NASA’s Physical Oceanography Distributed Active Archive Center (PO.DAAC) announced the public release of new NOAA GHRSST G18/ABI L2P/L3C v2.90 datasets from the new geostationary satellite, GOES-18 (G18). The G18 was launched on March 1, 2022, moved into the official West position @137.0W on June 6, 2022, and officially declared operational on Jan. 4, 2023. G18 replaces the previous GOES-West satellite, G17. G17 L2P/L3C datasets are available via the Earthdata catalog (L2P: https://doi.org/10.5067/GHG17-2PO71; L3C: https://doi.org/10.5067/GHG17-3UO71).
The G18 datasets are produced with the National Oceanic and Atmospheric Administration (NOAA) enterprise Advanced Clear Sky Processor for Ocean (ACSPO) v2.90 SST system, by the NOAA Center for Satellite Applications and Research (STAR). The datasets are formatted as netCDF-4, in compliance with the Group for High Resolution Sea Surface Temperature (GHRSST) Data Processing Specification version 2.0 (GDS2). Detailed information regarding the GHRSST Level 2P/3C products are available from the GHRSST mission website.
The L2P SST is produced in the instrument native swath projection with 2km/nadir spatial resolution. The L3C SST is the gridded (at 0.02-deg equal-angle projection) version of L2P. Both L2P and L3C are reported hourly, 24 granules per day, with a daily volume of 1.5 GB/day. The near real-time (NRT) data are updated hourly, with several hours latency. The NRT files are replaced with Delayed Mode (DM) files, with a latency of ~2-months. Filenames remain unchanged, and DM vs NRT can be identified by different time stamps and global attributes inside the files (MERRA instead of GFS for atmospheric profiles, and same day CMC L4 analyses in DM instead of one-day delayed in NRT processing).
ACSPO v2.90 enhancements and updates over the v2.70/2.71 (employed with G16 and G17, respectively) include:
- Improved clear-sky mask minimizes false alarms/over-screening in dynamic and coastal areas while reducing cloud leakages (in particular, residual cloud in clear/cloud transition zones).
- Significantly simplified NLSST formulation uses fewer ABI bands.
- Two thermal front layers added (location of fronts, and intensity in unit of kelvin/km).
- Improved SSES algorithm. SSES biases and standard deviations are now more representative of the retrieval uncertainties, rather than skin-bulk differences.
- Improved ACSPO processor is cleaner and better organized, with some bugs fixed and potential sources of instabilities mitigated.
- Last two bits in the l2p_flags are redefined. bit15 is set to 0 for high-quality SSTs (QL=15), and to 1 if QL<5. Bit16 is set to 0 when there is valid water in pixel (ocean, lake, river); and to 1 for (land, ice, or invalid).
At the time of this announcement, the G18 L2P/L3C data holdings in PO.DAAC cover from July 11, 2023, onward and the record will be extended to Jun 7, 2022 by September 2023. Both datasets are described and discoverable via the Earthdata catalog, and accessible via the Cloud OPeNDAP and Harmony API services. We recommend users to download the data with the podaac-data-subscriber python tool.
Reference
Gladkova, I., A. Ignatov, A. Semenov (2022). Analysis of ABI bands and regressors in the ACSPO GEO NLSST algorithm, Proc. SPIE, Ocean Sensing and Monitoring XIV; 1211804, https://doi.org/10.1117/12.2620058.
If you have questions, please contact PO.DAAC user services or visit PO.DAAC on Earthdata Forum.