[gradsusr] Fwd: How to calculate the pressure gradient and geopotential height gradient?

[Jeff Duda]

To calculate the horizontal pressure gradient, you will need pressure on a
constant height surface.  If you have that, then the command to compute the
pressure gradient is

'define pgrad = cdiff(pres,x)/dx + cdiff(pres,y)/dy',


where the array holding pressure values is "pres" and you have defined dx
and dy as
'define dx = 6.371e6*cos(lat*3.14159/180)*cdiff(lon*3.14159/180,x)'
'define dy = 6.371e6*cdiff(lat*3.14159/180)'

where the 3.14159/180 term is used to translate degrees to radians.

To calculate the geopotential height gradient, you need height on a
constant pressure surface.  If you have that, then the command to compute
the geopotential height gradient is

'define gphgrad = cdiff(gheight,x)/dx + cdiff(gheight,y)/dy'

where the same commands as above were used to define dx and dy.

Jeff Duda


On Thu, Apr 4, 2013 at 7:02 AM, Simona Skyraite <skyraite at gmail.com> wrote:

>
>
> Hello,
>
> How to calculate pressure gradient (hPa/100 km) and geopotential height
> gradient? Could someone explain step by step how to do that?"
>
>
> Thanks in advance!
> Simona
>
>
>
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>


-- 
Jeff Duda
Graduate research assistant
University of Oklahoma School of Meteorology
Center for Analysis and Prediction of Storms
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