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Description

The N21-VIIRS-L3U-ACSPO-v2.80 dataset produced by the NOAA ACSPO system derives the Subskin Sea Surface Temperature (SST) from the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Joint Polar Satellite System (JPSS)-2 satellite, renamed as NOAA-21 (N21). N21 was launched on Nov. 10, 2022, the 3rd satellite in the US NOAA latest JPSS series. <br><br>

The ACSPO N21 VIIRS L3U (Level 3 Uncollated) product is a gridded version of the ACSPO N21 VIIRS L2P product, also available at PO.DAAC (10.5067/GHV21-2P280). The L3U output files are 10-minute granules in netCDF4 format, compliant with the Group for High Resolution Sea Surface Temperature (GHRSST) Data Specification version 2 (GDS2). The ACSPO N21 VIIRS SST record is available back to 19 Mar 2023. There are 144 granules per 24 hour interval, with a total data volume of 0.6GB/day. Fill values are reported at all invalid pixels, including pixels >5 km inland. For each valid water pixel (defined as ocean, sea, lake or river, and up to 5 km inland), the following layers are reported: SST, a subset of variable l2p_flags (including day/night, land, ice, twilight, and glint flags), wind speed, and the SST minus reference CMC SST (Canadian Met Centre 0.1deg L4 SST, 10.5067/GHCMC-4FM03). Only L2P SSTs with QL=5 were gridded, so all valid SSTs are recommended for the users. Per GDS2 specifications, two additional Sensor-Specific Error Statistics layers (SSES bias and standard deviation) are reported in each pixel with valid SST. <br><br>

The ACSPO VIIRS L3U product is monitored and validated against quality controlled in situ data provided by NOAA in situ SST Quality Monitor system (iQuam) using another NOAA system, SST Quality Monitor (SQUAM).

Product Summary

Platforms
NOAA-21
Instruments
VIIRS
Spatial Extent

N: 90 S: -90 E: 180 W: -180

Spatial Resolution
0.02 Decimal Degrees x 0.02 Decimal Degrees
Geographic Region
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2023-03-19
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC) ,
Center for Satellite Applications and Research, NESDIS, NOAA, U.S. Department of Commerce (DOC/NOAA/NESDIS/STAR)
Concept ID
C2754899545-POCLOUD
Data State
ACTIVE
Number of Files/Granules
143188
Processing Level
3
Published
Updated
Science Keywords
Sea Surface Temperature

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

NOAA/NESDIS/STAR. (2023). GHRSST Level 3U NOAA ACSPO SST v2.80 from VIIRS on NOAA-21 Satellite [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/GHN21-3U280 Date Accessed: 2025-12-13

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
crs coordinate reference system N/A int N/A N/A 1
dt_analysis Deviation from reference SST, i.e., dt_analysis = SST - reference SST kelvin byte -128 -127 to 127 0.1
l2p_flags L2P common flags in bits 1-6 and data provider flags (from ACSPO mask) in bits 9-16: bit01 (0=IR: 1=microwave); bit02 (0=ocean; 1=land); bit03 (0=no ice; 1=ice); bits04-08 (reserved,set to 0); bit09 (0=radiance valid; 1=invalid); bit10 (0=night; 1=day); bit11 (0=ocean; 1=land); bit12 (0=good quality data; 1=degraded quality data due to &quot;twilight&quot; region); bit13 (0=no glint; 1=glint); bit14 (0=no snow/ice; 1=snow/ice); bits15-16 (00=clear; 01=probably clear; 10=cloudy; 11=clear-sky mask undefined) N/A short N/A -32768 to 32767 1
lat Latitudes for locating data degrees_north float N/A -90 to 90 1
lon Longitude for locating data degrees_east float N/A -180 to 180 1
or_number_of_pixels Original number of pixels from the L2Ps contributing to the SST value, not weighted 1 short 0 1 to 32767 1
quality_level SST quality levels: 5 corresponds to “clear-sky” pixels and is recommended for operational applications and validation. N/A byte -128 0 to 5 1
satellite_zenith_angle satellite zenith angle degrees short -32768 -32767 to 32767 0.01
sea_surface_temperature SST obtained by regression with buoy measurements, sensitive to skin SST. Further information at (Petrenko et al., JGR, 2014; doi:10.1002/2013JD020637) kelvin short -32768 -200 to 32767 0.01
sses_bias Bias is derived against Piecewise Regression SST produced by local regressions with buoys. Subtracting sses_bias from sea_surface_temperature produces more accurate estimate of SST at the depth of buoys. Further information at (Petrenko et al., JTECH, 2016; doi:10.1175/JTECH-D-15-0166.1) kelvin byte -128 -127 to 127 0.016
sses_standard_deviation Standard deviation of sea_surface_temperature from SST measured by drifting buoys. Further information at (Petrenko et al., JTECH, 2016; doi:10.1175/JTECH-D-15-0166.1) kelvin byte -128 -127 to 127 0.01
sst_dtime time plus sst_dtime gives seconds since 1981-01-01 00:00:00 UTC seconds int -2147483648 -2147483647 to 2147483647 0.25
sst_front_position Binary indicator of SST front position in the valid SST clear-sky domain: 1 - SST front present, 0 - no front present N/A byte -128 0 to 1 1
sst_gradient_magnitude Gradient magnitude calculated from SST field in all grids with valid SST kelvin/km short -32768 -32767 to 32767 0.001
time seconds since 1981-01-01 00:00:00 seconds since 1981-01-01 00:00:00 int N/A N/A 1
wind_speed Typically represents surface winds (10 meters above the sea surface) m s-1 byte -128 -127 to 127 0.2
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