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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
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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 - 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@xxxxxxxxxxxxxxxx> 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 -- Arthur A. Person Assistant Research Professor, System Administrator Penn State Department of Meteorology and Atmospheric Science email: aap1@xxxxxxx, phone: 814-863-1563
Attachment:
goes16_GRB_fulldisk_IR13_ircm.py
Description: goes16_GRB_fulldisk_IR13_ircm.py
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