[ncl-talk] Question about wrf_user_getvar cloud-top temperature(ctt) calculation

[Dennis Shea]

Generally, NCL's wrf_* functions are direct interfaces to the fortran
subroutines written by members of the WRF project. NCL developers did not
write the WRF or RIP subroutines.

Likely, the answer to your questions would have to come from a WRF support
group.

One possible group is *here* <https://forum.mmm.ucar.edu/phpBB3/>

*Good Luck*



On Thu, Nov 19, 2020 at 6:39 AM Nan Yang via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hello,
>
> I am using wrf_user_getvar to calculate cloud top temperature (ctt) from
> WRF outputs.
> I've checked the wrf_fctt.f source code. The cloud-top temperature is
> calculated by interpolating the temperature to the level of unit optical
> depth (or a threshold) into the cloud, similar to RIP, but the absorption
> cross-section for cloud ice and cloud water are obtained from Dudhia (1989)
> in RIP, while in ncl:
> ABSCOEFI = .272D0  ! cloud ice absorption coefficient in m^2/g
> ABSCOEF = .145D0   ! cloud water absorption coefficient in m^2/g
> I want to know why ctt is calculated this way, and where the constants
> come from.
> Is there any reference paper for the ncl wrf_ctt calculation?
>
> Thanks,
>
> Nan Yang
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