NOAA ACSPO Level 2P Global Sub-skin SST from AVHRR GAC Reanalysis version 1 (RAN1)

This AVHRR/3 GAC L2P Reanalysis 1 (RAN1) SST dataset is produced at NOAA STAR using the ACSPO system, from 3 afternoon (NOAA-16, -18, -19) and 2 mid-morning satellites (NOAA-17, Metop-A; two satellites at a time). The data are reported in hourly granule files in GHRSST Data Specifications v2 (GDS2) format and cover a period from 30 Aug 2002 31 Dec 2015. Work is underway to extend the period covered by RAN using AVHRR-2 data, initially to 1994, and eventually to 1981.

ACSPO retrievals are made in full AVHRR swath (~2,800 km). For data assimilation applications (such as production of L4 analyses, especially for those blending satellite and in situ data), correction for the single scanner error statistics (SSES; reported in ACSPO files) biases is strongly recommended.

In each valid water pixel (defined as ocean, sea, lake or river, up to 5km inland; fill values are reported in "invalid" pixels, at >5km inland), the following layers are reported, among others: brightness temperatures in AVHRR bands 3 (centered at 3.7 µm), 4 (11 µm), and 5 (12 µm); SSTs derived from BTs using multi-channel SST (MCSST; night) and Non-Linear SST (NLSST; day) algorithms (Petrenko et al., 2014); and ACSPO clear-sky mask (ACSM; provided in each pixel as part of l2p_flags) (Petrenko et al., 2010).

Only ACSM "confidently clear" pixels (equivalent to GDS2 "quality level"=5, also reported for each pixel) should be used. The ACSM also provides day/night, land, ice, twilight, and glint flags. Note that users of ACSPO data have the flexibility to ignore the ACSM, derive their own clear-sky mask, and use BTs and SSTs in those pixels. They may also ignore ACSPO SST, and derive their own SST from the original BTs.

RAN1 products are monitored and validated against in situ data (Xu and Ignatov, 2014) in SQUAM (Dash et al, 2010) and MICROS (Liang and Ignatov, 2011).

Key	Description
Platform/Sensor	Afternoon: NOAA-16 / AVHRR-3 (30 Aug 2002 06 Jun 2005) NOAA-18 / AVHRR-3 (07 Jun 2005 21 Feb 2009) NOAA-19 / AVHRR-3 (22 Feb 2009 31 Dec 2015) Mid-morning: NOAA-17 / AVHRR-3 (30 Aug 2002 22 Nov 2006) Metop-A / AVHRR-3 (23 Nov 2006 31 Dec 2015)
Measurement	Measurement Oceans > Sea Surface Temperature > Sub-skin SST
DOI	10.3390/rs6040315
Short Name	AVHRR_GAC_RAN1_L2P
Sample Filename	20100104050000-STAR-L2P_GHRSST-SSTsubskin-AVHRR19_G-ACSPO_V2.40-v02.0-fv01.0.nc
Dataset Type	Open
Processing Level	2P
Spatial Coverage	Global 180W-180E 90N-90S
Temporal Coverage	30 August 2002 to 31 December 2015
Resolution	4km @Nadir; ~30km @swath edge
Projection	Satellite native swath WGS84
Latency	N/A
Swath Width	~2,800 km
Sample Frequency	2 scan lines per 1 second
Temporal Repeat	Twice Daily
Orbital Period	101 Minutes
Orbit	Various
Data Provider	Creator: NOAA STAR Release Place: College Park, MD, USA Release Date: 2016-Apr-30
Keywords	NOAA, AVHRR, reprocessing, RAN1, ACSPO, sea surface temperature, SST, L2P
Formats	NetCDF

Data are available through the following servers:

Service	Resource Locator
FTP (anonymous)	ftp://ftp.star.nesdis.noaa.gov/pub/socd2/coastwatch/sst/ran/avhrr_gac/
THREDDS	https://www.star.nesdis.noaa.gov/thredds/socd/coastwatch/acspo/catalog_sst_acspo_avhrrgac.html

[Please acknowledge "NOAA CoastWatch/OceanWatch" when you use data from our site and cite the particular dataset DOI as appropriate.]

• Advanced Clear Sky Processor for Oceans (ACSPO) ftp://ftp.star.nesdis.noaa.gov/pub/sod/osb/aignatov/ACSPO/ (contains samples, Interface Control Document describing file contents, background ppt and other info).
• 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/
• 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/
• 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, and A. Heidinger, 2010: Clear-Sky Mask for ACSPO. JTech, 27, 1609-1623


(♦ - non-government website)

• 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, www.mdpi.com/2072-4292/8/4/315 ♦

(♦ - non-government website)