Towards Understanding and Resolving Cross-Platform Biases in MICROS Update since GSICS2013@Williamsburg Towards Understanding and Resolving Cross-Platform Biases in MICROS www.star.nesdis.noaa.gov/sod/sst/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 Slide 1 of 20

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 Slide 2 of 20

Cross-platform consistency between AVHRR, MODIS and VIIRS in MICROS (Presented on GSICS2013@Williamsburg by K. Saha) GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD Slide 3 of 20

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 BT@M12 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 +0.06 and +0.09 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 Slide 4 of 20

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 BT@M15 by +0.14K – now better in family Terra and Aqua/MODIS out of family by 0.6K – due to suboptimal CRTM coefficients in V2.02. 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 Slide 5 of 20

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 BT@M16 +0.14K – now better in family Terra and Aqua/MODIS out of family by 0.3K – due to suboptimal CRTM coefficients in V2.02. 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 Slide 6 of 20

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. 2012. More data is needed to understand their performance. GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD Slide 7 of 20

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 Slide 8 of 20

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 Slide 9 of 20

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 Slide 10 of 20

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 Slide 11 of 20

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=+0.133 K Δ1=+0.113 K Δ2=+0.082 K Δ2=+0.080 K σ > σ > σ >> IR37, ODAS_PW IR37, ODPS_PW Δ1=+0.127 K Δ1=+0.111 K Δ2=+0.101 K Δ2=+0.093 K 3/15/2013 CRTM Coefficients in MICROS Slide 12 of 20

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=+0.237 K Δ1=+0.223 K Δ2=+0.085 K Δ2=+0.086 K σ > σ > σ ~ IR37, ODAS_PW IR37, ODPS_PW Δ1=+0.155 K Δ1=+0.141 K Δ2=+0.105 K Δ2=+0.099 K 3/15/2013 CRTM Coefficients in MICROS Slide 13 of 20

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 ~±(0.01..0.03)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 Slide 14 of 20

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 Slide 15 of 20

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, -0.32 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 Slide 16 of 20

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: +0.23 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 Slide 17 of 20

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 Slide 18 of 20

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: +0.23 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 Slide 19 of 20

Thank you! GSICS Workshop/NOAA Satellite Conference, April 8-12, 2013, NCWCP, College Park, MD Slide 20 of 20