as dynamical, coupled ocean–atmosphere models. Increasing use of real-time and
historic SST data in models, in conjunction with other data sources, is helping
address more complex ecological and management problems.
12.1 Introduction
12.1.1 Infrared and Microwave Sensors
Sea surface temperature (SST) is a key measurement routinely made by satellite
thermal infrared (TIR) and passive microwave (PMW) radiometers, in situ moored
and drifting buoys, and ships of opportunity. These measurements are used to
create daily spatially-complete global maps of SST that are used for ocean forecasts, weather prediction, coastal applications such as coral reef management and
fisheries, and also for research by oceanography, meteorology, and climate
scientists.
TIR sensors have been deployed on earth observing satellites for over 30 years
and TIR-derived SST measurements are available in near real-time from a wide
variety of satellite missions (Table 11.2). Of these, the most commonly used are
the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA Polarorbiting Operational Environmental Satellites and the Moderate Resolution
Imaging Spectroradiometer (MODIS) aboard the NASA Earth Observing System
Terra and Aqua Satellites. TIR sensors on polar-orbiting satellites have a characteristic spatial resolution of 1.1 km (at nadir) with quasi-global coverage on a
daily basis. TIR satellite retrievals are derived from radiometric observations in
two distinct wavebands located at *4 and 10–13 lm. The 4 lm channel is more
sensitive to SST but is used only for night-time measurements because of the
relatively strong reflection of solar irradiation at this wavelength. SST retrievals at
10–13 lm are used for day and night-time measurements. Both bands are sensitive
to the presence of clouds and scattering by aerosols and atmospheric water vapor,
hence TIR-derived SST measurements require atmospheric correction of the
retrieved signal and can only be made for cloud-free pixels. The on-board calibration of TIR sensors (e.g., Corlett et al. 2006) is therefore supplemented with
vicarious calibration in SST retrieval algorithms that compensate for the atmospheric attenuation of water leaving radiances using in situ SST measurements
(e.g., Kilpatrick et al. 2001; Zhang et al. 2009). Geostationary satellites carry
radiometers with TIR channels similar to the AVHRR. While their spatial resolution is coarser (*5 km), geostationary satellites sample at a higher temporal
resolution (repeat acquisitions *30 min), enabling the measurement of SST over
ocean regions experiencing ephemeral cloud.
Prior to 1998, SST retrievals were only available globally from TIR sensors, but
the launch of the TRMM (Tropical Rainfall Measuring Mission) Microwave
314
S. J. Weeks et al.
historic SST data in models, in conjunction with other data sources, is helping
address more complex ecological and management problems.
12.1 Introduction
12.1.1 Infrared and Microwave Sensors
Sea surface temperature (SST) is a key measurement routinely made by satellite
thermal infrared (TIR) and passive microwave (PMW) radiometers, in situ moored
and drifting buoys, and ships of opportunity. These measurements are used to
create daily spatially-complete global maps of SST that are used for ocean forecasts, weather prediction, coastal applications such as coral reef management and
fisheries, and also for research by oceanography, meteorology, and climate
scientists.
TIR sensors have been deployed on earth observing satellites for over 30 years
and TIR-derived SST measurements are available in near real-time from a wide
variety of satellite missions (Table 11.2). Of these, the most commonly used are
the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA Polarorbiting Operational Environmental Satellites and the Moderate Resolution
Imaging Spectroradiometer (MODIS) aboard the NASA Earth Observing System
Terra and Aqua Satellites. TIR sensors on polar-orbiting satellites have a characteristic spatial resolution of 1.1 km (at nadir) with quasi-global coverage on a
daily basis. TIR satellite retrievals are derived from radiometric observations in
two distinct wavebands located at *4 and 10–13 lm. The 4 lm channel is more
sensitive to SST but is used only for night-time measurements because of the
relatively strong reflection of solar irradiation at this wavelength. SST retrievals at
10–13 lm are used for day and night-time measurements. Both bands are sensitive
to the presence of clouds and scattering by aerosols and atmospheric water vapor,
hence TIR-derived SST measurements require atmospheric correction of the
retrieved signal and can only be made for cloud-free pixels. The on-board calibration of TIR sensors (e.g., Corlett et al. 2006) is therefore supplemented with
vicarious calibration in SST retrieval algorithms that compensate for the atmospheric attenuation of water leaving radiances using in situ SST measurements
(e.g., Kilpatrick et al. 2001; Zhang et al. 2009). Geostationary satellites carry
radiometers with TIR channels similar to the AVHRR. While their spatial resolution is coarser (*5 km), geostationary satellites sample at a higher temporal
resolution (repeat acquisitions *30 min), enabling the measurement of SST over
ocean regions experiencing ephemeral cloud.
Prior to 1998, SST retrievals were only available globally from TIR sensors, but
the launch of the TRMM (Tropical Rainfall Measuring Mission) Microwave
314
S. J. Weeks et al.