TY - JOUR
T1 - Validation of MERIS water quality products in Murchison Bay, Lake Victoria - Preliminary results
AU - Okullo, W.
AU - Hamre, B.
AU - Frette, O.
AU - Stamnes, J. J.
AU - Sorensen, K.
AU - Ssenyonga, T.
AU - Hokedal, J.
AU - Stamnes, K.
AU - Steigen, A.
PY - 2011/10
Y1 - 2011/10
N2 - As a step forward to validating the retrieval algorithm associated with the MERIS (Medium Resolution Imaging Spectrometer) sensor onboard the European Space Agency's ENVISAT satellite, we compare scaling factors for apig(442) (pigment absorption coefficient at 442 nm) versus chl-a concentration, and for bp(440) (scattering coefficient for particles at 440 nm) versus TSM (total suspended matter) concentration, as well as in situ measurements of chl-a and TSM concentrations in Murchison Bay, Lake Victoria, with MERIS level 2 products. Our comparisons show that MERIS chl-a data products underestimate the in situ chl-a concentration by a factor of about 0.6, and that MERIS level 2 products overestimate the in situ TSM concentration and the yellow substance absorption coefficient by a factor of about 2. Application of a local inherent optical property (IOP) scaling factor improves the retrieval provided by MERIS level 2 products. The MERIS level 2 products also underestimate the water-leaving reflectance. These discrepancies between retrievals from MERIS data and in situ measurements are due to the current imperfect atmospheric correction algorithm for inland waters. Therefore, a need arises to develop site-specific bio-optical models and to improve existing MERIS retrieval algorithms.
AB - As a step forward to validating the retrieval algorithm associated with the MERIS (Medium Resolution Imaging Spectrometer) sensor onboard the European Space Agency's ENVISAT satellite, we compare scaling factors for apig(442) (pigment absorption coefficient at 442 nm) versus chl-a concentration, and for bp(440) (scattering coefficient for particles at 440 nm) versus TSM (total suspended matter) concentration, as well as in situ measurements of chl-a and TSM concentrations in Murchison Bay, Lake Victoria, with MERIS level 2 products. Our comparisons show that MERIS chl-a data products underestimate the in situ chl-a concentration by a factor of about 0.6, and that MERIS level 2 products overestimate the in situ TSM concentration and the yellow substance absorption coefficient by a factor of about 2. Application of a local inherent optical property (IOP) scaling factor improves the retrieval provided by MERIS level 2 products. The MERIS level 2 products also underestimate the water-leaving reflectance. These discrepancies between retrievals from MERIS data and in situ measurements are due to the current imperfect atmospheric correction algorithm for inland waters. Therefore, a need arises to develop site-specific bio-optical models and to improve existing MERIS retrieval algorithms.
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U2 - 10.1080/01431161.2010.506895
DO - 10.1080/01431161.2010.506895
M3 - Article
AN - SCOPUS:80053111765
SN - 0143-1161
VL - 32
SP - 5541
EP - 5563
JO - International Journal of Remote Sensing
JF - International Journal of Remote Sensing
IS - 19
ER -