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Comparison of GOES and POES SST Against In-Situ SST Validations for NOAA CoastWatch regions

  All Regions | West Coast | East Coast | Hawaii | Gulf of Mexico

NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) produces two main types of POES related SST products; i.e., global SST and CoastWatch SST. Operational AVHRR multichannel SST algorithms have been used to generate global SST measurements at NESDIS since November 1981. The global SST suite of products are generated from AVHRR Global Area Coverage (GAC) 4 km data recorded on-board the POES satellites and downlinked to NESDIS acquisition stations at Wallops Station, Virginia and Fairbanks, Alaska. Global SST measurements are produced at 8 km resolution with variable spacing from 8 km to 25 km in cloud-free areas twice per day from each of the two operational POES satellites.

POES CoastWatch sea surface temperature (SST) products are generated from a different data stream, the Advanced Very High Resolution Radiometer (AVHRR) High Resolution Picture Transmission (HRPT) data, broadcast continuously by the National Oceanic and Atmospheric Administration (NOAA) series of Polar-orbiting Operational Environmental Satellites (POES) satellites, which include NOAA-17 and -18. These data are received at the Wallops station for the East Coast, Great Lakes, and Gulf of Mexico CoastWatch Regional Nodes. The West Coast, Hawaii, and Alaska CoastWatch Regional Nodes all have their own HRPT reception stations and acquire their own data. The HRPT data have a resolution of 1.1 km at nadir and are mapped to almost full resolution in the production of CoastWatch AVHRR visible, infrared, SST images, cloud masks, etc. Currently, NOAA CoastWatch SST products are generated using the Seaspace's TeraScan software. TeraScan software allows these image products to be automatically navigated within one image pixel accuracy.

NOAA uses the Nonlinear SST (NLSST) and Multi-channel SST (MCSST) algorithms to generate CoastWatch SST products (Walton et al. 1998; Li et al. 2001a, b). The algorithm coefficients are derived based on a regression analysis of the satellite derived SST and in situ SST measurements made by global drifting buoys. The form of the POES CoastWatch equation is:

where: MCSST is given by:

where, T11 and T12 are the AVHRR 11 and 12 µm channel temperatures (K); θ is the satellite zenith angle; NLSST and MCSST are the SST values derived using non-linear and linear multi-channel SST retrieval algorithms, respectively (°C); ai and bi (i=1...4) are calculated using a regression method.

The POES CoastWatch SST equations differ from the global SST (GAC) equations in three respects:

  • The CoastWatch equations use the MCSST value in the non-linear term rather than an a priori SST estimate obtained from an analysis of past satellite SST data. This means that there is somewhat more noise in the CoastWatch observations. Both the global operation and CoastWatch constrain the value of the a priori SST or the MCSST to the range 0 oC to 28 oC.
  • In the Great Lakes, the MCSST value is used as the final SST value during the day; i.e., a linear equation is used as the operational equation rather than a non-linear equation.
  • The NLSST split-window equation is used for CoastWatch rather than the triple-window equation (employing all three infrared channels) which is used in the global operation.
  • To access the accuracy of the CoastWatch products and monitor the satellite AVHRR instrument performance, the POES CoastWatch SST is validated with the in situ moored buoy measurements from National Data Buoy Center in the coastal waters of US EastCoast, Gulf of Mexico, WestCoast, and Hawaii regions. The validation statistics are released on a monthly basis. By comparioson, the validation of POES CoastWatch SST and the one of GOES CoastWatch SST against buoy SST from ship, drifting and moored are presented here:

    Click on the desired area on the images below to view results for individual CoastWatch region(white box), and outside of white boxes for all regions together