[MITgcm-support] linear growth of runoff

[Patrick Heimbach]

Dmitri,

sorry, can't really help you much,
have been away, and will again be soon.

But:
It seems that everything is working fine:
You tried constant-in-time runoff, and got linearly growing sea-level.
I reckon you are using real freshwater flux,
i.e. E-P-R gets added to surface elevation.
So, if your E-P-R field is out of balance, i.e. if it does not
add up to zero when integrated over the domain,
then your sea-level will grow linearly.

And second, when your globally integrated E-P-R increases linearly
as a consequence of linear interpolation in time of two
consecutive entries (the second entry being bigger than the first),
you will get quadratic growth in sea-level over the interpolation  
period.

So all seems to work well.

If you don't want to use real freshwater flux, then set
   useRealFreshWaterFlux=.FALSE.,
in file "data".

-Patrick



On Mar 12, 2007, at 9:47 PM, Dmitri Leonov wrote:

> Hello Patrick,
>
> Please let me know what exactly it was that you found wrong in my  
> input files. I've tried setting the runoffperiod to zero as you  
> suggested but the runoff still seems to be growing linearly - so  
> the problem is not in the time-interpolation but somewhere else.  
> This is not architecture or compiler specific as I originally  
> thought it might be: just got same results on a linux pc using g77.
>
> Maybe I'm not allowed to have closed boundaries when I have a non- 
> zero E-P-R, so it's not a good test? What do you mean by balancing  
> E-P-R fields? In the actual experiment I have an open boundary.
>
> If there is in fact some kind of bug there I thought some people  
> other than myself might be interested in looking into it. Otherwise  
> I'll need to find out what exactly was wrong with my set-up.
>
> Regards,
> Dmitri.
>
>
>> No, you got that wrong.
>> Time interpolation of runoff is working properly,
>> assuming you've set values in data.exf correctly.
>>
>>> 2) it gets interpolation period wrong so the slope depends on the  
>>> timestep (as if the period is specified in timesteps rather than  
>>> in seconds).
>>
>> Are your E-P-R fields balanced overall?
>>
>> -Patrick
>>
>>
>>> Jean-Michel Campin wrote:
>>>> Hi Dimitri,
>>>>
>>>> I forgot the important thing,
>>>> apparently, in your set-up, EXF produces a linear increase with  
>>>> time in run-off, but I don't know precisely what would need to  
>>>> be changed in data.exf & data.exf_clim to get a constant run- 
>>>> off. May be someone else will know.
>>>>
>>>> Jean-Michel
>>>>
>
> -- 
>
> ------------------------------------------------
> Dmitri A. Leonov
> Research Associate, Postdoctoral
> University of Washington, School of Oceanography
>
>
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---
Dr Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
MIT | EAPS, 54-1518 | 77 Massachusetts Ave | Cambridge, MA 02139, USA
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