Pete, Here's what I see in the imagery you provided: Examining the cloud feature in the Bay of Campeche for channel 13, the AOS image shows bright greens to a peak near orange which I would value in a range from 215 to 230 K (-58 to -43 C) using the AOS scale. For the NESDIS image, the colors range from navy blue to moderately bright green. Using the NESDIS scale you attached, I would value that range from -55 to -40 C. The difference between these two images is about 3 C which I would attribute to the limits of the subjective evaluation of the color ranges. Doing the same for channel 7, the AOS image shows light blues to navy blue which I would value in a range from 242 to 252 K (-31 to -21 C) using the AOS scale. For the NESDIS image, the colors range from light blue (or even starts in the gray) to navy blue or a range of about -40 to -25 C. The warmer end of this range is within the limitations of guessing at the color values, but the colder end is about 10 C different. Put another way, both the AOS and NESDIS images show about the same color for the coldest clouds (navy blue), but navy blue on the AOS curve is about 243 K (-30 C) versus -40 C for the NESDIS curve. The difference is more apparent when you replicate the NESDIS curve and plot the images comparing them side by side. I've attached channel 7 imagery from NESDIS and also what I created from the GRB data for 14:27Z this morning to show what I mean (although there's not a lot of high cloud out there today). The ColorBar image applies to the NESDIS image and I've tried to replicate that in my image. I'm convinced there's a difference in what's being shown on the NESDIS site versus what we're calculating from the GRB data... but why? It only appears to be channel 7 related, although I haven't looked at other channels besides 13 (which you provided here) and 14. Art > From: "Pete Pokrandt" <poker@xxxxxxxxxxxx> > To: "ARTHUR AUGUST PERSON" <aap1@xxxxxxx> > Cc: "ldm-users" <ldm-users@xxxxxxxxxxxxxxxx> > Sent: Thursday, January 25, 2018 5:20:24 PM > Subject: Re: [ldm-users] Problem calculating GOES-16 brightness temperature > from > radiance > Art, > It's a little hard, since we are using slightly different color tables. > The NESDIS color table (attached) first uses color - cyan- at -30C (243K) and > then goes through a rainbow color table up to about -70C (203K) and then black > to white. > My color table, based on what I had seen CIMSS using, first uses cyan at 253K > (-20C) and cycles through colors up to about 203K (also -70C). > These same color tables are used for all of the IR images except the WV (so > ABI > 7 and 11-13) > I've attached copies of the NESDIS and UW-AOS versions of both channels 7 and > 13, all valid at 1930 UTC today, and the color table used by NESDIS since > theirs are not on the image like mine are - and also an image from last April > showing the IR color table that CIMSS used that I was trying to re[produce - > although now that I look, I think my purple should go to 183K, not 180. That > might be a bug for me, but only on the most cold temps. > A visual comparison of both of these - their ABI7 to mine, and their ABI13 to > mine - looks like we're the same, just using a different color scale.. > I also attempted to overlay their color scale with mine so the temps lined up > (AOS_Color_Table_vs_NESDIS.png). The differences in our color scales would be > most evident at warmer temps - so maybe they are more prominent at ABI 7 which > is warmer than ABI 13 or 14, which are colder? > Thoughts? > 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: Thursday, January 25, 2018 8:04 AM > To: Pete Pokrandt > Cc: ldm-users > Subject: Re: [ldm-users] Problem calculating GOES-16 brightness temperature > from > radiance > 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 -- 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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