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AVHRR Pathfinder SST v5.3

AVHRR Pathfinder version 5.3 level 3 collated (L3C) global 4km sea surface temperature (NOAA NCEI AVHRR Pathfinder SST climate data record, 4 km day/night L3C)

Discontinued

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No longer updated

Through a NOAA NESDIS Notice of Changes posted on 2025-09-03, NCEI announced that it has discontinued the AVHRR Pathfinder SST product and Climate Data Record, with no updates beyond 2023-12-31. The NCEI product page states "This product is no longer updated. The period of record is 1981–2023.", and on 2026-10-13 the NCEI archive record (accession) was marked "Complete". The archived data remain authoritative and available from NCEI.

Successor: None (no successor announced by NCEI) — Neither the discontinuation notice nor the product page names a successor. The "future version" plans on the product page (filling the 1994–1995 gap, populating empty variables and so on) remain unscheduled. If you need a satellite SST climate record that includes AVHRR and continues past 2023, consider ESA SST CCI CDR v3 (from 1980, extended daily by an ICDR), but do not splice it onto this record: the processing systems differ.

At a glance

Item Details
Section Satellite › Sea surface temperature (also listed in: Ocean › Satellite products)
Type Satellite product
Domains Ocean, Remote sensing
Provider NOAA National Centers for Environmental Information (NCEI)
Period 1981-08 ~ 2023-12
Coverage Global — Global ocean. An L3 product with gaps where there is cloud, sea ice or low quality (no gap filling). l2p_flags marks land, ice, lakes and rivers
Horizontal resolution 0.0416667° equal-angle latitude–longitude grid of 8640 × 4320 (global; latitude ordered from 90°N to 90°S). The algorithm document gives about 4.63 km per bin at the equator
Vertical resolution Single sea-surface value — skin SST
Temporal resolution Two files per day — separate daytime and nighttime daily L3C files (observations from one satellite collated onto a daily grid). Version 5.3 has no monthly or 8-day composites
Update frequency Discontinued — the last data date is 2023-12-31 (discontinuation notice of 2025-09-03)
Licence Open data; the file attribute reads "These data are available for use without restriction." NCEI makes no warranty for the data and asks users to credit them with "These data were provided by GHRSST and the NOAA National Centers for Environmental Information."
Account required No

Note on period: The NCEI archive record covers 1981-08-25 to 2023-12-31 (the NOAA CoastWatch ERDDAP copy has the same range). The 2023 files come from AVHRR/3 on NOAA-19. NCEI notes that part of September 1994 to February 1995 was temporarily filled with the earlier PFV5.0 data because of a gap in the source data, and that previous-year aerosol values were used in that period.

How to read the resolution
  • Horizontal resolution lists both the native model grid and the grid you download, as given in the official documentation. The same dataset can come on different grids from different providers or products, so check the grid of your downloaded file.
  • Grid spacing is not the effective resolution. A provided grid that is finer than the native one carries no extra information.
  • Intervals and whether a value is instantaneous, mean or accumulated differ between variables — see 'Available variables' below.
  • The 'provided resolution' in lists and the comparison table is a simplified km/degree value for quick comparison. Use this page for exact values.

Overview

A long-term climate data record of skin SST, consistently reprocessed from 4 km GAC observations by the Advanced Very High Resolution Radiometer (AVHRR) on NOAA polar-orbiting weather satellites since 1981. SST is computed with a non-linear regression algorithm whose coefficients come from matchups of in situ and satellite data (Kilpatrick et al. 2001), within a processing system rebuilt on NASA SeaDAS 6.4, and is delivered as daily L3C files split into day and night. The values are satellite observations without statistical gap filling, so unlike an analysis they exist only where and when the sensor actually saw the sea. Version 5.3, the last version, adds quality level 0 data, better sun glint handling and an updated land mask compared with 5.2; updates ended with 2023.

What changes with the successor

AVHRR Pathfinder v5.2 → AVHRR Pathfinder v5.3

Transition: 2016-08

A rebuild on SeaDAS 6.4 that adds quality level 0 data and improves sun glint and land-boundary handling and metadata conventions. The record was also extended from 2012 to 2023.

Aspect AVHRR Pathfinder v5.2 AVHRR Pathfinder v5.3
Period 1981-09-01 to 2012-12-31 1981-08-25 to 2023-12-31
DOI 10.7289/v5wd3xhb 10.7289/v52j68xx
Quality levels Quality level 0 data excluded Quality level 0 data included; daytime SST above 39.8°C flagged with l2p_flags bit 6
Cloud and sun glint handling NOAA-7 and NOAA-19 cloud tests differed from other sensors Consistent cloud tree tests, better sun glint handling, improved flagging of land–water boundary hot spots
Masks Earlier land mask Land mask from the Global Lakes and Wetlands Database; Antarctic ice shelves flagged as 100% ice
File format netCDF-4 netCDF-4 classic with improved CF and ACDD compliance

Things to watch when switching

  • Pixel values and missing pixels differ between 5.2 and 5.3, so do not mix them in one series; download the whole period in 5.3.
  • Quality level 0 is now included, so re-check your quality_level and pathfinder_quality_level filters if you want to match 5.2-era screening.
  • The high-latitude solstice errors are not fixed in 5.3.

