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NOAA produces operational sea surface temperature (SST) data products from two VIIRS sensors, flown onboard NPP (launched in Oct 2011) and NOAA-20 (N20, aka. JPSS-1 prior to launch; launched in Nov 2017). These first two satellites in the US new generation Joint Polar Satellite System (JPSS) series will be followed by JPSS-2 to -4, planned for launch in 2022, 2026, and 2031, respectively. The goal of VIIRS SST Reanalyses (RANs) is to generate stable, accurate and consistent data products, which currently include Level 2P (L2P; swath projection; 26 Gb/day) and gridded 0.02° L3U (0.45 Gb/day). The RAN comprises multiples steps, including 1) RDR-to-SDR conversion, i.e., reprocessing of all available VIIRS L0 (“Raw Data Records”, RDRs) into improved L1b (“Sensor Data Records”, SDRs), using latest and most accurate sensor calibration, 2) pre-processing, which includes destriping the radiances, resampling VIIRS imagery (to minimize the effect of bow-tie deletions and distortions), and aggregating original 86-sec granules into 10-min SDR granules; 3) feeding those into the latest NOAA Advanced Clear-Sky Processor for Oceans (ACSPO) enterprise SST code (currently, version 2.61), and producing L2P; 4) gridding L2P data and producing L3U; 5) matching L2P/3U data with several accurate Level 4 (L4) analyses, and with quality controlled in situ SSTs from the NOAA in situ SST Quality Monitor, iQuam, system; 6) calculation of the corresponding performance statistics – global daily mean biases and standard deviations, SDs, of various paired SST differences, ΔTs, stratified by day and night, and displaying them in the NOAA SST Quality Monitor (SQUAM) web-based system; 6) generation of SST imagery over ~30 regional targets and routine monitoring in another NOAA system, ACSPO Regional Monitor for SST (ARMS); 7) calculation of brightness temperature (BT) differences between measured BTs and those simulated using the fast Community Radiative Transfer Model (CRTM), as a part of ACSPO L2P processing, and displaying in another NOAA web-based system, MICROS; 8) product archival at NOAA (CoastWatch and NCEI) and at NASA/JPL PO.DAAC. NPP RAN1, performed in late 2015 jointly with UW/CIMSS using ACSPO v2.40, covered a period from Mar’2012-Dec’2015. The data from Jan’2016 – on have been supplemented from operational ACSPO products with various versions (2.41, 2.60, and 2.61). Some issues, unresolved in RAN1, are now being addressed in RAN2. The most important features of RAN2 include the addition of N20 data; fixing quarterly spikes in SST time series (resulting from the VIIRS black-body warm-ups/cool-downs, WUCDs); and using a consistent ACSPO version 2.61 for the full NPP and N20 records. As of this writing, 64 months of NPP (Jan 2014 – Apr 2019) and 16 months of N20 (Jan 2018 – Apr 2019) RAN2 data have been generated. The remaining two years of NPP data (Feb 2012 – Dec 2013), are being processed. The SST records appear stable, and consistent with in situ data and across NPP/N20. The RAN2 data are currently being archived at the NASA/JPL PO.DAAC, and NOAA CoastWatch and NCEI archives.
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