Art,
This is all I have in my NCL code to compute brightness temp from IR
channels on G16. Very short. Each channel's data is coming into my
subroutine as the variable called "raw_data." It's possible that NCL is
doing something internal with the netCDF variables themselves to 'scale'
the data based on internals of NCL that I don't know about.
fk1 = infile->planck_fk1
fk2 = infile->planck_fk2
bc1 = infile->planck_bc1
bc2 = infile->planck_bc2
g16_output_data = (fk2/(log((fk1/(raw_data))+1))-bc1)/bc2 - 273.15
Greg Thompson, NCAR-RAL
On Sat, Jan 13, 2018 at 8:04 AM, Arthur A Person <aap1@xxxxxxx> wrote:
> Pete,
>
> Thanks for the help. Actually, I already tried adding parens to the
> equation, including the variation you
> suggested, but the results are the same. Do you have a few lines of code
> that worked for you that you'd
> be willing to share? Or, do you recall whether there's any issue with
> netCDF auto-scaling the input data,
> or any units conversion that has to be included that's not in the
> documentation?
>
> Thanks... Art
>
>
> ------------------------------
>
> *From: *"Pete Pokrandt" <poker@xxxxxxxxxxxx>
> *To: *"ARTHUR AUGUST PERSON" <aap1@xxxxxxx>, "ldm-users" <
> ldm-users@xxxxxxxxxxxxxxxx>
> *Sent: *Friday, January 12, 2018 11:47:08 AM
> *Subject: *Re: [ldm-users] Problem calculating GOES-16 brightness
> temperature from radiance
>
> Art,
>
>
> I think it may be a parenthesis/order of operations issue. I seem to
> recall having this same issue when I first started working with the GRB
> data.
>
>
> Try this:
>
>
> bt = ( planck_fk2 / ( np.log((planck_fk1 / rad) + 1 )) - planck_bc1) /
> planck_bc2
>
>
> Pete
>
>
>
>
> ------------------------------
> *From:* ldm-users-bounces@xxxxxxxxxxxxxxxx <ldm-users-bounces@unidata.
> ucar.edu> on behalf of Arthur A Person <aap1@xxxxxxx>
> *Sent:* Friday, January 12, 2018 7:43 AM
> *To:* ldm-users@xxxxxxxxxxxxxxxx
> *Subject:* [ldm-users] Problem calculating GOES-16 brightness temperature
> from radiance
>
> Hi...
>
> I'm trying to calculate brightness temperature from radiance for GOES-16
> IR channel 7 using rebroadcast data
> but my values compared to McIDAS imagery are coming out 15 to 20 degrees C
> too warm. I'm using the following
> values and code:
>
> Test imagery: OR_ABI-L1b-RadC-M3C07_G16_s20180112232223_e20180112235008_
> c20180112235045.nc
>
> rad (radiance) is read in from and auto-scaled by netCDF,
> planck_fk1: 202263.0
> planck_fk2: 3698.18994140625
> planck_bc1: 0.4336099922657013
> planck_bc2: 0.9993900060653687
>
> bt = ( planck_fk2 / np.log( (planck_fk1/rad)+1 ) - planck_bc1 ) /
> planck_bc2
> bt = bt - 273.15
>
> Can anyone tell me if I'm missing a step or spot a dumb mistake?
>
> Thanks... Art
>
> --
> Arthur A. Person
> Assistant Research Professor, System Administrator
> Penn State Department of Meteorology and Atmospheric Science
> email: aap1@xxxxxxx, phone: 814-863-1563 <(814)%20863-1563>
>
>
> --
> Arthur A. Person
> Assistant Research Professor, System Administrator
> Penn State Department of Meteorology and Atmospheric Science
> email: aap1@xxxxxxx, phone: 814-863-1563 <(814)%20863-1563>
>
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