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: Time Series Collection Reanalysis v2 (RAN2)*

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: RAN2* + NRT*

Product Resource Locator
NPP L2P 10.5067/GHVRS-2PO61
N20 L2P 10.5067/GHV20-2PO61
NPP L3U 10.5067/GHVRS-3UO61
N20 L3U 10.5067/GHV20-3UO61

NCEI Archive: RAN2* + 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
*RAN2 - Reanalysis-2 of VIIRS SST (NPP: Feb'2012-Apr'2019; N20: Jan'2018-Apr'2019). Later dates are supplemented using NRT data.
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 hr interval, with a total data volume of ~25 GB/day for L2P, and ~0.4 GB/day for L3U.

The near real-time (NRT) data is operationally produced by the NOAA Data Exploitation (NDE) using the official enterprise ACSPO algorithms. The NRT L2P/L3U data are produced using ACSPO v2.61. 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 v2.61 and therefore containes SST data from earlier ACSPO versions before the operational implementation of v2.61 (23 Apr 2019), while PO.DAAC contains the full v2.61 archive.

The Reanalysis version 2 (RAN2) product was produced at STAR using ACSPO v2.61. L2P and L3U RAN2 data covers a period from 1 Feb 2012 - present 2019 for NPP and Jan 5 2018 - present for N20. A complete archive of L2P/L3U data is available on PO.DAAC, while the the coastwatch ftp only contains L3U data due to high data volume. 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 RAN2, are similar to those described in (Ignatov et al., 2016) for AVHRR GAC, except fixed regression coefficients were used (in contrast with variable coefficients for AVHRR). Currently, the RAN2 data are available on this Coast Watch site (L3U) and PO.DAAC (L2P and L3U).

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.

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); NCEP wind speed; and ACSPO SST minus reference (Canadian Met Centre L4 SST). For L2P, layers of brightness temperatures (BTs) in M12, 15, and 16 are also reported, for those users interested in direct "radiance assimilation" (e.g., NOAA NCEP, NASA GMAO).

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 BTs and SSTs in those pixels. They may also ignore ACSPO SST, and derive their own SSTs from the original BTs.

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 BTs 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_V2.61-v02.0-fv01.0.nc 
L3U: 20120301001000-OSPO-L3U_GHRSST-SSTsubskin-VIIRS_NPP-ACSPO_V2.61-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: 2 weeks (target)


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, RAN2, ACSPO, sea surface temperature, SST, L2P, L3U


(♦ - non-government website)

Data Citation: 

The ACSPO NPP/N20 VIIRS RAN2 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)