,
>> uwind_lon_inc      = 1.D0,
>> uwind_lat0         = 26.5D0,
>> uwind_lat_inc      = 15*1.D0,
>>
>>
>> My guess is it is the piecewise constant in the aTemp/aQ/radiation?
>>
>>
>> I'm confused, I'm plotting windstress curl, and the wind speed uses
>> bicubic
>> interpolation already.
>> Do you think this is a feedback from buoyancy forcing be linearly
>> interploated?  I can check the wind speed to ensure the signal is
>> not coming
>> from the (ocean) relative speed in the stress calculation.
>>
>>
>> If the spline is done right
>> the overshoots should be small in a limited area domain, so you
>> could try
>> that.
>>
>>
>> You mean trying bicubic for buoyancy components?
>>
>>
>> Thanks for the help!
>> -Matt
>>
>>
>>
>>
>>
>> Chris
>>
>> On Sat, Oct 17, 2009 at 11:38 AM, Matthew Mazloff <mmazloff at mit.edu>
>> wrote:
>>
>>
>> Hi Dimitris,
>>
>> See the lines at X.5 degrees.  Its not very noticeable in
>> snapshots, but
>> really stands out in the mean as the signal is accumulated
>>
>> -Matt
>>
>>
>>
>>
>>
>>
>> On Oct 17, 2009, at 7:42 AM, Dimitris Menemenlis wrote:
>>
>>
>> Matt, could you send an example figure of problem?
>>
>> On Oct 17, 2009, at 7:29 AM, Matthew Mazloff wrote:
>>
>>
>> Hi Dimitris,
>>
>> Ah yes, I see this now.  Very nice.  Unfortunately the gridding
>> is
>> still noticeable in my plots of wind speed gradient.  I am able
>> to
>> pick out the exact locals where the forcing is prescribed --
>> meaning
>> the interpolation is not smooth.  This is not good for plotting
>> wind-
>> stress curl. Have you noticed this on your high-res set-ups?
>> Do you
>> think this is a problem?  Should we (can we) try a smoother
>> interp
>> method?
>>
>> -
>
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