MODIS 500m spatial resolution ocean colour data

The monitoring of coastal and estuarine environments is becoming increasingly important due to the increase in anthropogenic pressures and the possible effects of climate change. A potentially valuable tool is high temporal and spatial resolution satellite ocean colour data. Typically ocean colour data are captured at a spatial resolution of 1km. However, NASA's Moderate Resolution Imaging Spectroradiometer (MODIS)-Terra and -Aqua can capture data at both 250m and 500m spatial resolutions and the existence of two sensors provides the possibility for multiple daily passes over a scene. These MODIS 250m and 500m bands were originally intended for remote sensing applications over the land, although more recently their potential for ocean colour has been highlighted.

Members of the PML remote sensing group have developed a method to automatically atmospherically correct the MODIS bands 3 and 4 which capture optical data at a spatial resolution of 500m and enables these data to be used for monitoring purposes. The approach provides a dynamic pixel by pixel atmospheric correction that allows the aerosol properties to vary across the scene. A method to determine chlorophyll-a concentration, from these MODIS 500m data has also been developed. MODIS 500m spatial resolution data are now being processed in near-real time for the Celtic Sea.

Figure 1 shows suspended particulate matter from the rivers Dart, Teign and Exe distributed along the English coast with the Kingsbridge estuary in the centre of the scene on 17 March 2003 12:45 UTC. The 1km scene, figure 1a, shows the suspended particulate matter distributed along the coast and around the Kingsbridge estuary with higher concentrations to the east of the scene. The increased resolution of the 500m scene (figure 1b) shows that the suspended matter forms a plume which is detached from the coastline, suggesting that it is not associated with the Kingsbridge estuary.

1km Scene 500m Scene
(a) 1km Scene (b) 500m Scene

Figure 1 Example LWN data (in mW cm-2 sr-1 μ m-1) on 17 March 2003 12:45 UTC; a) 1km LWN(551) displayed at the same spatial scale as, b) the 500m LWN(555) data.

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