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Effect of consistent CRTM coefficients on M-O bias and DDs in MICROS

Effect of consistent CRTM coefficients on M-O bias and DDs in MICROS. Xingming Liang and Alexander Ignatov. Motivation. Cross-platform inconsistencies are at least in part due to inconsistent CRTM coefficients for different sensors/platforms

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Effect of consistent CRTM coefficients on M-O bias and DDs in MICROS

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  1. Effect of consistent CRTM coefficients on M-O bias and DDs in MICROS Xingming Liang and Alexander Ignatov CRTM Coefficients in MICROS

  2. Motivation • Cross-platform inconsistencies are at least in part due to inconsistent CRTM coefficients for different sensors/platforms • Sensitivity analysis of CRTM Coefficients is critically important for understanding and minimizing model effect on MICROS double differences MODIS CRTM Coefficients Recalculated Metop-B CRTM Coefficients: Calculated Correctly? from www.star.nesdis.noaa.gov/sod/sst/micros CRTM Coefficients in MICROS

  3. 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 • Based on the same baseline LBLRTM v11.7 • All include CFC absorption CRTM Coefficients in MICROS

  4. 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. CRTM Coefficients in MICROS

  5. 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 CRTM Coefficients in MICROS

  6. Δ1 = Aqua minus S-NPP Hi-Res Sensors (IR37) 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 CRTM Coefficients in MICROS

  7. Observations in IR37 • M-O biases • 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 is warmer than VIIRS by +0.14K. Metop-B is 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 CRTM Coefficients in MICROS

  8. AVHRR GAC (IR11) Δ1 = N18 minus N19 Δ2 = M-A minus M-B σ > IR37, ODAS_ORD IR37, ODPS_ORD Δ1=+0.077 K Δ1=+0.074 K Δ2=+0.000 K Δ2=-0.003 K σ ~ σ ~ σ > IR37, ODAS_PW IR37, ODPS_PW Δ1=+0.071 K Δ1=+0.076 K Δ2=+0.013 K Δ2=-0.007 K CRTM Coefficients in MICROS

  9. Δ1 = Aqua minus S-NPP High Resolution Sensors (IR11) Δ2 = M-A minus M-B σ > IR37, ODAS_ORD IR37, ODPS_ORD Δ1=+0.052 K Δ1=+0.015 K Δ2=+0.005 K Δ2=0.000 K σ ~ σ ~ σ > IR37, ODAS_PW IR37, ODPS_PW Δ1=+0.006 K Δ1=+0.047 K Δ2=+0.017 K Δ2=-0.002 K CRTM Coefficients in MICROS

  10. Observation in IR11 • M-O biases • PW biases comparable with ORD to within ~±0.01K – no clear advantage • ODPS Biases larger than ODAS by ~+0.03K (AVHRR), +0.045K (VIIRS), +0.085K (MODIS) • Large difference between (MODIS-VIIRS) and (AVHRR) sensors up to 0.4K – need resolve • IR11 and IR12 are more consistent for ODPS than for ODAS • ODPS in combination with (either PW or ORD) seems favorable for M-O biases • STDs • ODPS STDs slightly but consistently smaller. PW STDs are comparable with ORD STDs • ODPS in combination with (either PW or ORD) provides smaller STDs • DDs • Insensitive to ORD-PW, ODAS-ODPS to within ±0.01K, except for Aqua/MODIS and VIIRS, where ODAS DDs are smaller than ODPS by 0.04K. This difference should be understood • IF ODPS is used, then Aqua is warmer than VIIRS by +0.05K. M-B is consistent with M-A • Recommended Coefficients and Remaining Questions • PW-ODPS is recommended (ODPS has smaller STDs, and PW for consistency with Ch3B) • Q1 (CRTM): Deltas between MODIS/VIIRS & AVHRR M-O biases ~0.4K – caused by CFC? In official MICROS, deltas between AVHRR and MODIS/VIIRS do not exceed 0.1K. • Q2 (CRTM): Deltas between ODAS-ODPS M-O biases and (likely related) deltas in DDs? • Q3 (CAL): (Aqua-NPP) DD=+0.05K bias in IR11 CRTM Coefficients in MICROS

  11. AVHRR GAC (IR12) Δ1 = N18 minus N19 Δ2 = M-A minus M-B σ > IR12, ODAS_ORD IR12, ODPS_ORD Δ1=+0.020 K Δ1=+0.010 K Δ2=-0.227 K Δ2=-0.241 K σ ~ σ ~ σ > IR12, ODPS_PW IR12, ODAS_PW Δ1=+0.015 K Δ1=+0.003 K Δ2=-0.239 K Δ2=-0.226 K CRTM Coefficients in MICROS

