SST – GSICS Connections 2012 GSICS Users’ Workshop 4 September 2012, Sopot, Poland SST – GSICS Connections Sasha Ignatov1, Xingming Liang1,2, Prasanjit Dash1,2 1NOAA/NESDIS and 2CSU/CIRA 4 September 2012 SST and GSICS

Conducts SST retrievals, leads community JPSS and GOES-R SST efforts NESDIS STAR SST Team Conducts SST retrievals, leads community JPSS and GOES-R SST efforts Part of the international Group for High Resolution SST (GHRSST; www.ghrsst.org) SST Quality Monitor, SQUAM www.star.nesdis.noaa.gov/sod/sst/squam/ Works with GSICS to link high-quality SSTs to clear-sky ocean radiances Monitoring IR Clear-sky Radiances over Oceans for SST (MICROS; www.star.nesdis.noaa.gov/sod/sst/micros/ Specific for nesdis 4 September 2012 SST and GSICS

SST – GSICS links SST is highly accurate/precise product used for Climate monitoring; Operational weather & ocean forecasting; Ecosystem assessment; Tourism; Fisheries; Forcing/Validating Ocean models; Military/Defense applications; etc SST in thermal IR is retrieved from clear-sky ocean radiances POES – AVHRR, MODIS, ATSR, VIIRS GEO – GOES, MSG/SEVIRI, MTSAT, GOES-R/ABI Two types of SST retrievals Regression: Need radiance stability of individual bands/sensors Physical (RTM-based): Need absolute accuracy GSICS-SST Links GSICS – Provide highly accurate and consistent radiances to SST SST – Derive accurate SST; Provide feedback to GSICS Specific for nesdis 4 September 2012 SST and GSICS

Nighttime Heritage NOAA minus Reynolds SST in SQUAM SSTs from different platforms are largely consistent, except N16, and to a lesser extent, N18 from 2011-on www.star.nesdis.noaa.gov/sod/sst/squam/ Median, Satellite SST - Reynolds In what follows, MICROS for the new NOAA retrieval system, ACSPO, is used from 2008-on to link SST with sensor radiances anomalies Specific for nesdis 4 September 2012 SST and GSICS

Nighttime ACSPO Regression – Reynolds SST in MICROS www.star.nesdis.noaa.gov/sod/sst/micros/ Note that SST anomalies in ACSPO are different from heritage This is because of different definition of day and night, and different cloud mask N16 shows larger deviations from family, but more regular than in heritage system This viewgraph shows direct differencing but, “double differences” can be used to minimize the effect of unstable reference 4 September 2012 SST and GSICS

SST Double Differences (“DD”) in MICROS Regression – Reynolds Biases Regression (ACSPO) = at night, MCSST (linear combination of 3.7, 11, and 12µm bands) Reynolds = Global daily 0.25° analysis Double Differences (“DD”) for SST Reynolds used as a “Transfer Standard” and cancels out, leaving “Reg1-Reg2” DDs cancel out/minimize systematic errors/instabilities in (Sat-Ref) arising from Errors/Instabilities in Reynolds SST Updates to SST or cloud masking ACSPO algorithms (simultaneously made for the two platforms being compared) Day and Night Data are monitored in MICROS. However, only night data are used for cross-platform consistency checks here, to minimize effects of diurnal variability 4 September 2012 SST and GSICS

Nighttime DD’s SST (Ref=Metop-A GAC) www.star.nesdis.noaa.gov/sod/sst/micros/ N17 (Equator Xing Time, EXT~10:30pm) consistent with Metop-A (EXT~9:30pm) N19 (EXT~1:30am) consistent with Metop-A and N17 N18 (EXT~1:30am) less consistent; and N16 (EXT~5am) most inconsistent 4 September 2012 SST and GSICS

BT Double Differences (“DD”) in MICROS Model minus Observation (“M-O”) Biases M (Model) = Community Radiative Transfer Model (CRTM) simulated TOA Brightness Temperatures (w/ Reynolds SST, GFS profiles as input) O (Observation) = Clear-Sky sensor (AVHRR, MODIS, VIIRS) BTs Double Differences (“DD”) for BTs “M” used as a “Transfer Standard” and cancels out, leaving “Obs1-Obs2” DDs cancel out/minimize systematic errors/instabilities in BTs arising from Errors/Instabilities in Reynolds SST & GFS Missing aerosol Possible systemic biases in CRTM Updates to ACSPO algorithm; etc Day and Night Data are monitored in MICROS. However, only night data are used for cross-platform consistency checks here, to minimize effects of diurnal variability and solar contamination 4 September 2012 SST and GSICS

Nighttime DD’s @3.7 µm (Ref=Metop-A GAC) www.star.nesdis.noaa.gov/sod/sst/micros/ Shape of BT DDs closely reproduces the shape of SST DDs Cross-platform biases reach several tenths of a Kelvin They cannot be explain by differences in the Equator Xing Time 4 September 2012 SST and GSICS

