[MITgcm-support] filters for vertical velocity in cubed-sphere grid

[Andrea Molod]

hi yuan,

its up to you if you want to wait. but i know that if you
use the 'newer' grid files this problem will get much better.

good luck,
andrea

On Wed, 11 
Jul 
2007, Yuan Lian wrote:

> Hi Andrea,
>
> Thanks for your help. I tried several parameter configurations in "data" and 
> it seems working a
> little better now at grids corners. I have contacted with Jean-Michel but he 
> hasn't come back yet.
> I may be visiting MIT by the end of July and we can discuss the problem in 
> details by then.
>
> Cheers,
> Yuan
>
> Andrea Molod wrote:
>> hi yuan,
>> 
>>> I noticed Shapiro filter is not applied to vertical velocity (atmospheric 
>>> model, maybe generally for oceanic model as well).
>>> Ideally, the vertical velocity should be calculated from continuity 
>>> equation. However, corner effect on vertical velocity are
>>> noticeable, ie, stronger upward or downward motions comparing to 
>>> elsewhere. In a neutrally stable atmosphere, air at corners
>>> will experience adiabatic heating or cooling and cause local maximum (or 
>>> minimum) of temperature.
>> 
>> can you tell me which setup/experiment etc... you are using? i ask
>> because there are a set of grid files for the 32x32 cube that were put
>> together by jean-michel to address this issue. indeed, the vertical
>> velocity at the corners under certain circumstances got noisy, and
>> he made some adjustments to the locations of the grid cell edges
>> relative to the centers (if i have this correct...) that made most
>> of this go away. you can find them in the directory: 
>> verification/fizhi-cs-32x32x40/input and they are called dxC1....
>> 
>> as far as i understand things, trying to put the vertical velocity
>> through the shapiro filter would not 'really' address the problem,
>> it would sort of mask it and maybe even make a bigger mess.
>> 
>>> 
>>> Also, it there any way to generate high resolution cubed-sphere grid while 
>>> maintaining the ratio of grid areas?
>>> 
>> 
>> again, as dimitris asked, what do you mean by 'high res'?
>> (the link he gave you is for the 'really' high res - i have generated
>> a new cubed sphere grid FROM the one he talked about with just under 1 
>> degree resolution). also - as far as i know, any of the cubed sphere
>> grids that people here have generated try to maintain the good ratio of 
>> grid areas.....
>> 
>> hope some of this answers your questions.
>> 
>> andrea
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>> MITgcm-support at mitgcm.org
>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>> 
>
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-- 
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Andrea M. Molod, PhD.
Department of Earth, Atmospheric & Planetary Sciences
MIT
Tel: (617) 253-5458, Email: amolod at mit.edu
WWW:http://paoc.mit.edu/paoc/people/person.asp?position=Postdoc&who=molod
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