  12. Δ1 = Aqua minus S-NPP High Resolution Sensors (IR12) Δ2 = M-A minus M-B σ > IR12, ODPS_ORD IR12, ODAS_ORD Δ1=+0.060 K Δ1=+0.071 K Δ2=-0.237 K Δ2=-0.225 K σ ~ σ ~ σ > IR12, ODPS_PW IR12, ODAS_PW Δ1=+0.067 K Δ1=+0.079 K Δ2=-0.234 K Δ2=-0.223 K CRTM Coefficients in MICROS

  13. Observation in IR12 • M-O biases • PW biases are generally slightly but consistently smaller than ORD by ~0.01-0.02K • ODPS Biases larger than ODAS by ~+0.03±0.01K (AVHRR, VIIRS, MODIS) • Large difference between (MODIS-VIIRS) and (AVHRR) up to 0.4K seen in IR11 not there • IR11 and IR12 are more consistent for ODPS than for ODAS • ODPS in combination with (either PW or ORD) seems favorable for M-O biases • STDs • ODPS STDs slightly but consistently smaller. PW STDs are comparable with ORD STDs • ODPS in combination with (either PW or ORD) provides smaller STDs • DDs • Insensitive to ORD-PW, ODAS-ODPS to within ±0.01K, for all sensors • Aqua is warmer than VIIRS by +0.07K. M-B warmer than M-A by 0.23K • Recommended Coefficients and Remaining Questions • PW-ODPS is recommended (ODPS has smaller STDs; PW for consistency with Ch3B) • Q1 (CAL): (Aqua-NPP) DD=+0.07K; (M-B – M-A) DD=0.23K – needs reconciliation CRTM Coefficients in MICROS

  14. Δ1 = N18 minus N19 AVHRR GAC (SST) Δ2 = M-A minus M-B σ ~ SST, ODAS_ORD SST, ODPS_ORD Δ1=-0.112 K Δ1=-0.111 K Δ2=+0.028 K Δ2=+0.028 K σ ~ σ ~ σ ~ SST, ODPS_PW SST, ODAS_PW Δ1=-0.111 K Δ1=-0.111 K Δ2=-0.028 K Δ2=+0.028 K CRTM Coefficients in MICROS

  15. Δ1 = Aqua minus S-NPP High Resolution Sensors (SST) Δ2 = M-A minus M-B σ ~ SST, ODAS_ORD SST, ODPS_ORD Δ1=+0.013 K Δ1=+0.014 K Δ2=+0.025 K Δ2=+0.024 K σ ~ σ ~ σ ~ SST, ODPS_PW SST, ODAS_PW Δ1=+0.013 K Δ1=+0.014 K Δ2=+0.025 K Δ2=-0.024 K CRTM Coefficients in MICROS

  16. Observation in SST • M-O mean biases, SDs and DDs are insensitive to the choice of ORD-PW, ODAS-ODPS for all platforms • The sample size (indirect effect through the cloud mask) is comparable for AVHRR GAC, but largest for PW-ODPS choice CRTM Coefficients in MICROS

  17. Conclusions • SDs are generally smaller in ODPS vs. ODAS, and in PW vs. ORD. • Overall, ODPS-PW is recommended for the use in model simulation. • N-16 ODAS has a large anomaly up to 1K, looks much better for ODPS. Understanding this issue is needed. • VIIRS PW M-O biases wrt. ORD are reversed in IR37 compared to all other platforms – this anomaly should be understood • Inconsistencies between AVHRR and MODIS&VIIRS are ~0.4 K in IR. Maybe related to CFS - in MICROS, the bias does not exceed 0.1K. Further analysis is needed. • Inconsistencies between Metop-B and -A are ~+0.23 K in IR12, and -0.10K in IR37. Joint work between SST team, CRTM team and STAR sensor calibration team is needed to resolve cross-platform biases. • Aqua is warmer than VIIRS: by +0.14K in IR37, +0.05K in IR11, and +0.07K in IR12. Need to work with VIIRS SDR and MCST to resolve • SSTs are not affected by CRTM coefficients directly, but affected indirectly through the cloud mask. The largest sample size is for PW-ODPS coefficients CRTM Coefficients in MICROS

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