Mtci: the Meris Terrestrial Chlorophyll Index

The long wavelength edge of the major chlorophyll absorption feature in the spectrum of a vegetation canopy moves to longer wavelengths with an increase in chlorophyll content. The position of this red-edge has been used successfully to estimate, by remote sensing, the chlorophyll content of vegetation canopies. Techniques used to estimate this red-edge position (REP) have been designed for use on small volumes of continuous spectral data rather than the large volumes of discontinuous spectral data recorded by contemporary satellite spectrometers. Also, each technique produces a different value of REP from the same spectral data and REP values are relatively insensitive to chlorophyll content at high values of chlorophyll content. This paper reports on the design and preliminary evaluation of a surrogate REP index for use with spectral data recorded at the standard band settings of the Medium Resolution Imaging Spectrometer (MERIS). This index, termed the MERIS Terrestrial Chlorophyll Index (MTCI) was evaluated indirectly using model spectra, field spectra and MERIS data. It was easy to calculate (and so can be automated), was correlated strongly with REP and unlike REP, was sensitive to high values of chlorophyll content. Further evaluation of the MTCI is proposed, using both greenhouse and field data. Its utility for a regional scale application in southern Vietnam is also discussed.