Nighttime DD’s @11 µm (Ref=Metop-A GAC) www.star.nesdis.noaa.gov/sod/sst/micros/ Systematic cross-platform biases are taken care of by Regression SST They can be also removed by “bias correction” in “physical” retrievals The most troublesome for SST are radiance instabilities SST needs help from GSICS, to flatten them out from “first principles” 4 September 2012 SST and GSICS

Nighttime DD’s @12 µm (Ref=Metop-A GAC) www.star.nesdis.noaa.gov/sod/sst/micros/ Shape of the biases is generally reproducible from band to band, suggesting that they are coming from sensor instabilities Several tenths of a Kelvin is a large error for SST and must be removed 4 September 2012 SST and GSICS

Adding NPP VIIRS and Terra/Aqua MODIS in MICROS NPP launched on 28 October 2012 Transition to Joint Polar Satellite System (JPSS) US: VIIRS instrument on PM platforms NPP (2011), J1 (~2016) and J2 (~2019) Europe: AVHRR instrument on AM platforms Metop-A (2006), - B (2012), and -C (2017) Links between AVHRR and VIIRS instruments must be established Cryoradiator doors opened on 18 January 2012 SST Team started processing global VIIRS data on 23 Jan 2012 VIIRS SSTs are monitored in SQUAM, and Clear-Sky Ocean Radiances monitored in MICROS MODIS Radiances and SSTs were added simultaneously Terra and Aqua SSTs were added in SQUAM, and Clear-Sky Ocean Radiances in MICROS, simultaneously with VIIRS on 23 Jan 2012 Specific for nesdis 4 September 2012 SST and GSICS

Nighttime DD’s @3.7 µm (Ref=Metop-A GAC) N16: unstable and out of family VIIRS recalibration Aqua: out of family by 0.3K All AVHRRs, Terra/MODIS, and NPP/VIIRS are consistent to within 0.15K VIIRS is in AVHRR family. Note Cal Change on 7 Mar 2012 (BT@M12: +0.14K) Aqua: out of family by -0.3K 4 September 2012 SST and GSICS

Nighttime DD’s @11 µm (Ref=Metop-A GAC) VIIRS recalibration N16: unstable and out of family Terra & Aqua: out of family by 0.6K All AVHRRs and NPP/VIIRS are consistent to within 0.15K VIIRS is in AVHRR family. Note Cal change on 7 Mar 2012 (BT@M15: +0.14K) Terra and Aqua/MODIS out of family by 0.6K. Reason is not sensor but suboptimal CRTM coefficients in CRTM V2.02. Working to fix. 4 September 2012 SST and GSICS

Nighttime DD’s @12 µm (Ref=Metop-A GAC) N16: unstable and out of family VIIRS recalibration Terra & Aqua: out of family by 0.3K All AVHRRs and NPP/VIIRS are consistent to within 0.15K VIIRS is in AVHRR family. Note Cal change on 7 Mar 2012 (BT@M16: +0.14K) Terra and Aqua/MODIS out of family by 0.3K. Reason is not sensor but suboptimal CRTM coefficients in CRTM V2.02. 4 September 2012 SST and GSICS

Nighttime DD’s SST (Ref=Metop-A GAC) New Reg. Coeff. used VIIRS recalibration Terra & Aqua SSTs are in family, due to use of empirical regression N16: unstable and out of family All AVHRRs, MODISs and NPP/VIIRS SSTs are consistent to within 0.15K VIIRS Cal Change on 7 Mar 2012: SST +0.10K – Out of family New SST coefficients implemented 3 May 2012: SST -0.15K – Back in family 4 September 2012 SST and GSICS

Summary MICROS monitors all on-orbit AVHRRs, 2 MODISs on Terra and Aqua, and NPP VIIRS Most sensors are stable and cross-platform consistent to within <±0.1K The remaining cross-platform systematic biases are easy to take care of by regression SST algorithm, or by empirical bias correction in physical retrievals Some sensors are unstable (AVHRRs on NOAA-16 and -18) - Those are most challenging for SST Two MODIS instruments are out of family. This is a combination of CRTM issues in bands 31/32 (11/12 µm) and sensor issues in band 20 (3.7 µm) Specific for nesdis 4 September 2012 SST and GSICS

Ongoing Work & Remaining Questions Consistent CRTM for various sensors: Critical for MICROS MODIS CRTM coefficients inconsistent with AVHRR/VIIRS – appears as sensor problem. In fact, it’s CRTM issue, work is underway to fix Terra & Aqua/MODIS inconsistent in band 20 (3.7µm) by 0.3K This appears to be real sensor calibration problem, and the largest “out-of-family” deviation so far. Working with Jack Xiong to resolve Q1: Are MICROS results consistent with imager trending? Against spectrometers (AIRS, IASI, CrIS)? Using Simultaneous Nadir Overpasses? Q2: If results are consistent, then we should work together to Stabilize the unstable sensors (N16, N18) Reconcile BTs form various SST sensors Do this from “first principles” (better understand sensors, improve cal procedures) rather than “empirical bias corrections” Specific for nesdis 4 September 2012 SST and GSICS