[gradsusr] How to calculate ∂/∂(ln p) of a variable in grads

[Jeff Duda]

Mano,
I would think it would suffice to create a new pressure field, ln p, as
follows:

'define lnp = log([pres])'  [whatever your 3D pressure field is named]

Then compute your vertical derivative using manual centered differences
(I'm not sure if the cdiff() function does this properly...it might work,
but you have to be careful with the top and bottom bounds):

(Make sure to adjust your dimension environment accordingly)

'd [Vg](z+1) - [Vg](z-1) / (lnp(z+1) - lnp(z-1))'  [whatever your
geostrophic wind field is named]

If using cdiff, it should be about as simple as 'd cdiff([Vg],lnp)'

Jeff Duda

On Mon, Mar 30, 2020 at 2:38 AM lpasmanoranjan <lpasmanoranjan at gmail.com>
wrote:

> Dear Users,
> I would like to calculate  thermal wind from geostrophic wind in grads.
> Following is the formula:
> Thermal Wind, Vt=  ∂Vg / ∂(ln p)
> where Vg is the geostrophic wind, p is the pressure
>
> I can't able to calculate the term  ∂ / ∂(ln p).
>
> Any suggestions or help?
> Thank you.
> --
> Kind Regards,
> Mano
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-- 
Jeff Duda, Research Scientist
University of Colorado Boulder
Cooperative Institute for Research in Environmental Sciences
NOAA/OAR/ESRL/Global Systems Division
Boulder, CO
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