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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 C (Metop-C) Advanced Very High Resolution Radiometer 3 (AVHRR/3) (https://podaac.jpl.nasa.gov/dataset/AVHRRF_MC-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-C 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_MC-STAR-L2P-v2.80 and in (Pryamitsyn et al., 2021).

Product Summary

Platforms
METOP-C
Instruments
AVHRR-3
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
2018-12-04
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
C2205121433-POCLOUD
Data State
ACTIVE
Number of Files/Granules
365120
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-C 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/GHMTC-3US28 Date Accessed: 2025-12-14

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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 "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
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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