Re: [ferret_users] Manually interpolate zero degree level

[Russ Fiedler <russell.fiedler@xxxxxxxx>]

Hi,

I think Jasper actually wants @WEQ rather than @LOC since his 
independent height variable is pressure not geopotential height.

http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/XPRESSIONS#_VPID_175


let isotherm_0 = temp[z=@WEQ:0]  ! pressure kernel at 0 degrees
let integrand_0 = geopotential*isotherm_0/9.81  !
let/title="geopotential height on 0 degree isotherm" z_g_0 = 
integrand_0[z=@sum]  ! interpolated Z_g


Cheers,
Russ

On 18/05/17 05:17, Ansley C. Manke wrote:
> Hi,
>
> Look at the transformation @LOC which picks out the data at a 
> specified value.
>
> -Ansley
>
>
> On 5/17/2017 6:14 AM, Jasper Denissen wrote:
> > Dear ferret users,
> >
> > I've got two variables, temperature T (K) and geopotential Z 
> > (m^2/s^2) on 25 pressure levels and a certain spatial extent. What I 
> > want to do is find the exact (read linearly interpolated) height of 
> > the zero degree level. All I found in the ferret documentation was 
> > interpolate transformations which fill data gaps, but I just need to 
> > define one variable which contains the interpolated geopotential 
> > height (geopotential / 9.81) at which the interpolated temperature 
> > equals zero. If there are several heights where T = 0, please take 
> > the lowest height.
> >
> > I think this should be a fairly simple transformation, but I can't 
> > seem to find the answer myself. Someone please help me!
> >
> > Kind regards,
> >
> > Jasper Denissen
> > MSc student Earth & Environment
> > Wageningen University