EAMNet Sea Surface Temperature - 1km

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Summary

Providers: Plymouth Marine Laboratory Prospect Place Plymouth PL1 3DH UK &
Department of Oceanography University of Cape Town, Rondebosch, Cape Town, South Africa, 7701

Contact person: Steve Groom, Send email

Contact for production: NEODAAS Helpdesk Send mail

Algorithm development: NASA (MODIS); ESA (MERIS), PML/UCT for mapping

Sea Surface Temperation (SST) is the near surface 'bulk' temperature of the water mass. Its values range from ~-3 °C to ~3 °C with units °Celsius. It is used for distinguishing betwen different water masses: temperature can show features like fronts, eddies, coastal upwelling, currents and mixing. Temperature also mediates biological processes so is an input to algorithms to compute, for example, phytoplankton primary production.

Data Portal: EAMNet

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Platform & processing

The NASA Aqua MODIS SST product is ~1.1km resolution at nadir and available from 2002 to the present . During the day time SST is computed with the longwave SST algorithm (Brown and Minnett (1999) and Minnett et al. (2003)) from MODIS bands 31 and 32 (11 and 12 um) with an initial "guess" at SST from the Reynolds OISST and the product called "SST"; during the night the shortwave SST algorithm uses MODIS bands 22 and 23 (3.959 and 4.050 um) and the product called "SST". NASA data are processed to level 2 using NASA specific software (see http://oceancolor.gsfc.nasa.gov/DOCS/modis_sst/). The user version of the processing software is called SEADAS and is available at http://oceancolor.gsfc.nasa.gov/seadas/.

Algorithm

The shortwave and longwave MODIS SST algorithms use coefficients that "are derived andcontinuously verified by RSMAS based on match-ups between the satellite retrievals of brightness temperature and field measurements of sea surface temperature." (http://oceancolor.gsfc.nasa.gov/DOCS/modis_sst/). The main data inputs are MODIS brightness temperature data at ~1.1 km resolution. The algorithm changes depending on the processing version - need to see latest information from NASA and ESA. See http://oceancolor.gsfc.nasa.gov/DOCS/modis_sst/.

Product uncertainties

See references. Cloud cover limits coverage of the sea-surface; during daytime superficial surface heating can mask SST.

The SST algorithms are constructed by the US Rosenstiel School of Marine and Atmospheric Sciences (RSMAS) based on match-ups between the satellite retrievals of brightness temperature and field measurements of sea surface temperature. As currently implemented, these coefficients can be time-dependent. (http://oceancolor.gsfc.nasa.gov/DOCS/modis_sst/).

Product dissemination

Data at 1.1 km resolution are not distributed via GEONETCast, but lower resolution (~4 km) data are provided through the OSI-SAF.

The basic data are distributed by Internet by NASA respectively, at various levels of processing. The DevCoCast produced data are also distributed via the internet.The typical delay of product is a minimum of 6 hrs from acquisition of data by NASA. Products from are delivered on best effort basis only.

See references. Composites are produced on day i for the period i-8 to i-1. Fully operational.

Product validation

Data characteristics

The area covered at 1.1 km depends on the region.

Individual overpasses give an instantaneous "snapshot" typically once per day over equatorial region(for MODIS) and every two days (for MERIS)

Data is presented using the Mercator projection.

Notes

When the MODIS processing changes the archive is also usually reprocessed so archives should be consistent.

Useful references:

Brown, O.B., and P.J. Minnett, 1999, MODIS Infrared Sea Surface Temperature Algorithm Theoretical Basis Document, Ver 2.0, http://modis.gsfc.nasa.gov/data/atbd/atbd_mod25.pdf

Kumar, A., P. J. Minnett, G. Podestà and R. H. Evans, 2003. Error characteristics of the atmospheric correction algorithms used i retrieval of sea surface temperatures from infrared satellite measurements: global and regional aspects. Journal of the Atmospheric Sciences, 60, 575-585.

Walton, C.C., W. G. Pichel, and J.F. Sapper, 1998, The development and operational application of nonlinear algorithms for the measurement of sea surface temperatures with the NOAA polar-orbiting environmental satellites, J. Geophysical Research, 103: (C12) 27999-28012