An update on the NSIDC satellite sensor issue

I missed this June 2nd NSIDC announcement while traveling this week, but here it is now, just a few days late. For those of you that have been inquiring about the status of the NSIDC sea ice plot, this should help answer some of those questions. The fact that they have done parallel data keeping from F17 for a year to gauge differences is the right way to do it. I wish NOAA would do the same thing for weather stations when they convert from Stevenson Screens to MMTS, or when they move a station, as it would help detect and minimize siting induced offsets that now make it into the temperature record.  – Anthony


NSIDC has transitioned from the Defense Meteorological Satellite Program (DMSP) F13 satellite, to the DMSP F17 satellite. Switching to the new satellite will allow us to continue our consistent long-term record of sea ice extent.

map from space showing sea ice extent, continents

High-resolution image Figure 1. NSIDC now has more than a year of data from the Special Sensor Microwave Imager/Sounder (SSMIS) sensor on the DMSP F17 satellite, which has been intercalibrated with data from the F13 satellite. Note the close correspondence between the two data records. The average absolute daily difference was approximately 28,000 square kilometers (11,000 square miles).

Sea Ice Index data. —Credit: National Snow and Ice Data Center

Please note that our daily sea ice images, derived from microwave measurements, may show spurious pixels in areas where sea ice may not be present. These artifacts are generally caused by coastline effects, or less commonly by severe weather. Scientists use masks to minimize the number of “noise” pixels, based on long-term extent patterns. Noise is largely eliminated in the process of generating monthly averages, our standard measurement for analyzing interannual trends. Data derived from Sea Ice Index data set.

Continuing a long-term data series

The DMSP F13 satellite that has been central to our Arctic sea ice analysis for the past several years is nearing the end of its mission and is no longer a reliable resource for our sea ice products. As is standard data practice, we have transitioned to a newer sensor.

NSIDC now has more than a year of data from F17, obtained from the NOAA Comprehensive Large Array-data Stewardship System (CLASS). While the sensors on the two satellites are slightly different, they use the same microwave frequencies to collect sea ice data; by comparing a year of F17 data with a year of F13 data, we have been able to calibrate F17 to ensure its measurements are consistent with the prior F13 record. F13, in turn, had been similarly calibrated with prior generations of sensors, resulting in a consistent, long-term record of sea ice extent since 1979. The average absolute daily difference between data from F13 and F17 was approximately 28,000 square kilometers (11,000 square miles).

For more information on the satellite sensors that NSIDC uses for sea ice data, see our February 26 update. For detailed information on the near-real-time sea ice data, please read the data set documentation.

27 thoughts on “An update on the NSIDC satellite sensor issue

  1. So the F13 has been faltering for some time, it had sensor problems since January 2009 … and yet the F17 data matches the F13 data consistently. Even for the stretch of January 2009 to May 2009. I’m flabbergasted. Obviously there’s no need to transition from the F13 after all! Talk about a wasted effort. /sarc
    REPLY: When doing such a comparison, I’m sure they removed obviously bad data. It is relatively easy to tag it since the F13 issue is well known. I suspect this represents that, but it is a good question for NSIDC to address. – Anthony

  2. About the sea-ice what caused the recent steep drop in the graph this site links to almost like someone tied a lead weight to it?
    I know from the Cryosphere images last I checked there were some low ice percentage regions still counting as ice extent, maybe those areas melted or were blown out to warmer waters further south?

  3. [snip]
    Given the personal attacks you have made about me and others over at Climate Progress, and your apparent endorsement of comments advocating violence as well as the term “denier” in the offensive context of “holocaust denier”, after 66 comments over several weeks, your commentary as “dhogaza” is no longer welcome here.
    That being said, you are welcome to post all the insults, commentary, or personal attacks you wish using your real name. Be a man, instead of a phantom, and stand behind your words.
    If you truly are a man of your word, fully believing what you say, it shouldn’t be a problem.
    – Anthony Watts

  4. Adam from Kansas (10:31:36) :
    About the sea-ice what caused the recent steep drop in the graph this site links to almost like someone tied a lead weight to it?
    I know from the Cryosphere images last I checked there were some low ice percentage regions still counting as ice extent, maybe those areas melted or were blown out to warmer waters further south?

