Introduction

Satellite SST observations contribute to an understanding of regional variability and global climate change and permit the visualization of a wide variety of oceanic flows. These observations are important for the following reasons. First, because the upper 3 m of the water column has about the same heat capacity and the upper 10 m has about the same mass as the overlying column of atmosphere, the upper ocean moderates the global climate system where SST is proportional to the upper ocean heat storage (Gill, 1982). SST varies from about −1.8 °C near the edge of the polar sea ice to about 30 °C near the equator. Second, the spatial and temporal distributions of the atmospheric fluxes of water vapor and heat are functions of surface temperature. Third, the patterns of surface temperature gradients associated with current systems, eddies, jets and upwelling regions make these processes visible in SST imagery. Given the importance of SST to the global heat budget, the Global Climate Observing System (GCOS, 2011) describes SST as an essential climate variable.

In 1981, satellite infrared observations of SST began with the launch of the AVHRR/2 on NOAA-7, so that there now exist three decades of satellite SSTs. These SST observations contribute to studies of multiyear global climate change and to short-time-period regional support of fisheries, ship routing, hurricane forecasting, and delineation of ocean fronts, upwelling regions, equatorial jets and ocean eddies (Walton et al., 1998; Gentemann et al., 2009). For numerical weather prediction (NWP) models, SST serves as a critical surface boundary condition. The applications of SST data sets range from regional studies of upwelling at the eastern boundaries of the ocean to large-scale studies of the variability associated with the phenomenon of El Niño Southern Oscillation (ENSO) in the equatorial Pacific.