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Description

A Group for High Resolution Sea Surface Temperature (GHRSST) global Level 4 sea surface temperature dataset is produced daily on a 0.25 degree grid at the NOAA National Centers for Environmental Information. This product uses optimal interpolation (OI) by interpolating and extrapolating SST observations from different sources, resulting in a smoothed complete field. The sources of data are satellite (AVHRR) and in situ platforms (i.e., ships, buoys, and Argo floats above 5m depth), and the specific datasets employed may change over time. In the regions with sea-ice concentration higher than 30%, freezing points of seawater are used to generate proxy SSTs. A preliminary version of this dataset is produced in near-real time (1-day latency), and then replaced with a final version after 2 weeks. The v2.1 (Huang et al. 2021) is updated from the previous AVHRR_OI-NCEI-L4-GLOB-v2.0 data. Major improvements include: 1) In-situ ship and buoy data changed from the NCEP Traditional Alphanumeric Codes (TAC) to the NCEI merged TAC + Binary Universal Form for the Representation (BUFR) data, with large increases of buoy data included to correct satellite SST biases; 2) Addition of Argo float observed SST data as well, for further correction of satellite SST biases; 3) Satellite input from the METOP-A and NOAA-19 to METOP-A and METOP-B, removing degraded satellite data; 4) Revised ship-buoy SST corrections for improved accuracy; and 5) Revised sea-ice-concentration to SST conversion to remove warm biases in the Arctic region. These updates only apply to data after January 1st, 2016. The data pre 2016 are still the same as v2.0 except for metadata upgrades. NCEI has panned to update the entire dataset from 1982 to fix the In-Situ data ingest and bias correction which exist prior 2016.

Product Summary

Platforms
NOAA-11 ,
NOAA-14 ,
NOAA-9 ,
NOAA-16 ,
NOAA-17 ,
NOAA-19 ,
METOP-A ,
METOP-B ,
NOAA-7
Instruments
AVHRR-2 ,
AVHRR-3
Spatial Extent

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

Spatial Resolution
0.25 Decimal Degrees x 0.25 Decimal Degrees
Geographic Region
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2016-01-01
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC) ,
National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce (DOC/NOAA/NESDIS/NCEI)
Concept ID
C2036881712-POCLOUD
Data State
ACTIVE
Number of Files/Granules
3632
Processing Level
4
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. (2020). GHRSST Level 4 AVHRR_OI Global Blended Sea Surface Temperature Analysis (GDS2) from NCEI [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/GHAAO-4BC21 Date Accessed: 2025-12-14

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
analysed_sst Single-sensor Pathfinder 5.0/5.1 AVHRR SSTs used until 2005; two AVHRRs at a time are used 2007 onward. Sea ice and in-situ data used also are near real time quality for recent period. SST (bulk) is at ambiguous depth because multiple types of observations are used. kelvin short -32768 -300 to 4500 0.01
analysis_error Sum of bias, sampling and random errors. kelvin short -32768 0 to 32767 0.01
lat Uniform grid with centers from -89.875 to 89.875 by 0.25 degrees degrees_north float N/A -90 to 90 1
lat_bnds This variable defines the latitude values at the north and south bounds of every 0.25-degree pixel. degrees_north float N/A N/A 1
lon Uniform grid with centers from -179.875 to 179.875 by 0.25 degrees degrees_east float N/A -180 to 180 1
lon_bnds This variable defines the longitude values at the west and east bounds of every 0.25-degree pixel. degrees_east float N/A N/A 1
mask Several masks distinguishing between water, land and ice. N/A byte -128 1 to 31 1
sea_ice_fraction 7-day median filtered. Switch from 25 km NASA team ice (http://nsidc.org/data/nsidc-0051.html) to 50 km NCEP ice (http://polar.ncep.noaa.gov/seaice) after 2004 results in artificial increase in ice coverage. 1 byte -128 0 to 100 0.01
time Nominal time because observations are from different sources and are made at different times of the day. seconds since 1981-01-01 00:00:00 int N/A N/A 1
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