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Pete, No, I didn't. With your plots, I just did some more checking... Approximating your curve, I got similar results using GRB data from amazon. However, when I switch back to approximating the curve on https://www.star.nesdis.noaa.gov/GOES/GOES16_FullDisk_Band.php?band=07&length=24 and plotting, my image again appears warmer. How do your plots compare to what's on the star site? Thanks... Art > From: "Pete Pokrandt" <poker@xxxxxxxxxxxx> > To: "ARTHUR AUGUST PERSON" <aap1@xxxxxxx> > Cc: "ldm-users" <ldm-users@xxxxxxxxxxxxxxxx> > Sent: Wednesday, January 24, 2018 10:48:46 PM > Subject: Re: [ldm-users] Problem calculating GOES-16 brightness temperature > from > radiance > Art, > Did you ever get this figured out? I plotted up an ABI full disk image from > the > GRB Radiance data coming in from both the Unidata DIFAX feed and from the > tiled > NOAAPORT CMI data. They seem pretty much the same to me, considering > resolution > differences - 2km for GRB vs 6km for the NOAAPORT data. > GRB image - [ > http://whirlwind.aos.wisc.edu/~wxp/goes16/test/201801210430_fulldisk_grb.jpg | > http://whirlwind.aos.wisc.edu/~wxp/goes16/test/201801210430_fulldisk_grb.jpg ] > NOAAPORT image - [ > http://whirlwind.aos.wisc.edu/~wxp/goes16/test/201801210430_fulldisk.jpg | > http://whirlwind.aos.wisc.edu/~wxp/goes16/test/201801210430_fulldisk.jpg ] > 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: ldm-users-bounces@xxxxxxxxxxxxxxxx <ldm-users-bounces@xxxxxxxxxxxxxxxx> > on > behalf of Arthur A Person <aap1@xxxxxxx> > Sent: Monday, January 15, 2018 4:45 PM > To: ldm-users > Subject: Re: [ldm-users] Problem calculating GOES-16 brightness temperature > from > radiance > All -- > I'm starting to think there may be a problem with the GOES-16 channel 7 GRB > NetCDF data. I wrote a short test code > (included below) that calculates brightness temperature and produces a png > file > with an abbreviated color table for comparison > with the NESDIS https://www.star.nesdis.noaa.gov/GOES/GOES16_CONUS.php > imagery. > When using the channel 7 data, > the calculated imagery appears noticeably warmer, but when using channel 14 > data > (for example), the images appear > very close in value. > Would someone else mind taking a look at this and confirm whether this might > be > the case, or whether I'm just losing my mind? > Thanks! > Art > _________________________________________________________________________________________________________ > from netCDF4 import Dataset > import numpy as np > import matplotlib.pyplot as plt > from matplotlib.colors import LinearSegmentedColormap > filename = > "amazon/OR_ABI-L1b-RadC-M3C07_G16_s20180151547235_e20180151550019_c20180151550058.nc" > #filename = > "amazon/OR_ABI-L1b-RadC-M3C14_G16_s20180151547235_e20180151550008_c20180151550050.nc" > dataset = Dataset(filename,'r') > # Get coefficients for calculation of brightness temperature > planck_fk1 = dataset.variables['planck_fk1'][:] > planck_fk2 = dataset.variables['planck_fk2'][:] > planck_bc1 = dataset.variables['planck_bc1'][:] > planck_bc2 = dataset.variables['planck_bc2'][:] > print("planck_fk1: ",planck_fk1) > print("planck_fk2: ",planck_fk2) > print("planck_bc1: ",planck_bc1) > print("planck_bc2: ",planck_bc2) > # Read the radiance data > rad = dataset.variables['Rad'][:] > dataset.close() > # Calculate brightness temperature > bt = ( (planck_fk2 / (np.log( (planck_fk1/rad)+1 ))) - planck_bc1 ) / > planck_bc2 > bt = bt - 273.15 > # Create a color table to compare against > https://www.star.nesdis.noaa.gov/GOES/GOES16_CONUS.php imagery > red = [] > green = [] > blue = [] > valmin=-110. > valmax=55. > red.append( [0.0, 0.0, 0.0] ) > green.append( [0.0, 0.0, 0.0] ) > blue.append( [0.0, 0.0, 0.0] ) > red.append( [ (-50.0-valmin)/(valmax-valmin), 0.0, 0.0 ] ) > green.append( [ (-50.0-valmin)/(valmax-valmin), 1.0, 1.0 ] ) > blue.append( [ (-50.0-valmin)/(valmax-valmin), 0.0, 0.0 ] ) > red.append( [ (-40.0-valmin)/(valmax-valmin), 0.0, 0.0 ] ) > green.append( [ (-40.0-valmin)/(valmax-valmin), 0.0, 0.0 ] ) > blue.append( [ (-40.0-valmin)/(valmax-valmin), 0.4, 0.4 ] ) > red.append( [ (-30.0-valmin)/(valmax-valmin), 0.0, 0.8 ] ) > green.append( [ (-30.0-valmin)/(valmax-valmin), 1.0, 0.8 ] ) > blue.append( [ (-30.0-valmin)/(valmax-valmin), 1.0, 0.8 ] ) > red.append( [ 1.0, 0.0, 0.0 ] ) > green.append( [ 1.0, 0.0, 0.0 ] ) > blue.append( [ 1.0, 0.0, 0.0 ] ) > cdict = {'red': red, 'green': green, 'blue': blue} > ctbl = LinearSegmentedColormap('custom', cdict) > # Set the figure size > fig = plt.figure(1, figsize=(23, 15)) > # Display the image > im = plt.imshow(bt, cmap=ctbl, vmin=valmin, vmax=valmax ) > # Display a color bar > cb = plt.colorbar( orientation='vertical', shrink=0.7, pad=0.01, aspect=30 ) > cb.set_label("Brightness Temperature (C)") > # Save the image to a png file > plt.savefig('plot.png', dpi=100) >> From: "Pete Pokrandt" <poker@xxxxxxxxxxxx> >> To: "ARTHUR AUGUST PERSON" <aap1@xxxxxxx> >> Cc: "ldm-users" <ldm-users@xxxxxxxxxxxxxxxx> >> Sent: Saturday, January 13, 2018 9:03:11 PM >> Subject: Re: [ldm-users] Problem calculating GOES-16 brightness temperature >> from >> radiance >> 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 | >> 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 > -- > 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
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