Sources: NCEI — AVHRR Pathfinder SST product page (5.3 changes, version history) · NCEI archive record — v5.3 L3C

Available variables

Names follow the attributes of the v5.3 L3C files on NCEI THREDDS. Values are packed as integers (scale_factor, add_offset), so make sure your library unpacks them. sses_bias, sses_standard_deviation and sst_dtime are empty in 5.3.

Time-stamp convention — instantaneous, mean or accumulated? — click to show

Each day or night file collates one satellite's orbits for one day onto the 4 km grid, so each value is the skin temperature at the satellite overpass time (not a daily mean). The data-day does not start at 00 UTC but when the satellite crosses the 180° meridian near the equator, so one file mixes observations from two UTC dates.

  • Example: the 2023001 night file (NOAA-19) has time_coverage_start 2022-12-31 09:58 UTC and time_coverage_end 2023-01-01 19:06 UTC. Read the date as a data-day label.
  • sst_dtime, which would give per-pixel observation times, is empty in 5.3, so exact pixel times are unavailable; the time variable is only the file reference time.
  • Daytime skin SST keeps the diurnal warming of the surface layer. Use the night files to reduce diurnal effects.
  • Overpass local time changes with the satellite. In the algorithm document's table, only NOAA-17 (2002-07 to 2005-06) is a morning satellite (nominal 10:00 local time) and the rest are afternoon satellites, so account for this when comparing daytime SST over the long term.
  • dt_analysis is the difference from the previous day's SST analysis, an auxiliary field for spotting unusual values.

Source: AVHRR Pathfinder v5.3 Algorithm Description (NCEI) and v5.3 L3C file attributes

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

Sea surface temperature (L3C day and night files)

Variable Short name Units Time convention Notes
Skin sea surface temperature sea_surface_temperature K instantaneous Skin temperature at the overpass time (scale_factor 0.01, add_offset 273.15); separate day and night files
Deviation from the previous day's SST analysis dt_analysis K instantaneous scale_factor 0.1

Quality information

Variable Short name Units Time convention Notes
GHRSST quality level quality_level 0–5 instantaneous 0 no_data, 1 bad_data, 2 worst_quality, 3 low_quality, 4 acceptable_quality, 5 best_quality
Native Pathfinder quality level pathfinder_quality_level 0–7 instantaneous 0 is worst and 7 best, -1 is missing (per the file attributes)
L2P flags l2p_flags bit flags instantaneous Marks microwave, land, ice, lake and river. According to the product page, 5.3 adds bit 6 for daytime SST above 39.8°C

Ancillary fields

Variable Short name Units Time convention Notes
Sea ice fraction sea_ice_fraction percent day mean scale_factor 0.01 · OSI SAF sea ice (NOAA OISST as fallback) regridded to 4 km. Its internal time definition was not confirmed
10 m wind speed wind_speed m s-1 instantaneous NCEP/DOE reanalysis winds. How they are matched to the overpass time was not confirmed
Aerosol dynamic indicator aerosol_dynamic_indicator percent instantaneous 0.63 µm aerosol optical thickness over cloud-free, non-glint water. NCEI calls it sub-optimal because it combines two sources

The full variable list is in the official documentation.

How to get the data

Example code

Opens one night file through the NCEI THREDDS OPeNDAP address and clips the area around the Korean Peninsula. No login is needed. Latitude runs north to south, so the slice starts from the larger value.

# pip install xarray netCDF4
import xarray as xr

url = ("https://www.ncei.noaa.gov/thredds-ocean/dodsC/pathfinder/Version5.3/L3C/2023/data/"
       "20230101023227-NCEI-L3C_GHRSST-SSTskin-AVHRR_Pathfinder-PFV5.3_NOAA19_G_2023001_night-v02.0-fv01.0.nc")
ds = xr.open_dataset(url)

sub = ds.sel(lat=slice(40, 30), lon=slice(120, 135))              # around Korea
sst = sub["sea_surface_temperature"].where(sub["quality_level"] >= 4) - 273.15   # levels 4-5 only, K -> °C
print(float(sst.count()), float(sst.mean()))

Practical tips

  • This is gap-containing L3 data, so daily files over the East Sea and Yellow Sea have many gaps in the cloudy monsoon season and in winter. Check the number of valid pixels per day when computing climatologies or monthly means.
  • The file defines quality_level values (0 no_data to 5 best_quality), but the NCEI pages give no official threshold. State which levels you used and test how sensitive your results are to that choice.
  • An NCEI technical note says v5.2 and v5.3 SST above 50° latitude is often wrong near the June and December solstices (SeaDAS did not split mixed day/night granules properly). Treat those periods with care in high-latitude seasonal studies.
  • September 1994 to February 1995 was temporarily filled with earlier-version data, with previous-year aerosol values. Check any trend or climatology that includes this period separately.
  • A very small share of daytime SST values exceed 39.8°C. Version 5.3 marks them with bit 6 of l2p_flags, so check that bit when looking at extreme warm cases in the tropics or along coasts.
  • For data after 2023 you have to move to another product. Do not splice records from different processing systems into one series; compare them over an overlapping period first.

