Satellite-derived sea surface temperatures from the AVHRR for the Vancouver Island Coastal Region

Abstract

In mid-May 1994 Royal Roads Military College (Victoria, BC.) established a remote sensing facility capable of acquiring data from the NOAA series of polar orbiting satellites and began to collect and archive Advanced Very High Resolution Radiometer (AVHRR) data covering the Pacific coast. This thesis presents an overview of the collection and archiving rocedures used in this local receiving site. To demonstrate the value of AVHRR data for assessing oceanographic features within the coastal waters of Vancouver Island, a time series of SST images derived using the NOAA/NESDIS Multi-Channel Sea Surface Temperature (MCSST) algorithm (1993) is presented. Linear correlation analysis indicates correlation coefficients of 0.88-0.94 between satellite-derived sea surface temperatures and in situ water temperatures measured by a series of offshore buoys. However, temperature biases of 0.2°C, with RMS errors of 1.3-1.5°C suggests the desirability of generating a regional MCSST algorithm for the Vancouver Island coastal region. The time series of SST images provides a comprehensive view of oceanographic processes in the coastal waters of Vancouver Island and indicates a seasonal current variability with meandering and eddy-spawning characteristics. Sea surface temperature fronts mirror coastal bathymetric features to depths between 200-500 m and the offshore summer current structure suggests the influence of canyons in the 500 m isobath that serve as a triggering mechanism for pronounced meandering. Juan de Fuca Strait, an estuary that provides a freshwater influence to the coastal region, demonstrates an across-strait temperature difference associated with a rotationally influenced (Coriolis) estuarine flow and definable sea surface temperature fronts due to tidally induced mixing and topographic features that separate the strait into two varying temperature regimes. Furthermore, numerous images provide evidence of the Vancouver Island Coastal Current (VICC) and its appearance supported the influence of a buoyant plume of freshwater from Juan de Fuca Strait which serves as a probable forcing mechanism. The final chapter presents a number of possible future directions for the AVHRR data collected from this local receiving site and applications within the coastal oceanographic environment for remotely sensed sea surface temperature imagery.