[ncl-talk] (no subject)

Guido Cioni guidocioni at gmail.com
Thu Apr 20 15:04:10 MDT 2017

```Hi,
given height levels you can derive pressure without temperature using an approximation. Function http://ncl.ucar.edu/Document/Functions/Crop/prsatm_z_fao56.shtml <http://ncl.ucar.edu/Document/Functions/Crop/prsatm_z_fao56.shtml> (requires NCL 6.4.0).

Having pressure and theta you can easily derive temperature using the definition Theta=T*(Psfc/P)^(Rd/cp).

It won’t be perfect given that you are not using temperature to derive pressure but shouldn’t be far off if you are below 30km and in normal conditions.

Cheers

> Il giorno 20 apr 2017, alle ore 22:45, steve kirby <thinjogger at gmail.com> ha scritto:
>
> Hi,
>
> My goal is to use:
>
> skewT_PlotData()
>
> but I only have a surface pressure and potential temperature, and then
> potential temperature and wind dir and wind spd at many height levels.
>
>  I am wondering if there is any way via NCL to derive temperature and/or
> pressure with height given this information.  It seems
> with either the hypsometric or Poisson's equation I am lacking at least one parameter.
>
> Hypsometric: P = Psfc * e**(-z/H)
>    Have z and Psfc, and if one uses the approximation for scale height, H =
> 29.3 *  Tvirtual, then Tvirtual = (1 + 0.61w) * T; I have w, however I
> don't have T.
>
> Poisson's: Theta = T * (Psfc/P)**0.286
>    Have Theta (potential T) and Psfc, but no T or P.
>
> But perhaps there is a way?
>
> TIA,
> Steve
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