TORMS

Total Ozone Retrieval Using MERIS (TORMS) in view of Sentinel-3 is a project that proposes an innovative way to assess total column of ozone from visible Top Of Atmosphere (TOA) reflectance and from assumption on the free absorption TOA spectrum.

The method assumes that the TOA reflectance spectrum in the absence of gaseous absorption can be modelled by a third order polynomial. TCO is then retrieved by making use of the difference between this polynomial calculated from bands number 1, 2, 10, 12 and 13, and the measured reflectance in band number 3, 4, 5, 6, 7 and 8 where ozone absorbs (it includes Chappuis bands). This method has been applied to the full MERIS archive and MERIS TCOs have been compared to those retrieved more classically from the UV nadir sensor GOME-2A. The method is valid over bright and spectrally white surface such as snow/ice surfaces and optically thick clouds. The TCOs from MERIS and GOME-2A agree generally well over Antarctica, while MERIS tends to underestimate TCOs elsewhere. MERIS TCOs have also been compared to ground measurements and show a good correlation (bias and root mean square error of about 4 and 20 DU, respectively). Thanks to its high spatial and temporal resolution, this product is of prime interest to study and monitor dynamics of the ozone hole around the South Pole.

Monthly composite of Total Column Ozone (in DU) from MERIS for November 2008
Daily Total Column Ozone animation from October to December 2008

More information on a poster presented at Living Planet Symposium 2016 and on the paper conference.

Funder: ESA
Duration: 2015-2016
Contact at Hygeos: Dominique Jolivet