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