Pete,
By default, netCDF4-python applies the scale and offset when you read in
the data. This can be disabled by calling `set_auto_scale()` on individual
variables or on the Dataset itself.
Ryan
On Sat, Jan 13, 2018 at 7:03 PM, Pete Pokrandt <poker@xxxxxxxxxxxx> wrote:
> Forgot to cc to the list.
>
> Here's a commented version of the script that I'm currently using to plot
> ABI channel 13 (clear channel IR window) but the calculation for BT should
> work for any of the channels 7-16.
>
> I am using just the radiance values read in from the netcdf files, without
> applying any scale/offset to them. Perhaps the netcdf4 read does that for
> us? I am reading the scale and offset info in for reference, and printing
> them out, but I am not using them in my calculations at all.
>
> If for some reason, the attachment doesn't come through, you can get the
> file at
>
> http://sysadm.aos.wisc.edu/~poker/goes16_GRB_fulldisk_IR13_ircm.py
>
> Hope this helps,
> Pete
>
>
>
> <http://www.weather.com/tv/shows/wx-geeks/video/the-incredible-shrinking-cold-pool>
> --
> Pete Pokrandt - Systems Programmer
> UW-Madison Dept of Atmospheric and Oceanic Sciences
> 608-262-3086 <(608)%20262-3086> - poker@xxxxxxxxxxxx
>
>
> ------------------------------
> *From:* Arthur A Person <aap1@xxxxxxx>
> *Sent:* Saturday, January 13, 2018 9:04 AM
> *To:* Pete Pokrandt
> *Cc:* ldm-users
>
> *Subject:* Re: [ldm-users] Problem calculating GOES-16 brightness
> temperature from radiance
>
> 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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--
Ryan May, Ph.D.
Software Engineer
UCAR/Unidata
Boulder, CO
