1. Towards Understanding and Resolving Cross-Platform Biases in MICROS
Update since
Towards Understanding and Resolving Cross-Platform Biases in MICROS
Xingming Liang1,2 and Sasha Ignatov1
1NOAA/NESDIS/STAR, 2CSU/CIRA
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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2. Acknowledgments
Advanced Clear-Sky Processor for Oceans (ACSPO; NESDIS SST System): Sensor Radiances over Oceans with Clear-Sky Mask and QC
J. Sapper, Y. Kihai, B. Petrenko, J. Stroup, P. Dash, F. Xu, M. Bouali, X. Zhou – NESDIS SST Team
Community Radiative Transfer Model (CRTM) implemented in ACSPO
F. Weng, Y. Chen, P. Van Delst, Q. Liu, D. Groff, E. Borbas, C. Mueller – CRTM Team
AVHRR, MODIS, VIIRS Characterization & Cross-platform Consistency, including Double Differences (DD) for Global Space-based Inter-Calibration System (GSICS)
T. Chang, F. Wu, F. Yu, L. Wang, F. Weng, C. Cao, M. Goldberg, T. Hewison, X. Hu– GSICS Team
A. Wu, J. Xiong– MODIS Calibration Support Team (MCST)
Simon Hook – NASA/JPL
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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3. Cross-platform consistency between AVHRR, MODIS and VIIRS in MICROS
(Presented on by K. Saha)
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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4. Nighttime DD’s @3.7 µm (Ref=Metop-A GAC)
VIIRS recalibration
CRTM V2.1 implemented
N16: unstable and out of family
All AVHRRs, Terra/MODIS, and NPP/VIIRS are consistent to within ±0.1K
VIIRS Cal Change 7 Mar 2012 reset by +0.14K; Remains in-family
Terra was in AVHRR/VIIRS family, but Aqua was biased by ~0.3 K when CRTM V2.02 used Shifted by and K, respectively, after CRTM V2.1 was implemented on Sep. 13, 2012.
Metop-A and –B inconsistent by ~0.17 K, in part due to suboptimal CRTM coefficients in CRTM V2.1
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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5. Nighttime DD’s @11 µm (Ref=Metop-A GAC)
CRTM V2.1 implemented
N16: unstable and out of family
VIIRS recalibration
Metop-B: out of family
All AVHRRs and NPP/VIIRS are consistent to within ±0.1K
VIIRS Cal change 7 Mar 2012 reset by +0.14K – now better in family
Terra and Aqua/MODIS out of family by 0.6K – due to suboptimal CRTM coefficients in V Both are now back in family after CRTM V2.1 implemented on Sep. 13, 2012
Metop-A and -B are inconsistent by ~0.3 K, due to suboptimal coefficients used in CRTM V2.1
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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6. Nighttime DD’s @12 µm (Ref=Metop-A GAC)
CRTM V2.1 implemented
VIIRS recalibration
N16: unstable and out of family
All AVHRRs and NPP/VIIRS are consistent to within ±0.1K
VIIRS Cal Change 7 Mar 2012 reset +0.14K – now better in family
Terra and Aqua/MODIS out of family by 0.3K – due to suboptimal CRTM coefficients in V Both are now back in family after CRTM V2.1 implemented on Sep. 13, 2012
Metop-A and –B are consistent to within 0.04 K
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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7. Nighttime DD’s SST (Ref=Metop-A GAC)
CRTM V2.1 implemented
New SST Reg. Coeff. used
VIIRS recalibration
N16: unstable and out of family
All AVHRRs, MODISs and NPP/VIIRS SSTs are consistent to within ±0.1K
VIIRS Cal Change 7 Mar 2012: SST +0.10K – Out of family
New SST coefficients implemented 3 May 2012: SST -0.15K – Back in family
CRTM update resulted regression SSTs more noise, and the new coefficients have been implemented since Dec More data is needed to understand their performance.
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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8. Content – Progress since GSICS2013
Sensitivity analysis of effect of consistent CRTM coefficient on MICROS double differences (cf, Poster )
4 data sets used: ODAS-ORD, ODPS-ORD, ODAS-PW, ODPS-PW
3 metrics: M-O mean bias, STDs, and DDs
Preliminary result of cross-platform consistency between Metop-A and –B using newest CRTM coefficients
Meeting with MCST on cross-platform inconsistency between MODIS Terra and Aqua in IR37
Conclusion and future work
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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9. Sensitivity Analysis: Effect of Consistent CRTM coefficient on M-O Biases and DDs in MICROS (Example for IR37 shown here, Other bands and SST showed in Liang et al. Poster)
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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10. CRTM Coefficients Analyzed in MICROS
4 consistent CRTM Coefficients datasets were provided by Yong Chen and analyzed in MICROS using 1 day of global data (15 Jan 2013):
ODAS-ORD, ODAS-PW, ODPS-ORD, and ODPS- PW (Y. Chen et al., 2010&2011)
Based on the same baseline LBLRTM v11.7
All include CFC absorption
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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11. Methodology Compare 4 different results using the following metrics
Global M-O biases. M-O biases are expected to be (1) closer to zero and (2) coherent across bands (in particular, IR11 & IR12).
Global STDs of M-O biases. STDs are expected to be smaller.
Double differences for pairs of platforms in close orbits. For Hi-Res, (1) Metop-A and -B, and (2) NPP and Aqua. For GAC, (1) Metop-A and -B and (2) NOAA-18 and -19. DDs are expected to be fairly insensitive to CRTM formulation, as long as it is consistent. However, for better coefficients, DDs may be slightly smaller and more consistent across different pairs.
