[ncl-talk] Computation of Density from WRF outputs

Dennis Shea shea at ucar.edu
Sat Aug 17 10:15:58 MDT 2019

```[1] NCL is language focused.   Your comment/question:

",,,Qvapor, qcloud, qrain, qice, qgraupel. Do I need to account for all the
Qs? If so, how? I don’t suppose that I could just add them all up? Or is
only Qvapor relevant for kinetic energy computations in a Hurricane?"

[2] re: "How do we not have an in-built NCL function for computing NCL
I assume you mean:
"How do we not have a built-in NCL function for computing

====================
Ideal gas law:  p = (density)*RD*(temperature)
Hence:
density = p/(RD*temperature)

p   => Pa
qv  => kg/kg  :QVAPOR
qc =>  kg/kg  :QCLOUD
t => K

tv = t*(1+0.609*qv)
or, maybe
tv = t*(1+0.609*qv - qc)

RD    = 287.04         ; [J/(K-kg)] Gas Constant dry air
density = p/(RD*tv)

On Fri, Aug 16, 2019 at 1:40 PM Prashanth Bhalachandran via ncl-talk <
ncl-talk at ucar.edu> wrote:

> Dear NCL Experts,
> I have a question regarding the computation of density from the WRF
> outputs. I specifically need to compute it for kinetic energy (rho *
> u_i^2).
>
> Since density is not an output from WRF, I currently have:
>
> Rho = ((pressure*100.)) /((287.0 *(1. + (0.608*qvapor))*temperature)).
>
> However, I realize that there are Qvapor, qcloud, qrain, qice, qgraupel.
> Do I need to account for all the Qs? If so, how? I don’t suppose that I
> could just add them all up? Or is only Qvapor relevant for kinetic energy
> computations in a Hurricane?
>
> Also, how do we not have an in-built NCL function for computing NCL
>
> Sincerely,
> Prashanth
>
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