254
H.M. Beggs
15.3 Level 3 Composite SST Products
Level 2 (single orbit) SST products can be combined to produce either a singlesensor or multiple-sensor, gridded, “level 3” SST product. Table 15.2 gives a few
examples of operational level 3 composite SST products formed from level 2 files
of IR SST (GOES-11, GOES-12, MSG-9, MTSAT-1R, MODIS and AVHRR) that
are used in operational applications.
These applications include fisheries management and protection of endangered
species (e.g. TurtleWatch, Howell et al., 2008), hindcasting and nowcasting of coral
bleaching and weather forecasting.
15.4 Level 4 SST Analyses
Gap-free, “level 4”, analyses of satellite level 2 and in-situ SST are produced operationally at various oceanographic and meteorological agencies around the world
using the method of optimal interpolation (OI) (e.g. Smith et al., 1991). These
SST analyses provide sea surface boundary forcing in atmospheric and ocean models, and are used as a constraint to observations in modelling of the upper ocean
circulation. Accurate SST fields are essential in computing different climate variables, such as heat transfer in ocean-atmosphere coupled systems and surface pCO 2
(Vinogradova et al., 2009).
Over the last 10 years or so, progress in the real-time analysis of satellite SST
has been made possible by the following developments:
• Dramatic improvement in the quality and quantity of IR SST retrievals from
AVHRR instruments aboard POES satellites
• Arrival of new sources of highly accurate IR SST (e.g. AATSR, errors from
0.16 ◦ C (O’Carroll et al., 2008))
• Arrival of new sources of accurate microwave SST (e.g. AMSR-E)
• Progress in facilitating access and exchange of data through international cooperation such as implemented by GHRSST-PP.
Infrared SST observations from AATSR, AVHRR and MODIS provide accurate
estimates of SST at high resolution (~1 km) within the ocean cool skin (~10–20 μm
depth; SSTskin), but only over cloud-free regions. Microwave observations from
the AMSR-E instrument on Aqua provide SST observations in the subskin region
(~1 mm depth; SSTsubskin), at coarser resolution (~25 km) but with the advantage
of being able to measure SST through cloud (although not rain). In addition, IR SST
observations from geostationary satellites provide up to half-hourly observations of
SSTskinat ~5 km resolution in cloud-free regions, with the advantage of frequent
temporal sampling enabling the measurement of SST over ocean regions experiencing ephemeral cloud. A summary of the various definitions of SST is presented in
Table 15.3.
H.M. Beggs
15.3 Level 3 Composite SST Products
Level 2 (single orbit) SST products can be combined to produce either a singlesensor or multiple-sensor, gridded, “level 3” SST product. Table 15.2 gives a few
examples of operational level 3 composite SST products formed from level 2 files
of IR SST (GOES-11, GOES-12, MSG-9, MTSAT-1R, MODIS and AVHRR) that
are used in operational applications.
These applications include fisheries management and protection of endangered
species (e.g. TurtleWatch, Howell et al., 2008), hindcasting and nowcasting of coral
bleaching and weather forecasting.
15.4 Level 4 SST Analyses
Gap-free, “level 4”, analyses of satellite level 2 and in-situ SST are produced operationally at various oceanographic and meteorological agencies around the world
using the method of optimal interpolation (OI) (e.g. Smith et al., 1991). These
SST analyses provide sea surface boundary forcing in atmospheric and ocean models, and are used as a constraint to observations in modelling of the upper ocean
circulation. Accurate SST fields are essential in computing different climate variables, such as heat transfer in ocean-atmosphere coupled systems and surface pCO 2
(Vinogradova et al., 2009).
Over the last 10 years or so, progress in the real-time analysis of satellite SST
has been made possible by the following developments:
• Dramatic improvement in the quality and quantity of IR SST retrievals from
AVHRR instruments aboard POES satellites
• Arrival of new sources of highly accurate IR SST (e.g. AATSR, errors from
0.16 ◦ C (O’Carroll et al., 2008))
• Arrival of new sources of accurate microwave SST (e.g. AMSR-E)
• Progress in facilitating access and exchange of data through international cooperation such as implemented by GHRSST-PP.
Infrared SST observations from AATSR, AVHRR and MODIS provide accurate
estimates of SST at high resolution (~1 km) within the ocean cool skin (~10–20 μm
depth; SSTskin), but only over cloud-free regions. Microwave observations from
the AMSR-E instrument on Aqua provide SST observations in the subskin region
(~1 mm depth; SSTsubskin), at coarser resolution (~25 km) but with the advantage
of being able to measure SST through cloud (although not rain). In addition, IR SST
observations from geostationary satellites provide up to half-hourly observations of
SSTskinat ~5 km resolution in cloud-free regions, with the advantage of frequent
temporal sampling enabling the measurement of SST over ocean regions experiencing ephemeral cloud. A summary of the various definitions of SST is presented in
Table 15.3.