    According to the NSIDC web site, it is “winds and temperature.” See their detailed 6/03/09 Report at http://nsidc.org/arcticseaicenews/.

  5. While IARC-JAXA uses the AMSR-E on board the Aqua satellite, NSIDC continues its reliance on the DMSP-series of satellites, now finally using the latest in the series, the F17. I can understand their continuing reliance on this series; I suppose that there’s an F18 waiting in the wings to be launched in the near future. And while it’s nice to have a second measuring standard in place (Aqua), I wonder what its lifespan is projected to be and if there are plans to also launch a future replacement for it.
    While I’ve noticed a number of comments about how quickly the ice has melted during the latter part of May, this shouldn’t really be surprising as this is first-year ice. There’s more second and multi-year ice this year then last, so the interesting part of the melt won’t show until August when the ice melt rate slows and then we’ll see what it all looks like in September. Whatever happens will have less to do with air temp and more to do with storms, sea currents, and sea temps.

  6. I agree with those who are skeptical.
    If the previous F13 data was questionable – –
    why are they matching F17 data to it?
    (Unless, of course, that is their intent)

  7. dhogaza (11:20:44) :

    [dhogaza:] [snip]
    [anthony:] Given the personal attacks you have made about me and others over at Climate Progress, ….
    That being said, you are welcome to post all the insults, commentary, or personal attacks you wish using your real name. Be a man, instead of a phantom, and stand behind your words.

    I try to stay above the fray and remain away from ad hominem attacks. However, I do make exceptions, dhogaza, and you’re one of them. This is probably my first reply to one of your posts where I “attack the man”. From what I’ve read from your special pedestal at Climate Progress, you are a first class jerk and I look forward to being able to say that to your Real Name.
    If you do think anything you post here in the future will be taken with any sort of respect, you are also a first class fool. I humbly suggest you stay at CP and take your potshots from there.

  8. Katherine (10:30:32) :
    So the F13 has been faltering for some time, it had sensor problems since January 2009 … and yet the F17 data matches the F13 data consistently. Even for the stretch of January 2009 to May 2009. I’m flabbergasted. Obviously there’s no need to transition from the F13 after all! Talk about a wasted effort. /sarc

    The problem was always with the ‘near real-time’ data which is displayed on the website. Missing swathes/fragments from one pass of the satellite can be rectified off line from the next orbit (twice/day). For real time data you need a satellite that doesn’t require such correction. The F13 satellite was starting to drift as it aged so they replaced its data with that from its successor F15 which worked fine until the Navy switched on some hardware onboard which completely screwed up F15 (as I recall the 22GHz channel was knocked out)! As the next satellite, F17, wasn’t yet fully commissioned it was necessary to go back to F15 until the calibration of F17 was completed and it could be used for realtime data.
    REPLY: When doing such a comparison, I’m sure they removed obviously bad data. It is relatively easy to tag it since the F13 issue is well known. I suspect this represents that, but it is a good question for NSIDC to address. – Anthony
    They addressed this when the first problems with F15 surfaced, Meier even posted on here about it.

    REPLY:
    When I said ” it is a good question for NSIDC to address.” I meant in the current context of their announcement. One of the ongoing problems with presenting science to the public is a lack of greater context and history, making it more difficult for the layman to understand. – Anthony

  9. Sorry there’s a typo in the above post it was F15 that was ‘screwed up’, can you please fix it? Thanks
    REPLY: Done – Anthony

  10. Leon Brozyna (12:40:06) :
    While IARC-JAXA uses the AMSR-E on board the Aqua satellite, NSIDC continues its reliance on the DMSP-series of satellites, now finally using the latest in the series, the F17. I can understand their continuing reliance on this series; I suppose that there’s an F18 waiting in the wings to be launched in the near future. And while it’s nice to have a second measuring standard in place (Aqua), I wonder what its lifespan is projected to be and if there are plans to also launch a future replacement for it.

    There are currently several DMSP satellites in operation, the launch of F18 was delayed from last year to possibly this August because of the extraordinary longevity of the platforms, the original design life was 4 years, F13 is still functioning after ~14 and is the designated backup to F17, F16 is ultimately to be replaced by F18.
    The AMSR-E is a Japanese design and its replacement will presumably be decided by the Japanese, it’s currently ~6yo I think.

