Coast Watch Holding: Near Real Time (~14 days to present)

Product Resource Locator
Level 2P (L2P)  
NPP/N20 L2P (data search) https://coastwatch.noaa.gov/cw_html/cw_polygon_search.html
NPP L2P (HTTPS) https://coastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/npp/l2p
N20 L2P (HTTPS) https://coastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/n20/l2p
NPP L2P (FTP) ftp://ftpcoastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/npp/l2p
N20 L2P (FTP) ftp://ftpcoastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/n20/l2p
NPP L2P (THREDDS) https://coastwatch.noaa.gov/thredds/catalog/swathNPPVIIRSNRTL2PWW00/catalog.html
N20 L2P (THREDDS) https://coastwatch.noaa.gov/thredds/catalog/swathN20VIIRSNRTL2PWW00/catalog.html
Level 3 Uncollated (L3U)  
NPP L3U (HTTPS) https://coastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/npp/l3u
N20 L3U (HTTPS) https://coastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/n20/l3u
NPP L3U (THREDDS) https://coastwatch.noaa.gov/thredds/catalog/gridNPPVIIRSNRTL3UWW00/catalog.html
N20 L3U (THREDDS) https://coastwatch.noaa.gov/thredds/catalog/gridN20VIIRSNRTL3UWW00/catalog.html
NPP L3U (FTP) ftp://ftpcoastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/npp/l3u
N20 L3U (FTP) ftp://ftpcoastwatch.noaa.gov/pub/socd2/coastwatch/sst/nrt/viirs/n20/l3u

Coast Watch Holding: Scientific quality 'Reanalysis' (RAN3)* data. New data is added in delayed mode (DM)*.

Product Resource Locator
NPP L3U (HTTPS) https://coastwatch.noaa.gov/pub/socd2/coastwatch/sst/ran/viirs/npp/l3u
N20 L3U (HTTPS) https://coastwatch.noaa.gov/pub/socd2/coastwatch/sst/ran/viirs/n20/l3u
NPP L3U (FTP) ftp://ftpcoastwatch.noaa.gov/pub/socd2/coastwatch/sst/ran/viirs/npp/l3u/
N20 L3U  (FTP) ftp://ftpcoastwatch.noaa.gov/pub/socd2/coastwatch/sst/ran/viirs/n20/l3u/
NPP L3U (THREDDS) https://coastwatch.noaa.gov/thredds/catalog/gridNPPVIIRSSCIENCEL3UWW00/catalog.html
N20 L3U (THREDDS) https://coastwatch.noaa.gov/thredds/catalog/gridN20VIIRSSCIENCEL3UWW00/catalog.html

PO.DAAC Archive: Reanalysis/reprocessed (RAN3)* data. New data is added in NRT* and overwritten by DM* data with a 8 week delay.

Product Resource Locator
NPP L2P 10.5067/GHVRS-2PO28
N20 L2P 10.5067/GHV20-2PO28
NPP L3U 10.5067/GHVRS-3UO28
N20 L3U 10.5067/GHV20-3UO28

NCEI Archive: Reanalysis/reprocessed (RAN2)* data. New data is added in NRT

Product Resource Locator
NPP L2P 10.7289/v5pr7sx5
N20 L2P 10.25921/sfs7-9688
NPP L3U 10.7289/v5kk98s8
N20 L3U 10.25921/7c1m-rw73

*NRT - Near-Real Time data (1-3 hour latency).
*DM - Delayed mode "scientific quality" SST. Produced on a 8-week delay.
*RAN2 - Reanalysis-2 of VIIRS SST (NPP: Feb'2012-Apr'2019; N20: Jan'2018-Apr'2019). Produced using ACSPO V2.61.
*RAN3 - Reanalysis-3 of VIIRS SST (NPP: Feb'2012-Dec'2021; N20: Jan'2018-Dec'2021). Produced using ACSPO V2.80.
NPP - Suomi NPP satellite platform
N20 - NOAA-20 satellite platform

Please acknowledge "NOAA CoastWatch/OceanWatch" when you use data from our site and cite the particular dataset DOI as appropriate.


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).


Afternoon: Suomi NPP / VIIRS, NOAA-20 / VIIRS


Measurement Oceans > Sea Surface Temperature > Sub-skin SST



Short Name


Sample Filename

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

Dataset Type


Processing Level

L2P and L3U

Spatial Coverage


Temporal Coverage

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


NRT: <6 hours
RAN: 8 weeks


L2P: 0.75km @ Nadir; ~1.5km @ swath edge
L3U: 0.02°


L2P: Satellite native swath (WGS84)
L3U: Equal-grid 0.02°

Swath Width

~3,000 km

Sample Frequency

1674 scans (push brooms) per 10min; each push broom = 16 detectors

Temporal Repeat

Twice Daily

Orbital Period

101 Minutes


Sun-synchronous, altitude 824km, inclination 98.74

Data Provider

Creator: NOAA STAR
Release Place: College Park, MD, USA
Release Date: 2016-Dec-31




NOAA, NPP, N20, S-NPP, NOAA-20, JPSS, VIIRS, reprocessing, RAN, RAN3, ACSPO, sea surface temperature, SST, L2P, L3U


(♦ - non-government website)

Data Citation: 

The ACSPO NPP/N20 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.

(♦ - non-government website)