Notices and change history

2025-09-03 · Critical · AVHRR Pathfinder SST product and CDR discontinued (no updates after 2023-12-31)

In a NOAA NESDIS Notice of Changes, NCEI announced that the AVHRR Pathfinder SST product and Climate Data Record are discontinued, with no updates beyond 2023-12-31. All archived data remain authoritative and available from the product and CDR pages. No successor was mentioned.

Read the original

2019-08-29 · Info · PO.DAAC retires Pathfinder v5.0 and v5.1

NASA PO.DAAC stopped supporting NOAA AVHRR Pathfinder SST v5.0 and v5.1 and directed users to NOAA NCEI, which hosts these and newer versions.

Read the original

2016-08-27 · Info · Release of Pathfinder v5.3 L3C

NCEI published v5.3 L3C, reprocessed on SeaDAS 6.4. Changes from 5.2 include quality level 0 data, improved sun glint handling, consistent cloud tests for NOAA-7 and NOAA-19, and an updated land mask.

Read the original

2016-07-20 · Warning · High-latitude SST errors near the solstices in v5.2 and v5.3

An NCEI technical note (CDRP-RPT-0831) reported that Pathfinder v5.2 and v5.3 SST above 50° latitude is often incorrect near the June and December solstices. The cause is improper splitting of mixed day/night granules, which affects L3C; NCEI said it would fix this in a future version, but updates ended without one.

Read the original

References for your paper

Double-check before using in a paper

The citations below were compiled by the maintainer and may contain errors. Always double-check DOIs, authors, years and access-date formats against the provider's official dataset page and your journal's guidelines.

Dataset citation

AVHRR Pathfinder v5.3 L3C (NCEI) — DOI 10.7289/v52j68xx

Saha, Korak; Zhao, Xuepeng; Zhang, Huai-min; Casey, Kenneth S.; Zhang, Dexin; Baker-Yeboah, Sheekela; Kilpatrick, Katherine A.; Evans, Robert H.; Ryan, Thomas; Relph, John M. (2016). AVHRR Pathfinder version 5.3 level 3 collated (L3C) global 4km sea surface temperature for 1981-2023. NOAA National Centers for Environmental Information. Dataset. https://doi.org/10.7289/v52j68xx

Show BibTeX 
@misc{saha2016pathfinder53,
  author    = {Saha, Korak and Zhao, Xuepeng and Zhang, Huai-min and Casey, Kenneth S. and Zhang, Dexin and Baker-Yeboah, Sheekela and Kilpatrick, Katherine A. and Evans, Robert H. and Ryan, Thomas and Relph, John M.},
  title     = {{AVHRR} Pathfinder version 5.3 level 3 collated ({L3C}) global 4km sea surface temperature for 1981-2023},
  year      = {2016},
  publisher = {NOAA National Centers for Environmental Information},
  doi       = {10.7289/v52j68xx}
}

Reference papers

Pathfinder programme overview (requested by NCEI) — DOI 10.1007/978-90-481-8681-5_16

Casey, K. S., Brandon, T. B., Cornillon, P., Evans, R. (2010): The Past, Present, and Future of the AVHRR Pathfinder SST Program. In: Oceanography from Space, Springer Netherlands, 273–287.

Show BibTeX 
@incollection{casey2010pathfinder,
  author    = {Casey, Kenneth S. and Brandon, Tess B. and Cornillon, Peter and Evans, Robert},
  title     = {The Past, Present, and Future of the {AVHRR} Pathfinder {SST} Program},
  booktitle = {Oceanography from Space},
  publisher = {Springer Netherlands},
  pages     = {273--287},
  year      = {2010},
  doi       = {10.1007/978-90-481-8681-5_16}
}

Pathfinder SST algorithm and matchup database — DOI 10.1029/1999JC000065

Kilpatrick, K. A., Podestá, G. P., Evans, R. (2001): Overview of the NOAA/NASA advanced very high resolution radiometer Pathfinder algorithm for sea surface temperature and associated matchup database. Journal of Geophysical Research: Oceans, 106(C5), 9179–9197.

Show BibTeX 
@article{kilpatrick2001pathfinder,
  author  = {Kilpatrick, K. A. and Podest{\'a}, G. P. and Evans, R.},
  title   = {Overview of the {NOAA/NASA} advanced very high resolution radiometer Pathfinder algorithm for sea surface temperature and associated matchup database},
  journal = {Journal of Geophysical Research: Oceans},
  volume  = {106},
  number  = {C5},
  pages   = {9179--9197},
  year    = {2001},
  doi     = {10.1029/1999JC000065}
}

Acknowledgements

NCEI asks users to credit the data with "These data were provided by GHRSST and the NOAA National Centers for Environmental Information." and to cite Casey et al. (2010) along with the dataset DOI.

If this page helped, please acknowledge the Korean Climate Data Navigator

Please add the sentence below to the Acknowledgements of your paper.

Acknowledgements

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).