  11. Phil. (13:23:50) :
    Thanks for the info about F18.
    As for Aqua, there are several instrument packages aboard the Aqua satellite: AMSR-E (Japan), HSB (Brazil), MODIS, AMSU-A, AIRS, and CERES (not sure if these last four are NASA/NOAA programs or not).
    So NSIDC sticks with the DMSP satellite program – it’s no wonder, it’s a single agency (NOAA) program – one has to wonder about the future of Aqua. Will NASA keep the program in place? Will other nations continue to take part in it (such as Japan)? When politics (funding concerns, national interests, etc.) and science mix, a degree of uncertainty and compromise is involved. Plus, Aqua is just one of several satellites in the Earth Observing System (EOS) which also include Terra, Aura, CALIPSO, CloudSat, and PARASOL (France). Looks like science isn’t as simple as we’d like it to be.

  12. Anthony I have a question… how does cryosphere get this current daily image taken 06/04/2009 http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png
    from this http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/ARCHIVE/20090604.jpg
    I understand the satelite is messing up.. ignore the central ice mass, the edges are where the real difference hits, particularly in the “Barents sea”. It would seem that they are correcting the edges somehow? I suspect this is how intrepid explorers get the impression that open water exists where there is still ice.
    Thanks to one of your readers for teaching me this trick… even if they dont show the image in their archive page, they still save a jpg of it to its date in the archive folder:) I guess im just not understanding why in the archive jpg, the ice is shown as solid, and in the main site page.. its water and thin ice.

  13. pkatt (15:45:40) :
    Anthony I have a question… how does cryosphere get this current daily image taken 06/04/2009 http://arctic.atmos.uiuc.edu/cryosphere/NEWIMAGES/arctic.seaice.color.000.png

    This is a high resolution image from the AMSR-E satellite
    from this http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/ARCHIVE/20090604.jpg
    This is an image from the SSMI imager on board the F15 satellite (used in the archives to maintain consistency with the past images, unfortunately no longer gives usable images which is why CT doesn’t link to it.) It’s also why CT display the following message if you try to compare images (if you go the back door route you don’t see it):
    “February 25, 2009 – The SSMI images for many days in 2009 were bad enough that we removed them from this comparison display (see note below and the NSIDC website). There is enough interest in these side-by-side comparison images that we will try to replace them with corresponding images from the AMSR-E sensor in the coming weeks.”

  14. Got to admit Anthony that however much your attempts to educate dhogaza are well-meaning and justified, a wee bit of me does hope that you fail. He’s such an intemperate cad, at times, I’m reminded of the archetypical literary villain- Flashman. However much we despair of his misbehaviour we still love his uncanny ability to justify irrational sentiments and prejudices with toadying genuflexions to figures of authority!
    Dhogoza- we love you-trolly(sic) we do

  15. Phil. (16:26:22) :
    “This is a high resolution image from the AMSR-E satellite”
    Not a minor nitpick, these are not images, but maps generated from algorythms.
    Nansen compares SSMI and AMSR:
    http://arctic-roos.org/observations/satellite-data/sea-ice/Arctic-ice-concentration-maps-from-SSMI-and-AMSRE
    Concerning archived data, Nansen and NSIDC both show about the same current extent, but vary significantly in the 2007 line. Nansen shows current 2007 (June 4-5) to be around 500K less than NSIDC:
    http://nsidc.org/data/seaice_index/images/daily_images/N_timeseries.png
    http://arctic-roos.org/observations/satellite-data/sea-ice/ice-area-and-extent-in-arctic

  16. Phil:
    I am not certain where you found a reference that gave SSM/I a 4 year design life. Having helped build them, and TMI my marching orders were for a 3 year mission which all but one sensor handsomely exceeded. Curiously, the failed sensor was brought down by an design attitude that said it was only a 3 year mission, anything can do that. We returned to a more robust mechanical design and the rest as they say is history, Its been great seeing these old birds working their hearts out. A big thank you goes out to Anthony et al for working to keep the users of the data honest. – John

  17. “Special Sensor Microwave Imager/Sounder (SSMIS) sensor on the DMSP F17 satellite, which has been intercalibrated with data from the F13 satellite.”
    Nope, can’t see a problem here. Use a failing sensor to cal a new one.
    “Note the close correspondence between the two data records.”
    Nothing up my sleeve…Presto! They match.
    Give me a break. They need to switch to a SAR sensor.

