validation of the tmr and jmr wet path delay measurements using gps, ssm/i, and tmi
DESCRIPTION
Validation of the TMR and JMR Wet Path delay Measurements using GPS, SSM/I, and TMI. Shailen Desai Shannon Brown Bruce Haines Wenwen Lu Victor Zlotnicki Jet Propulsion Laboratory, California Institute of Technology. Ocean Surface Topography Science Working Team Meeting, March 14, 2007. - PowerPoint PPT PresentationTRANSCRIPT
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Validation of the TMR and JMR Wet Path delay Measurements using GPS, SSM/I, and TMI
Shailen DesaiShannon Brown
Bruce HainesWenwen Lu
Victor ZlotnickiJet Propulsion Laboratory, California Institute of Technology
Ocean Surface Topography Science Working Team Meeting, March 14, 2007
![Page 2: Validation of the TMR and JMR Wet Path delay Measurements using GPS, SSM/I, and TMI](https://reader036.vdocument.in/reader036/viewer/2022062815/56813019550346895d9592c7/html5/thumbnails/2.jpg)
March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 2
Objective
• Independent validation of wet path delay (WPD) measurements from Topex and Jason microwave radiometers.– SSM/I
• Special Sensor Microwave Imager on Defense Meteorological Satellite Program (DMSP) satellites.
• Available for duration of Topex/Poseidon and Jason-1 missions.– TMI
• Tropical Rainfall Measuring Mission’s Microwave Imager.• Available 1998-present (T/P cycle 193 onwards).
– Coastal GPS sites• 1-87 sites available for Topex/Poseidon (presently on original ground track only).• ~30 of 87 sites available for each cycle of Jason-1 mission.
• Characterize:– Temporal stability– Scale errors– Geographically correlated errors
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 3
Validation of TMRMGDRB and Replacement Product
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-9-6
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3
69
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0 40 80 120 160 200 240 280 320 360 400 440 480
TMR(MGDRB)-GPSTMR(MGDRB)-SSMITMR(MGDRB)-TMI
Topex Repeat Cycle
TMR from MGDRB
• TMR from MGDRB• 0.8 mm/yr drift from cycle
30-240• ~5mm peak-to-peak
dependence on satellite attitude regime (yaw state).
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-9-6
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3
69
1215
0 40 80 120 160 200 240 280 320 360 400 440 480
TMR (RP) - GPSTMR (RP) - SSMITMR (RP) - TMI
Topex Repeat Cycle
TMR from Replacement Product (RP)
• TMR Replacement Product
– Released Dec 13, 2006.
• Drift removed (< 0.05 mm/yr)
• Yaw state dependence reduced to < 1 mm.
• TMR RP is drier than TMR-MGDRB by ~ 3 mm.
• TMR-GPS is biased ~-9 mm from TMR-SSMI and TMR-TMI.
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 4
Daily Averages of TMR vs. SSMI and TMI
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5
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800 1600 2400 3200 4000 4800
TMR(MGDRB)-SSMITMR(MGDRB)-TMI
Days Since Jan 1, 1992
TMR from MGDRB
• TMR from MGDRB• Systematic yaw state errors
distinct in daily averages.
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-10
-5
0
5
10
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800 1600 2400 3200 4000 4800
TMR (Recal.) - SSMITMR (Recal.) - TMI
Days Since Jan 1, 1992
TMR from Replacement Product
• TMR from Replacement Product
• Yaw state errors removed.
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 5
Validation of JMRVersion B and Ongoing Recalibration
• JMR from GDRB• All 4 comparisons agree to
within 3.2 mm.• Residual (< 3mm) yaw state
dependence may remain after cycle 100.
• JMR-ECMWF has a drift of -0.3 mm/year.
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0 20 40 60 80 100 120 140 160 180 200
JMR (GDRB) - GPSJMR (GDRB) - SSMIJMR (GDRB) - TMIJMR (GDRB) - ECMWF
Jason Repeat Cycle
JMR from GDRB
• Recalibration of JMR – In preparation for Version C
GDRs.• Will be ~3mm drier than
version B GDRs.– Scale error corrected.
• JMR-ECMWF drift reduced to -0.25 mm/yr
– May have contribution from < 2 mm shifts after cycle 136 and 179 safeholds.
– Will be corrected in Version C.
