Satellite Eye for Galathea 3 at DTU

Satellit observations of SST

At the time of writing, several satellites are in orbit carrying instruments that observe SST. Most of these observations are being collected by the Satellite Eye project and are combined to daily high-resolution images of satellite sea surface temperature (SST). The spatial resolution and the temporal resolution from the satellite observations vary among instruments.

 Table 1: Overview of the sources for high-resolution satellite SST observations is listed. IR is infrared and MB is microwave.

The data are collected by use of the Sea and Sea-ice SAF (Satellite Application Facility) belonging to EUMETSAT (Satellite operator for the European Meteorological Institute).

As the infrared observations are limited by cloud cover and the microwave observations are of rather low spatial resolution, an interpolation scheme for the data has been applied in order to obtain high-resolution SST maps without gaps.

Observations listed in the table therefore have been collected by DMI and a method called objective analysis has been applied. This method uses statistics to fill out gaps and provide and interpolated SST map each data with a spatial resolution at around 5 km.
The infrared radiation and the microwave radiation originates from the upper millimeter or less of the sea surface, but the sea surface temperatures presented are corrected such that they represent the temperature of the upper one meter. This has been done by inter-comparing vast amounts of observations from ships with satellite observations.

Two maps of satellite SST are shown from 24 February 2007. The first map covers the Indian Ocean. It is clear that the ocean is warm near the Equator and cool near Antarctica. The other map covers the ocean along the west coast of South America. It can be noted that the ocean is rather cool along the coastline compared to further offshore. The cool water stems from upwelling of cold water from the bottom to the surface layer. The Galathea 3 expedition is doing investigations in the cool water masses. The upwelling is associated with input of nutrients from the bottom to the ocean surface layer that feed phytoplankton and the rest of the marine food web (fishes etc.).

Animations of satellite SST can be viewed in Google Earth from http://galathea.oersted.dtu.dk/GE_animation.html and regionally at http://galathea.oersted.dtu.dk/SST_e.html