ACSPO Global SST from VIIRS

These VIIRS SST data are produced using the NOAA Advanced Clear-Sky Processor for Ocean (ACSPO) SST system, from the afternoon NPP, N20 and N21 satellites, in two formats: L2P and L3U (uncollated). The data are reported in 10 min granule files in NetCDF4 format, compliant with the GHRSST Data Specifications v2 (GDS2). For each satelite, there are 144 granules per 24 hr interval, with a total data volume of ~7.1 GB/day for L2P, and ~0.4 GB/day for L3U.

    Data Access
    Metadata
    HTTPS
    THREDDS
    PO.DAAC Archive
    NCEI Archive
    Sample Filenames

    L2P: 20120301001000-OSPO-L2P_GHRSST-SSTsubskin-VIIRS_NPP-ACSPO_V2.80-v02.0-fv01.0.nc 
    L3U: 20120301001000-OSPO-L3U_GHRSST-SSTsubskin-VIIRS_NPP-ACSPO_V2.80-v02.0-fv01.0.nc

    Global map projection displaying a granule of SST data

    These VIIRS SST data are produced using the NOAA Advanced Clear-Sky Processor for Ocean (ACSPO) SST system, from the afternoon NPP and N20 satellites, in two formats: L2P and L3U (uncollated). The data are reported in 10 min granule files in NetCDF4 format, compliant with the GHRSST Data Specifications v2 (GDS2). There are 144 granules per 24 hour interval, with a total data volume of ~7 GB/day for L2P, and ~0.5 GB/day for L3U (per-sensor) .

    The L2P/L3U SST data is produced at NOAA STAR using the official enterprise ACSPO algorithms V2.80. A 2-week rotated buffer of the NRT data is provided here on Coast Watch, whereas the full data set is available from PO.DAAC and NOAA NCEI (see links under "Data Access"). Note that the NCEI archive has not been backfilled with ACSPO V2.80 and therefore contains SST data from earlier ACSPO versions, while PO.DAAC contains the full V2.80 archive. A complete archive of ACSPO V2.80 data is available on the Coast Watch archive for L3U data only due to large L2P data volume.

    ACSPO retrievals are made in full VIIRS swath (~3,000 km). For data assimilation applications (such as production of L4 analyses, especially those that blend satellite and in situ data), correction for the Sensor-Specific Error Statistics (SSES; reported in ACSPO files; Petrenko et al., 2016) biases is strongly recommended. The NOAA SST team worked with the NOAA calibration team and used an up-to-date converter from RDR (L0) to SDR (L1b), to address quarterly spikes in day-time SST bias which coincide with quarterly warm-up-cool-down calibration exercises onboard NPP/N20. The algorithms used in VIIRS reanalysis version 3 (RAN3) are documented in Jonasson et al., 2022.

    In each valid water pixel (defined as ocean, sea, lake or river, up to 5km inland; note that in "invalid" pixels, defined as those with >5km inland, fill values are reported), the following layers are reported in both L2P and L3U, among others: SSTs derived using multi-channel SST (MCSST; night) and Non-Linear SST (NLSST; day) algorithms (Petrenko et al., 2014); ACSPO clear-sky mask (ACSM; provided in each pixel as part of l2p_flags; Petrenko et al., 2010); SSES bias and standard deviation (Petrenko et al., 2016); GFS/MERRA wind speed; and ACSPO SST minus reference (Canadian Met Centre L4 SST).

    Only ACSM "confidently clear" pixels (equivalent to GDS2 "quality level"=5; QLs are also reported for each pixel) should be used. The ACSM also provides day/night, land, ice, twilight, and glint flags. Note that users of ACSPO data have the flexibility to ignore the ACSM, derive their own clear-sky mask, and use SSTs in those pixels.

    Both L2P and L3U SSTs are monitored and validated against in situ data (Xu and Ignatov, 2014) in SQUAM (Dash et al., 2010) and ARMS systems, and brightness temperatures are monitored in MICROS (Liang and Ignatov, 2011).

    Short Names
    L2P: ACSPO_VIIRS_L2P
    L3U: ACSPO_VIIRS_L3U
    Temporal Start Date
    February 1, 2012
    Temporal Coverage

    NRT NPP L2P/L3U: 1 Feb 2012 to present
    NRT N20 L2P/L3U: 5 Jan 2018 to present
    NRT N21 L2P/L3U: 19 March 2023 to present
    RAN NPP L2P/L3U: 1 Feb 2012 to present
    RAN N20 L2P/L3U: 5 Jan 2018 to present
    RAN N21 L2P/L3U: 19 March 2023 to present

    Product Families
    Sea Surface Temperature
    Measurements
    Sea Surface Temperature - Polar-orbiting
    Processing Levels
    Level 2
    Level 3
    Latency Groups
    0 Hours <= 24 Hours (NRT)
    24+ hours (Delayed)
    Latency Details

    NRT: <6 hours
    RAN: 8 weeks

    Spatial Resolution Groups
    100m < 2km
    2km+
    Spatial Resolution Details
    L2P: 0.75km @ Nadir; ~1.5km @ swath edge
    L3U: 0.02¬į
    Data Providers
    NOAA
    NESDIS
    STAR
    Spatial Coverage

    Global

    Description

    180W - 180E
    90N - 90S

    ACSPO

    Description

     Advanced Clear Sky Processor for Ocean (ACSPO) is the NOAA Enterprise SST system

    NOAA

    Description

    National Oceanic and Atmospheric Administration - 17 / 18 / 19 / 20 / 21

    Platform Type
    Low Earth Orbit Satellite (LEO)
    Instruments
    Organizations
    NASA
    NOAA
    Orbital Altitude
    834 km
    Equatorial Crossing Times
    13:25 asc

    SNPP

    Description

    Suomi National Polar-orbiting Partnership

    Platform Type
    Low Earth Orbit Satellite (LEO)
    Instruments
    Organizations
    NASA
    NOAA
    Orbital Altitude
    833 km
    Equatorial Crossing Times
    13:25 asc

    VIIRS

    Description

    Visible Infrared Imaging Radiometer Suite

    Platforms
    Instrument Types
    Imager
    Organizations
    NASA

    The ACSPO NPP/N20/N21 VIIRS RAN3 data set is provided by NOAA STAR. We strongly recommend contacting NOAA SST team led by A. Ignatov before the data are used for any publication or presentation.

    ** When you use our data, please reference the product citation (if available) and acknowledge "NOAA CoastWatch" **