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0 20 40 60 80 100 120 140 160 180 200
JMR (Recal.) - GPSJMR (Recal.) - SSMIJMR (Recal.) - TMIJMR (Recal.) - ECMWF
Jason Repeat Cycle
JMR from Recalibration
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 6
Scatter of JMR versus ECMWFJMR from GDRB JMR from Ongoing Recalibration
• Comparison to ECMWF suggests scale error of ~2% in JMR from Version B GDR.– Error consistent with known changes to pre-launch calbration coefficients.– Can be corrected by dividing JMR(GDRB) by 1.023
• JMR on version C GDRs will correct this error.
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 7
TMR versus JMR(Temporal Stability)
• Attitude dependence evident in TMR (MGDRB).
• Removed in TMR (RP).• TMR (RP) and JMR(Recal.)
drier than TMR (MGDRB) and JMR(GDRB) by ~3 mm.
– Effect of correcting scale error.
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-4
-2
0
2
4
6
342 344 346 348 350 352 354 356 358 360 362 364 366
TMR(MGDRB)-JMR(GDRB)TMR(RP)-JMR(GDRB)TMR(RP)-JMR(Recal.)
Topex Repeat Cycle
Cycle Averages
• Temporal variation of standard deviations of recalibrated TMR and JMR very consistent at 3 mm.
– Random noise ~ 2mm.
0
1
2
3
4
5
342 344 346 348 350 352 354 356 358 360 362 364 366
TMR(MGDRB)-JMR(GDRB)TMR(RP)-JMR(GDRB)TMR(RP)-JMR(Recal.)
Topex Repeat Cycle
Cycle Standard Deviations
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 8
Scatter of TMR vs JMR (GDRB)TMR(MGDRB) vs JMR(GDRB) TMR(RP) vs JMR(GDRB)
• Significant reduction of outliers in TMR-JMR differences from recalibration and reprocessing of TMR.
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 9
TMR versus JMRGeographically Correlated Differences
• As previously shown, banding around continents in TMR-JMR differences.
– Differences with island and continental GPS sites suggested TMR as source.
• Still present in recalibrated TMR and JMR.
– < 1 mm effect from 200 km out to open ocean.
– -3.5 mm from 200 to 50 km.
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0 50 100 150 200 250 300 350 400 450 500 550 600 650
TMR(MGDRB)-JMR(GDRB)TMR(RP)-JMR(GDRB)TMR(RP)-JMR(Recal.)
Distance from Land (km)
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 10
Average of Differences w.r.t. Independent Measurements
TMR (RP) JMR (GDRB) JMR (Recal.)
SSMITMIGlobal GPSContin. GPSIsland GPS
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-5
0
5
10
TMR (MGDRB)
Average of Wet Path Delay Differences (mm)
• JMR comparisons to SSMI, TMI, and GPS statistically identical.• TMR comparisons to GPS are biased by ~ -9 mm versus SSMI and TMI.• Separation of GPS comparisons by island and continental sites shows large
discrepancy for TMR, but not for JMR.• TMR likely dominant source for errors near continents.
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 11
Summary
• TMR recalibrated and reprocessed.– Provided as TMR Replacement Product (Dec. 13, 2006)– Provided on Topex Retracked GDRs.– Drift and yaw state effects corrected.– Coastal effect remains.
• ~3.5 mm wetter as approaching coast from 200 km out.
• JMR (GDRB) corrects large shifts observed in version A GDRs.– < 2mm shifts may be present after cycle 136 and 179 safeholds.
• Will be corrected in Version C GDRs.– Scale error of ~2% present in JMR (GDRB)
• Will be corrected in Version C GDRs.• Can be corrected by dividing JMR(GDRB) by 1.023.
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BACKUP SLIDES
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 13
Senatosa
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Distance from Land (km)
TMR-JMR Wet Path Delay (mm)
Time to Senatosa (sec)
TMR wetter orJMR drier betweenland masses.
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 14
Scatter of TMR(RP) vs JMR
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March 14, 2007 Ocean Surface Topography Science Working Team MeetingCal/Val Splinter Session
SD/SB/BH/WL/VZ - 15
Mean Offsets w.r.t. Independent Measurements
Radiometer SSMI TMI Global GPS
IslandGPS
Continental GPS
TMR(MGDRB) 2.4 4.3 -5.8 -0.4 -8.2
TMR (RP) 6.0 7.7 -2.4 1.8 -4.4
JMR(GDRB) 3.2 2.6 1.7 -1.8 1.1
JMR(Recal.) 5.6 6.7 4.2 1.0 3.3
• JMR comparisons to SSMI, TMI, and GPS statistically identical.• TMR comparisons to GPS are biased by ~ -9 mm versus SSMI and TMI.• Separation of comparisons to island and continental GPS shows large discrepancy
for TMR, but not for JMR.• TMR likely dominant source for ~4 mm errors near continents.