AVHRR GAC Reanalysis 2 (RAN2) dataset is an improved and extended version of AVHRR GAC RAN1 (Ignatov et al., 2016). RAN2 is produced from 5 AVHRR/2s (onboard N07/09/11/12/14) and 5 AVHRR/3s (N15/16/17/18/19) using the NOAA Advanced Clear-Sky Processor for Ocean (ACSPO) enterprise system v2.81. At the time of release, it covers from 1 Sep 1981 to 31 Dec 2021 and will be periodically extended as new L1b data from N15/18/19 arrive. Out of ten satellites, seven (N07/09/11/14/16/18/19) were initially launched into afternoon orbits (1:30pm/am), two (N12/15) into early-morning orbits (7:30pm/am), and one (N17) into mid-morning orbit (10am/pm). All NOAA orbits are not controlled and evolve in time. The RAN2 dataset is documented in (Petrenko et al. 2020 and 2021; Pryamitsyn et al. 2020).

AVHRR FRAC onboard three Metop-First Generation (FG) satellites have been processed separately. AVHRR FRAC RAN1 dataset is available at  ACSPO Global SST from AVHRR FRAC.

The data are reported in GHRSST Data Specifications v2 (GDS2) format, in three projections: swath (L2P), 0.02° gridded L3U (U=uncollated) and 0.02° gridded L3C (C=collated). L2P and L3U products are aggregated into 10min granules, 144 per day, with a total daily data volumes of 0.27GB/L2P and 0.32GB/L3U. L3C product contains two collated files per day, daily volume of 0.3GB/day, : one file  for the daytime SST and one for the nighttime SST.  ACSPO retrievals are made in full AVHRR swath (~2,800 km). For data assimilation applications (such as production of L4 analyses, especially those blending satellite and in situ data), subtraction of the Sensor-Specific Error Statistics (SSES; Petrenko et al., 2016) biases reported in ACSPO files, is recommended.

In each valid water pixel (defined as ocean, sea, lake or river, up to 5km inland), the following layers are reported in both L2P and L3U: SSTs derived using Non-Linear SST (NLSST) algorithms (Petrenko et al., 2020); ACSPO clear-sky mask (ACSM; provided in each pixel as part of l2p_flags; Petrenko et al., 2010); SSES bias and standard deviation (Petrenko et al., 2016); MERRA-2 wind speed; and ACSPO SST minus reference SST (ESA CCI L4 SST from 1 Sep 1981 - 31 Aug 1991; switched to CMC L4 SST from 1 Sep 1991 to present time). In "invalid" pixels (defined as those with >5km inland), fill values are reported.

Only ACSM "confidently clear" pixels (equivalent to GDS2 "quality level"=5; QLs are also reported for each pixel) should be used. The ACSM also provides day/night, land, ice, twilight, and glint flags.

All L2P, L3U and L3C SSTs are monitored and validated against in situ data  iQuam (Xu and Ignatov, 2014) in SQUAM (Dash et al., 2010), and BTs are monitored in MICROS (Liang and Ignatov, 2011). The AVHRR sensors calibration and characterization, and orbital stability of NOAA satellites, are monitored in the NOAA 3S system (He et al., 2016)



NOAA-07  ( 1 Sep 2002 - 01 Feb 1985)
NOAA-09  (25 Feb 1985 - 07 Nov 1988)
NOAA-11  (11 Nov 1988 - 13 Sep 1994)
NOAA-14  (20 Jan 1995 - 19 Oct 2001)

NOAA-16 (01 Jan 2001 - 30 Sep 2007)
NOAA-18  (06 Jun 2005 - 18 Oct 2021)
NOAA-19  (22 Feb 2009 - 18 Oct 2021)


NOAA-12  (16 Sep 1991 - 14 Dec 1998)

NOAA-15 ( 1 Nov 1998 - 18 Oct 2021)


NOAA-17  ( 7 Jul 2002 - 8 Mar 2010)


Measurement Oceans > Sea Surface Temperature > Sub-skinSST



Short Name


Sample Filename



Dataset Type


Processing Level

L2P and L3U

Spatial Coverage


Temporal Coverage

1 Sep 1981 - 18 Oct 2021, to be extended



L2P: 4km @Nadir; ~25km @swath edge
L3U: 0.02°


L2P: Satellite native swath (WGS84)
L3U: Equal-grid 0.02°

Swath Width

~2,800 km

Sample Frequency

2 scan lines per 1 second

Temporal Repeat

Twice Daily

Orbital Period

101 Minutes


Various Sun-synchronous
PM NOAA-07/09/11/14/16/18/19: initially launched into 1:30am/pm orbits, drift in time
Mid-AM NOAA-17: initially launched into 10am/pm orbit, drifts in time
Early-AM NOAA-12/15: initially launched into 7:30am/pm orbit, drifts in time

