ata processing and special sessions on key themes including water, land and atmosphere applications.
Olivier Arino, Head of Projects in ESA's Earth Observation Applications Department gave the Workshop an overview of projects being run by the Agency that use MERIS or similar instruments to attempt to develop operational services to the global community, responding to the requirements of key users. Work is already being done across a variety of fields such as carbon modelling, food security, marine pollution, fishery and snow mapping and desertification.
Ocean colour scene
As a pioneer in the field of ocean colour, Professor André Morel of the University of Pierre and Marie Curie in Paris has had a long association with MERIS. During the Workshop he co-chaired a splinter session on MERIS water products. Accurate measurements along signature wavebands means water contents can be known to a high degree of accuracy – from suspended sediments to living phytoplankton.
"Our expectations were very high for this instrument," said Morel. "The scientific community was waiting a long time. Now at last the products are routinely available for use by scientists. Overall the results we are getting seem very positive and reliable. The performance of the MERIS instrument is living up to the promise of its original design."
Accurately measuring ocean colour with MERIS presents a real technical challenge, particularly because only 1% of the top-of-atmosphere signal actually comes direct from ocean colour – the 99% comes from the atmosphere. To banish the effects of atmospheric distortion for ocean colour study meant extensive study of signal alteration – and almost by default this knowledge also enabled improved observation of atmospheric constituents.
Something in the air
"MERIS was not originally envisaged as an atmospheric sensor, but we have found it works very well as one," said Prof. Jan-Peter Muller of University College London. "For instance, we can detect surface and cloud top pressure up to an accuracy of 100 metres, the presence of aerosols and also water vapour concentration up to an accuracy of 3%, which represents unprecedented accuracy.
"Water vapour is highly variable in the atmosphere, and knowledge of its distribution would be very useful for forecasting rainfall. MERIS's revisit time of three days is too low for operational weather forecasting, but it raises the suggestion that a version of the instrument might be flown on future weather satellites."
Over solid ground, MERIS images provide information on land use and vegetation cover, and specific chlorophyll-linked spectral bands help quantify biomass concentration and condition.
Professor Jose Moreno of the University of Valencia detailed MERIS-related results from a July multi-spacecraft validation campaign carried out at the Barrax test site in La Mancha, Spain. The agricultural fields making up the site were characterised to a very high degree of detail, with more than 4000 ground samples taken, plus recordings of atmospheric conditions.
"Often you can have a good knowledge of the land surface corrections required but not the atmospheric corrections - or vice versa," said Moreno. "But with MERIS we have both, which means we can be more confident the data show what is really there.
"Being able to compare MERIS data with ESA's Proba micro-satellite was also useful. The main camera on Proba has four times the spectral bands on MERIS, and its resolution is 30 metres instead of 300 metres – so we could make out individual fields with Proba, to check them against what the larger-scale MERIS images were showing."
Since MERIS products became available in March 2003, Dr Cristina Rodríguez-Benito of Chile-based oceanographic company Mariscope Chilena has been using it to chart one very specific phenomenon: fish-killing algae blooms that threaten Chile's successful aquaculture industry.
"My interest is not only scientific research but also to focus this work on a direct application," said Rodríguez-Benito. "MERIS works better for the purpose of detecting algae blooms than comp