  18. John (17:28:59) :
    Phil:
    I am not certain where you found a reference that gave SSM/I a 4 year design life. Having helped build them, and TMI my marching orders were for a 3 year mission which all but one sensor handsomely exceeded. Curiously, the failed sensor was brought down by an design attitude that said it was only a 3 year mission, anything can do that. We returned to a more robust mechanical design and the rest as they say is history, Its been great seeing these old birds working their hearts out. A big thank you goes out to Anthony et al for working to keep the users of the data honest. – John

    It was in ‘Spaceflight Now’, http://www.spaceflightnow.com/atlas/av017/081006delay.html
    “The present-generation DMSP satellites were built with a four-year design life, yet most have been lasting eight years or more.
    “We upgraded F15 and F16 with Single Gyro software to extend satellite life with improved attitude control. Further, both F15 and F16 were built with solid state recorders which replaced the old analog recorders that were life-limiting items on prior DMSP satellites,” program officials said.”
    Glenn (17:26:54) :
    Phil. (16:26:22) :
    “This is a high resolution image from the AMSR-E satellite”
    Not a minor nitpick, these are not images, but maps generated from algorythms.

    Actually they are images, just like MRIs are images and PET scans produce images.

  19. The sad individual who posts under the screen name ‘dhogaza’ leaves his trail of excrement all over numerous climate related blogs.
    His recent befouling of Climate Progress is typical of his ‘big man on-line’ behaviour.
    As soon as he appears in a comment thread I just hit the close button no matter how important the original post – it’s just not worth wading through his waist deep [excrement] to find reasonable and informed comments.
    He thinks his trivial contributions play an important part in fighting the good fight for the ‘carbon is pollution’ crowd, but instead he devalues otherwise generally commendable blogs like Climate Progress and turns them into unreadable effluent.
    The comparison between the tone here and the blogs to which he has seemingly unfettered access is remarkable and I’d like to thank Anthony and his moderators for keeping it so.

  20. I think I know who “Darth” dhogaza is, I shall make some inquiries….
    REPLY: no need, already known, but thanks. – Anthony

  21. O/T -sort of…
    This is a layman’s question.
    I’ve been looking at the AMSRE_Sea_Ice_Extent graph and noticed at about the beginning of June there is an increase in sea ice extent most years. It just curiosity really but what is the phenomenon which causes that?

  22. Neil,
    Straight from the IARC-JAXA site:
    “The current version of data processing produces an erroneous blip of sea-ice extent on June 1 and October 15, which is seen in the graph of sea-ice extent as a small peak on these dates. The apparent blip arises due to switching of some parameters in the processing on those dates. The parameter switching is needed because the surface of the Arctic sea ice becomes wet in summer due to the melting of ice, drastically changing the satellite-observed signatures of sea ice. We will soon improve the processing to make the graph much smoother.”

  23. Neil Jones (00:12:42) :
    “’ve been looking at the AMSRE_Sea_Ice_Extent graph and noticed at about the beginning of June there is an increase in sea ice extent most years. It just curiosity really but what is the phenomenon which causes that?”
    This was well answered a couple of months back by the Japanese agency. On June 1, they switch to a different algorithm for to account for the development of melt water on the ice surface so as not to be calculated as open sea water.

  24. Interesting that the “algorerythm” used to analyze ice area is deliberately skewed (manipulated) on a specific calendar date every year (June 1) to account for a gradually changing ice and snow melt function in the Arctic that is NOT calendar dated.
    You’d figure that they will run into problems when (if) the data actually does begin changing: due to either rising or falling temperatures. Good to see that the program is actually being fixed.

  25. FredA & Arn Riewe
    Thanks for the answer, it’s always helps to know where to look for this information. As a layman, that’s not always the easiest thing to do.

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