Satellite Ocean Observing System

Introduction

The AIMS Remote Sensing Atlas (atlas) is a web based facility that provides access to ocean related data products derived from satellite remote sensing measurements.

There are three products available, with more to be added in the future. The current products are:

• Sea Surface Temperature (SST);
• Chlorophyll a (Chl a); and
• Diffuse attenuation coefficient at 490nm (K490).

The data are presented as a daily "snapshot" for the region bounded by 7 deg S to 28 deg S latitude and 142 deg E to 158 deg E longitude. The atlas provides the abililty to view, query and download (with limitations) the data for these products.

Please read the following caveats before applying data downloaded from this site.

Disclaimer

Care in interpretation

Users of this data should be aware that it is experimental and significant errors may exist. It is being made available for educational and research purposes. In particular some of the data may have errors due to undetected cloud and other aerosols. This may produce reductions in the apparent SST.

SST is measuring only the skin layer (<1mm) and is a spatial average of over 1km. Algorithms are dependent upon wind speed and the relationship with the so called bulk water temperatures that are usually referenced to be at 1m below the surface. So care needs to be taken when comparing with other in situ measurements.

Ocean colour in shallow coastal regions can see the bottom and may not indicate true water column colour. The Chl a algorithms are designed for open ocean waters only. Nevertheless significant features shown in the data allow the complexity of coastal and ocean waters to be revealed.

Data Sources

The satellite data used to derive the current products were received at AIMS using the local HRPT direct broadcast receiving station. Future products may include data obtained from other sources.

The SST data is derived from the AVHRR/2 or AVHRR/3 sensor on board the NOAA series of satellites. The Chl a and K490 products are both derived from the SeaWiFS sensor on board the Seastar or Orbview 2 satellite.

The NOAA satellites are operated by the US National Oceanic and Atmospheric Administration. The data from these platforms are freely available to anyone with a receiving system and there is no limitation on data distribution.

The Seastar satellite is operated by GeoEye (formerly Orbimage Inc.) and the distribution of data from this platform is restricted by a research agreement with that company.

Product Details

The SST product is based only on the overpasses from the satellite NOAA designates as the "primary PM" satellite. This refers to the satellite with the best current performance (usually the most recently launched of those still operating) which has the daylight part of its orbit occurring in the local solar afternoon.

This is significant in that recent research has shown that these "afternoon passes" can give a biased estimate of the SST due to diurnal variation in surface temperature. Future improvements planned include using the morning and night-time overpasses.

The SST calculation is performed using a method very similar to that used for the NOAA Coastwatch Region SST and use the NOAA/AVHRR operational SST algorithms and coefficients  

Further details of the processing may be obtained from the authors.

The Chl a and K490 (ocean colour products) have been produced using the SeaDAS software suite which gives equivalent results to the NASA operational products.

Extensive information about these products and other derived from the SeaWiFS and MODIS sensors may be found at the NASA GSFC Ocean Colour web site.

A brief description of the products and links to further information may be found at:
Chl a and K490

October 31, 2007