Post on 09-Jul-2020
Update on SSM/I PassiveMicrowave Products
Walt Meier
PoDAG, 15 October 2008
Part I – SSM/I-SSMIS Transition Issues
SSM/I Status
• F13 operational since 1995• F15 backup SSM/I for F13 since 1999
August 2006, RADCAL beacon turned on, resultedin corruption of 22 GHz signal
• F16 (2003), F17 (2006) flying SSMIS• Data stream from F17 started 26 March 2008• F13, F15 available from standard NSIDC
sources: NRT: NASA Marshall Final calibrated: RSS
• F16, F17 available NRT only through CLASS RSS working on their calibrated F16 and F17
SSM/I Status
• In early January 2008, F13 startedhaving data dropouts
• Became drastic by early March – largeregions of missing data
• NSIDC confirmed with NOAA/DoD thatit was due to recorders on F13 startingto fail - not a temporary issue
Immediate SSM/I alternatives
• F15 through same data stream fromMarshall Issue of RADCAL
• F16, F17 through CLASS (F17 databecame available 26 March 2008) SSMIS New source Completely different file structure, format Considerable time and resources needed
to investigate
F15 SSM/I
• Only 22 GHz channel affected byRADCAL beacon
• NSIDC investigated issue• Error is primarily an offset in the
brightness temperature• Could do a simple correction
F13 vs. F15, Stable Target – Central Greenland Tbs
F13 vs. F15 – Arctic multiyear ice
F13 vs. F15 Brightness TemperaturesF1
3 22
V
F13
19V
~10-12 K
Arctic sea ice, 13 June 2007
F15 22V F15 19V
F13 vs. F15 regression - Arctic
F13 vs. F15 regression - Antarctic
Approach to correction
• Brightness temperature regression Difficulties because there is substantial spatial and
temporal variability in regression coefficients Even using daily adjusted regression coefficients
had limited success• Tiepoint adjustment (and 22 GHz correction)
Iterate to minimize difference in ice extent fromF13 and F15 sensor – make F15 output consistentwith F13 output
Basically the same approach used by Goddard
F15 corrected sea ice extent/area
Bias = 200 sq km (<1 grid cell)St Dev = 13,000 sq kmMax Diff = 40,000 sq km
F13-F15 Extent Difference
Current processing plan
• Continue F15 NRT until issues with CLASSworked out for F17
• RSS now processing F15 with RADCALcorrection (since July) More sophisticated than NSIDC approach –
includes cross-swath correction Not ready for climate-record status OK for a weather filter?
• RSS working on F16 and F17
Current and future NRT and preliminary processing
• NSIDC acquiring F13 and F15 from RSS• One full year (2007) of overlap provided• Need to do intercalibration with RSS data (RSS
has 22 GHz correction)• Goddard will do final tiepoint adjustments as in
the past• NSIDC starting F15 processing of RSS data –
some issues to resolve in data format Will process tapes from Jan 2008 forward
• F17 will be processed when available from RSS Set up to acquire F17 from CLASS same source
for both NRT and RSS Tbs
Final processing for sea ice products
• Working with Comiso, Cavalieri, Parkinson,Markus F15 will be a “bridge” between F13 and F17 F17 data stream started on 26 March 2008 F17 same orbit as F13, operational successor to F13 F16 different orbit, (calibration issues?) – better to go
directly to F17 Final brightness temperature will be F13 to F17, with
F15 filling in gaps and bridging any necessaryoverlap
• F13 still operating but with gaps – may beenough to do direct intercalibration with F17without using F15; now 6+ months of overlap
And now for something completelydifferent…
Arctic Sea Ice News & Analysis
Arctic Sea Ice News & Analysis
• After success of past few years, communitynow expects NSIDC to produce an analysis
• Support for NSIDC summer sea ice analysis Previous done ad hoc through DAAC, spare time In 2008, some direct funding from NASA (thanks
Seelye!) Rest of funding through DAAC
• Expand to monthly reports year-round inaddition to more intensive summer reports(every 1-2 weeks)
• Direct NASA support for science analysis Scientists to analyze data and write analyses
o Serreze, Stroeve, Scambos, and Meier Programmer to analyze data, create images
o Matt Savoie• DAAC support for analysis
Public affairs office – media requestso Stephanie Renfrow and Katherine Leitzell
User services – user requestso Donna Scott and others
Operations – routine data processingo Peter Gibbons and Jonathan Kovarik
High demand for PAO and USO support
Arctic Sea Ice News & Analysis
Direct NASA supported “blog” activities
• Expanded to do monthly reports through theyear instead of summer Still have more intensive reporting schedule during
summer melt season (every 1-2 weeks)• Improved imagery
Shapefile contours (cleaner imagery) NASA Blue Marble
• More analysis, science information for FAQ• Outside scientists as “guest commentators”:
D. Perovich, J. Francis, M. Steele, J. Kay, T.Arbetter (NIC)
Improvements inspired by analysis site
• Redesign of Sea Ice Index (near completion) Near completion Cleaner design Formal documentation NASA Blue Marble option for daily images
• FAQ development• Other imagery
AMSR-E and SSM/I animations on GoogleEarth MODIS imagery – mosaics, projected on GE
Impact of analysis site – science community
• Improved visibility for NASA DAACdatasets and NSIDC
• Bringing together science community tocontribute content – a way to shareinformation in near real time
• Many positive comments from scientist• Source data for ARCUS Sea Ice
Outlook (NSF – J. Overland, H. Eicken)
Impact of analysis site – NSIDC web site
• Since April 7 debut, #1 site for nsidc.org,nearly 200,000 hits by August 21
• #1 NSIDC landing site – 16% of all entries tonsidc.org came through blog site
• 11% of total nsidc.org site traffic• Top 5 analysis pages: (1) home, (2) 2008
archive, (3) “About the Data”, (4) 2007archive, (5) FAQ
Impact of analysis site – data and user statistics
• Aug/Sep 2008 relative to 2007 300% increase for Sea Ice Index
(DAAC/NOAA) 45% increase for Goddard NASA Team 118% increase for NRT NASA Team
• Numerous (hundreds) of user requests,media request
• A lot of attention from skeptics
Miscellanea - A Couple of Other Issues
• Bootstrap algorithm code has beenprovided to NSIDC Can implement consistent processing in-
house and streamline Bootstrap products(as has been done with NASA Team)
Hopefully in the next few months• NSIDC on JAXA GCOM-W science
team (AMSR2) First meeting January 2009 – not clear how
many of science team will be funded toattend