Data Provider

Creator: NOAA STAR
Release Place: College Park, MD, USA
Release Date: 2021-Dec-21





Keywords (Beta)

Algorithms and Evaluation

Petrenko, B., A. Ignatov, Y. Kihai, and A. Heidinger, 2010: Clear-Sky Mask for ACSPO. JTech, 27, 1609-1623, doi:10.1175/2010JTECHA1413.1

Petrenko, B., A. Ignatov, Y. Kihai, J. Stroup, P. Dash, 2014: Evaluation and Selection of SST Regression Algorithms for JPSS VIIRS. JGR, 119, 4580-4599, doi:10.1002/2013JD020637

Petrenko, B., A. Ignatov, Y. Kihai, P. Dash, 2016: Sensor-Specific Error Statistics for SST in the Advanced Clear-Sky Processor for Oceans. JTech, 33, 345-359, doi:10.1175/JTECH-D-15-0166.1

Ignatov, A., X. Zhou, B. Petrenko, X. Liang, Y. Kihai, P. Dash, J. Stroup, J. Sapper, & P. DiGiacomo, 2016: AVHRR GAC SST Reanalysis Version 1 (RAN1). Remote Sens., 8(4), 315,doi: 10.3390/rs6040315,

Petrenko B., V. Pryamitsyn, , A. Ignatov,  & Y. Kihai, 2020: SST and cloud mask algorithms in reprocessing 1981-2002 NOAA AVHRR data for SST with the Advanced Clear-Sky Processor for Oceans (ACSPO). SPIE Defense + Commercial Sensing, 11420, SI, www.spiedigitallibrary.org,

Pryamitsyn, V., A. Ignatov, B. Petrenko, O. Jonasson  & Y. Kihai, 2020:  Evaluation of the initial NOAA AVHRR GAC SST reanalysis version 2 (RAN2 B01). SPIE Defense + Commercial Sensing, 11420I, https://doi.org/10.1117/12.2558660,

Petrenko, B.; Pryamitsyn, V.; Ignatov, A. 2021;Filtering cold outliers in SSTs retrieved from early AVHRRs for the second AVHRR GAC reanalysis. SPIE Defense + Commercial Sensing , 11752, https://doi.org/10.1117/12.2585908


Dash, P., A. Ignatov, Y. Kihai & J. Sapper, 2010: The SST Quality Monitor (SQUAM). JTech, 27, 1899-1917, doi:10.1175/2010JTECHO756.1, www.star.nesdis.noaa.gov/sod/sst/squam/

Ding, Y., A. Ignatov, I. Gladkova, M. Crosberg, and C. Chu, 2017: ACSPO Regional Monitor for SST (ARMS). BoM - NOAA SST Workshop, 18-21 April 2017, Melbourne, Australia (presentation), www.star.nesdis.noaa.gov/sod/sst/arms/

Liang, X. & A. Ignatov, 2011: Monitoring of IR Clear-sky Radiances over Oceans for SST (MICROS). JTech, 28, 1228-1242, doi:10.1175/JTECH-D-10-05023.1, www.star.nesdis.noaa.gov/sod/sst/micros/

Xu, F. & A. Ignatov, 2014: In situ SST Quality Monitor (iQuam). JTech, 31, 164-180, doi:10.1175/JTECH-D-13-00121.1, www.star.nesdis.noaa.gov/sod/sst/iquam/ He, K.; Ignatov, A.; Kihai, Y.; Cao, C.Y.; Stroup, J. 2016; Analyzing Avhrr Thermal Calibration Using Sensor Stability for Sst (3s) System. 2016 Ieee International Geoscience and Remote Sensing Symposium (Igarss) , 1950-1953, https://doi.org/10.1109/Igarss.2016.7729502

(♦ - non-government website)

Data Citation: 

Pryamitsyn, V.; Ignatov, A.; Petrenko, B.; Jonasson, O.; Kihai, Y. Evaluation of the initial NOAA AVHRR GAC SST Reanalysis Version 2 (RAN2 B01). SPIE Defense + Commercial Sensing 2020, 11420, https://doi.org/10.1117/12.2558751

The ACSPO AVHRR GAC RAN data are provided by NOAA STAR. We strongly recommend contacting NOAA SST team led by A. Ignatov before the data are used for any publication or presentation.