[MITgcm-support] exf interp

Sat Oct 17 17:53:49 EDT 2009

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?
>>>>>>>
>>>>>>> -Matt
>>>>>>>
>>>>>>> On Oct 16, 2009, at 5:03 PM, Dimitris Menemenlis wrote:
>>>>>>>
>>>>>>>> Matt, I hardcoded bilinear interpolation for tracer fields
>>>>>>>> because
>>>>>>>> overshoots can be problematic and bicubic for wind velocity  
>>>>>>>> (see
>>>>>>>> exf_set_uv.F) for stress fields because the second derivative
>>>>>>>> matters.  I would recommend to leave as is.  Other
>>>>>>>> combinations can
>>>>>>>> (or did) cause trouble.  Dimitris
>>>>>>>>
>>>>>>>> On Oct 16, 2009, at 3:21 PM, Matthew Mazloff wrote:
>>>>>>>>
>>>>>>>>> Hello,
>>>>>>>>>
>>>>>>>>> It appears the model is equipped to do both bilinear and
>>>>>>>>> bicubic
>>>>>>>>> interpolation for exf_interp.F.  Interp_method, however, is
>>>>>>>>> hardcoded
>>>>>>>>> to bilinear interpolation.  This does matter for my 1/16
>>>>>>>>> degree set-
>>>>>>>>> up.  Can anyone confirm that the bicubic interpolation is ok
>>>>>>>>> -- and I
>>>>>>>>> can go ahead and use this option.
>>>>>>>>>
>>>>>>>>> -Thanks,
>>>>>>>>> Matt
>>>>>>
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