A robust band ratio technique for determining coloured dissolved organic matter in Lake Peipsi and Vortsjärv
Asuküll, Elar; Reinart, Anu; Ligi, Martin; Krista, Alikas
Tartu Observatory, ESTONIA

Remote sensing of water colour from space rests on the use of spectral bands providing radiometric information at a few selected wavelengths about the light backscattered from the upper layer of the water. As every object has its own spectral reflectance pattern it is possible to accentuate the occurrence of a particular material by combining different spectral bands. This so called band rationing is a robust and powerful technique used in the field remote sensing. Coloured dissolved organic matter (CDOM) is the main light absorbing fraction in many inland and coastal waters and also a very important environmental factor in global carbon cycle. Data from shallow and turbid Estonian lakes Vortsjärv (a_CDOM(442) - 2,3-10,4 (m^-1)) and Peipsi (a_CDOM(442) - 1,5-12,0 (m^-1)) will be analyzed with MERIS full resolution images from 2008 (42 images) along with in situ measurements from 2008-2011 (total of 407 samples). Although in water remote sensing band-ratio technique gives usually good results only in local scale and is therefore considered as case specific, the results will be compared to other similar available algorithms.