Ryan,
Perfect, thanks for the explanation!
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 - poker@xxxxxxxxxxxx
________________________________
From: Ryan May <rmay@xxxxxxxx>
Sent: Monday, January 15, 2018 2:00 PM
To: Pete Pokrandt
Cc: Arthur A Person; ldm-users
Subject: Re: [ldm-users] Problem calculating GOES-16 brightness temperature
from radiance
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<mailto: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<tel:(608)%20262-3086> -
poker@xxxxxxxxxxxx<mailto:poker@xxxxxxxxxxxx>
________________________________
From: Arthur A Person <aap1@xxxxxxx<mailto: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<mailto:poker@xxxxxxxxxxxx>>
To: "ARTHUR AUGUST PERSON" <aap1@xxxxxxx<mailto:aap1@xxxxxxx>>, "ldm-users"
<ldm-users@xxxxxxxxxxxxxxxx<mailto: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<mailto:ldm-users-bounces@xxxxxxxxxxxxxxxx>
<ldm-users-bounces@xxxxxxxxxxxxxxxx<mailto:ldm-users-bounces@xxxxxxxxxxxxxxxx>>
on behalf of Arthur A Person <aap1@xxxxxxx<mailto:aap1@xxxxxxx>>
Sent: Friday, January 12, 2018 7:43 AM
To: ldm-users@xxxxxxxxxxxxxxxx<mailto: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<http://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<mailto:aap1@xxxxxxx>, phone:
814-863-1563<tel:(814)%20863-1563>
--
Arthur A. Person
Assistant Research Professor, System Administrator
Penn State Department of Meteorology and Atmospheric Science
email: aap1@xxxxxxx<mailto:aap1@xxxxxxx>, phone:
814-863-1563<tel:(814)%20863-1563>
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