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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12. CRTM Coefficients in MICROS
AVHRR GAC (IR37)
Δ1 = N18 minus N19
Δ2 = M-A minus M-B
σ >>
IR37, ODAS_ORD
IR37, ODPS_ORD
Δ1= K
Δ1= K
Δ2= K
Δ2= K
σ >
σ >
σ >>
IR37, ODAS_PW
IR37, ODPS_PW
Δ1= K
Δ1= K
Δ2= K
Δ2= K
3/15/2013
CRTM Coefficients in MICROS
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13. CRTM Coefficients in MICROS
Hi-Res Sensors (IR37)
Δ1 = Aqua minus S-NPP
Δ2 = M-A minus M-B
σ ~
IR37, ODAS_ORD
IR37, ODPS_ORD
Δ1= K
Δ1= K
Δ2= K
Δ2= K
σ >
σ >
σ ~
IR37, ODAS_PW
IR37, ODPS_PW
Δ1= K
Δ1= K
Δ2= K
Δ2= K
3/15/2013
CRTM Coefficients in MICROS
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14. Observations in IR37 M-O biases STDs DDs
PW biases smaller than ORD by ~-0.06 K (except for VIIRS, where it’s larger by ~+0.05 K – check VIIRS ORD/PW coefficients???)
ODPS vs. ODAS: Biases are within ~±( )K of each other - no clear pattern. However, ODPS removes the large N16 anomaly ~1K seen in ODAS
PW-ODPS provides most favorable M-O biases. Need resolve VIIRS & N16 anomalies
STDs
ODPS STDs much smaller for all AVHRR GACs. Hi-res sensors are only minimally affected
PW STDs are slightly but consistently smaller than ORD STDs
PW-ODPS combination provides smallest STDs
DDs
Insensitive to ORD-PW, ODAS-ODPS to within ±0.01K, except Aqua/MODIS and VIIRS, where PW DDs are smaller than ORD by 0.08K. (related to VIIRS M-O ORD Bias).
Aqua PW is warmer than VIIRS by +0.14K and Aqua ORD is warmer by +0.24K. Both Metop-B ORD and PW are colder than Metop-A by 0.10K.
Before large PW-ORD differences are resolved, PW is recommended
Recommended Coefficients and Remaining Questions
PW-ODPS combinations seems to be the best choice in Ch3B
Q1 (CRTM): Anomalies in VIIRS and N16 PW-ODAS biases
Q2 (CAL/RSR): (Aqua-NPP) DD=+0.14K and (M-B - M-A) DD=-0.10K - real sensor biases
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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15. Preliminary Result: Cross-platform consistency between Metop-A and –B using consistent CRTM coefficients
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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16. MICROS “Official” (ODAS)
MB-MA = -0.16K
MB-MA = -0.32K
MB-MA = +0.04K
Metop-B minus Metop-A cross-platform biases are -0.16K in IR37, K in IR11, and +0.04K in IR12
Inconsistencies between AVHRR, Terra/MODIS and VIIRS are all within 0.1 K
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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17. Newest CRTM Coefficients
(ODPS_PW)
MB-MA = -0.10K
MB-MA = +0.00K
MB-MA = +0.23K
Cross-platform biases reduced to 0.1 K for IR37.
IR11: exemplarily consistency (cross-platform biases: ~0.002K).
IR12: K cross-platform biases. (appears to be Metop-B CAL issue, working with Tim Chang to resolve)
Inconsistencies between AVHRR and MODIS/VIIRS are now ~0.4 K
– need to understand the cause
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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18. Meeting held with MCST on 28 March 2013 towards resolving cross-platform inconsistency of ~0.3K between MODIS Terra and Aqua in IR37
Agree that cross-platform biases between MODIS Terra and Aqua in IR37 is due to MODIS CAL or RSR issue
A joint effort between MCST and SST Teams is underway towards resolving the anomaly
MCST will update Aqua RSRs and test in improved CAL
Will also send to SST team for testing
SST team will test in MICROS and feedback to MCST
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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19. Conclusions
DDs are employed to evaluate sensor radiances for radiometric stability and consistency, for GSICS quantitative applications
All newly added sensors (2 MODIS, VIIRS, Metop-B AVHRR) are stable from Jan ‘12 – pr
AVHRRs, MODISs and VIIRS BTs are consistent to within ±0.1K
There are three exceptions: NOAA-16 (unstable), Metop-B and Aqua (stable but biased)
VIIRS BTs remains closer in-family, following CAL update on 7 March 2012
Consistent CRTM Coefficients are critically important to understand and minimize model effect on MICROS DD
PW-ODPS combinations provides most favorable M-O biases and smallest STDs
In IR37, Aqua minus SNPP=+0.14K and M-B - M-A = -0.10K are real sensor biases
Preliminary result using newest coefficients shows cross-platform biases Metop-B minus Metop-A were improved in IR37 and IR11, but worsened in IR12
IR37: reduced to -0.1 K
IR11: now show exemplarily consistency
IR12: K cross-platform biases. (working with T. Chang to resolve)
Working with MCST
Cross- biases between MODIS Terra and Aqua in IR37 is likely due to CAL/RSR issue
A joint effort between MCST and SST Teams is underway to resolve
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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20. Thank you!
GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD
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