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Description

This L3U (Level 3 Uncollated) dataset contains global daily Sea Surface Temperature (SST) on a 0.02 degree grid resolution. It is produced by the National Oceanic and Atmospheric Administration (NOAA) Advanced Clear Sky Processor for Ocean (ACSPO) using L2P (Level 2 Preprocessed) product acquired from the Meteorological Operational satellite A (Metop-A) Advanced Very High Resolution Radiometer 3 (AVHRR/3) (https://podaac.jpl.nasa.gov/dataset/AVHRRF_MA-STAR-L2P-v2.80 ) in Full Resolution Area Coverage (FRAC) mode as input. It is distributed as 10-minute granules in netCDF-4 format, compliant with the Group for High Resolution Sea Surface Temperature (GHRSST) Data Specification version 2 (GDS2). There are 144 granules per 24-hour interval. Fill values are reported in all invalid pixels, including land pixels with >5 km inland. For each valid water pixel (defined as ocean, sea, lake or river), and up to 5 km inland, the following major layers are reported: SSTs and ACSPO clear-sky mask (ACSM; provided in each grid as part of l2p_flags, which also includes day/night, land, ice, twilight, and glint flags). Only input 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. Ancillary layers include wind speed and ACSPO minus reference Canadian Meteorological Centre (CMC) Level 4 (L4) SST. The ACSPO Metop-A AVHRR FRAC L3U product is monitored and validated against iQuam in situ data (Xu and Ignatov, 2014) in the NOAA SST Quality Monitor (SQUAM) system (Dash et al, 2010). SST imagery and clear-sky mask are evaluated, and checked for consistency with L2P and other satellites/sensors SST products, in the NOAA ACSPO Regional Monitor for SST (ARMS) system. More information about the dataset is found at AVHRRF_MA-STAR-L2P-v2.80 and in (Pryamitsyn et al., 2021).

Product Summary

Platforms
METOP-A
Instruments
AVHRR-3
Spatial Extent

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

Spatial Resolution
0.02 Decimal Degrees x 0.02 Decimal Degrees
Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2006-12-01 to 2021-11-14
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
C2205121413-POCLOUD
Data State
COMPLETE
Number of Files/Granules
777522
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

NASA/JPL. (2021). GHRSST NOAA/STAR Metop-A AVHRR FRAC ACSPO v2.80 0.02?? L3U Dataset (GDS v2) [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/GHMTA-3US28 Date Accessed: 2026-04-17

Documents

USER'S GUIDE

SCIENCE DATA PRODUCT VALIDATION

DATA CITATION GUIDELINES

PUBLICATIONS

GENERAL DOCUMENTATION

Variables

The table below lists the variables contained within a single granule for this dataset. Variables often contain observed or derived geophysical measurements collected from a variety of sources, including remote sensing instruments on satellite and airborne platforms, field campaigns, in situ measurements, and model outputs. The terms variable, parameter, scientific data set, layer, and band have been used across NASA’s Earth science disciplines; however, variable is the designated nomenclature in NASA’s Common Metadata Repository (CMR). Variable metadata attributes such as Name, Description, Units, Data Type, Fill Value, Valid Range, and Scale Factor allow users to efficiently process and analyze the data. The full range of attributes may not be applicable to all variables. Additional information on variable attributes is typically available in the data, user guide, and/or other product documentation.

For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor Offset
crs coordinate reference system N/A int N/A N/A 1 N/A
dt_analysis Deviation from reference SST, i.e., dt_analysis = SST - reference SST kelvin byte -128 -127 to 127 0.1 N/A
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 "twilight" 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 N/A
lat Latitudes for locating data degrees_north float N/A -90 to 90 1 N/A
lon Longitude for locating data degrees_east float N/A -180 to 180 1 N/A
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 N/A
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 N/A
satellite_zenith_angle satellite zenith angle degrees short -32768 -32767 to 32767 0.01 N/A
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 0.01 273.15
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 N/A
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 1
sst_dtime time plus sst_dtime gives seconds since 1981-01-01 00:00:00 UTC seconds int -2147483648 -2147483647 to 2147483647 0.25 N/A
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 N/A
sst_gradient_magnitude Gradient magnitude calculated from SST field in all grids with valid SST kelvin/km short -32768 -32767 to 32767 0.001 N/A
time seconds since 1981-01-01 00:00:00 seconds since 1981-01-01 00:00:00 int N/A N/A 1 N/A
wind_speed Typically represents surface winds (10 meters above the sea surface) m s-1 byte -128 -127 to 127 0.2 25.4
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