Opened 14 years ago

Closed 13 years ago

#50 closed help (fixed)

Geostrophic winds STASH?

Reported by: caroline@… Owned by: um_support
Component: UM Model Keywords:
Cc: Platform:
UM Version:


Hello NCAS,

Is there a quick way of getting geostrophic winds out of the UM?


Change History (9)

comment:1 Changed 13 years ago by umdoc

Hello NCAS,

Just to go back to this and bump it up the queue. The easiest way to get geostrophic winds seems to be via NDdiag. However, this only outputs the winds on pressure surfaces, not height surfaces. I was wondering if there was not way to output on height surfaces?

Gerry here has suggested the simple way might be to create a separate modset to output a new diagnostic (ug/vg on zlevs), but has anyone already got one? I was surprised there was no geostropic wind STASH.

Many thanks,


comment:2 Changed 13 years ago by lois

Hello Caroline,
I don't really have a definitive answer to your problem. Having talked to various people what I found out was

  • NDDIAG is for converting from model levels to pressure levels so it is not the place to do what you want
  • the documentation for MDIAG and NDDIAG is missing so I will chase that up and make sure it is on the web site
  • 'it should be easy to get geostrophic winds from the model' ie you can write a modset to do it. There may well be people who have such a modset but I have not found anyone here who has one.


comment:3 Changed 13 years ago by umdoc

Thanks Lois,

I have not written a modset before and Gerry only has examples from the LEM, so ia there an example modset which outputs a new diagnostic that I could change? Or is there documentation/website/modset library out there already?

Many thanks,


comment:4 Changed 13 years ago by cwang

Hi Caroline & Lois,

The usual way to get a field on height level is to use jview where you can do 'vertical interpolation'.

If you have pressure level data which normally derived by running NDDIAG, then in jview you can use
'vertical interpolation' to interpolate pressure level data to height level.


comment:5 Changed 13 years ago by cbain

Hi Chang, Lois,

Thanks for the advice, if I can do it via jview that seems simple enough. Laura has helped me set up jview_v1 and seems to be running ok - is there any documentation?

I tried to do vertical interpolation with various different options on increments, 1st levels etc, but I always get an error message of the form:

Error: Specified Minimum/Maximum? is out of bounds
First specified level is: 0.00000
Last specified level is: 118360.
Allowable data range is: [ 0.00000, 50.0000]
Error: Cannot Convert this field - Returning

If you have any advice I'd be very grateful.

Best Wishes,


comment:6 Changed 13 years ago by lois

Hello Caroline, Chang's advice about JView is that whenever you enter a value in the GUI you need to press return. This way you will get the right values of max min and intervals etc

The documentation for JVIEW is here

we will copy this to the NCAS CMS page soon.


comment:7 in reply to: ↑ description Changed 13 years ago by sws04jc


If you wanted to write a modset, then you might like to know that geostrophic wind IS computed internally in the routine pmsl2a.f (CALC_PMSL). The calculation is only performed at the first model level, but you could expand on it to suit your needs.


Replying to

Hello NCAS,

Is there a quick way of getting geostrophic winds out of the UM?


comment:8 Changed 13 years ago by cbain

Hi - I solved this problem through that other ticket on density, so you can close it if you want. If I had more time I'd maybe get into modsets but it's not my priority right now, plus it's easy enough to do it in an outside program

Thanks for all your advice,


comment:9 Changed 13 years ago by jeff

  • Resolution set to fixed
  • Status changed from new to closed
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