1,721,150 research outputs found
Relationship between herbicide concentration during the 1960s and 1970s and the contemporary MERIS Terrestrial Chlorophyll Index (MTCI) for southern Vietnam
No full textLarge concentrations of herbicide were sprayed onto the forests of southern Vietnam in the 1960s and early 1970s. Over 30 years later, many of these contaminated forests have regained full canopy cover, albeit with reduced chlorophyll content. The European Space Agency produces an operational product for the estimation of terrestrial chlorophyll content over large areas of terrain. This product uses data recorded by the Medium Resolution Imaging Spectrometer (MERIS) on Envisat and is called the MERIS Terrestrial Chlorophyll Index (MERIS). The relationship between historical levels of herbicide contamination and contemporary MTCI was strong (R50.86) and negative, with high levels of herbicide contamination being associated (via low levels of chlorophyll concentration) with low levels of MTCI. This is the first published study to demonstrate a relationship between MTCI and a surrogate for chlorophyll content. The next stage of this research is to build on the strength ofthis relationship and use contemporary MTCI to estimate historical herbicide levels during the 1960s and 1970s across southern Vietnam
Assessing gross primary productivity in North American ecosystems using a chlorophyll-based vegetation index
No full textThe MERIS Terrestrial Chlorophyll Index
No full textThe 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 indirect 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 using model spectra, field spectra and MERIS data. It was easy to calculate (and so can be automated), was correlated strongly with REP but unlike REP was sensitive to high values of chlorophyll content. As a result this index became an official MERIS level-2 product of the European Space Agency in March 2004. Further direct evaluation of the MTCI is proposed, using both greenhouse and field data
Discriminating and mapping the c3 and c4 composition of grasslands in the northern Great Plains, USA
No full textThere is uncertainty about the extent and distribution of grasslands following the C3 and C4 photosynthetic pathways. Since these grasses have an asynchronous seasonal profile it should be possible to estimate and map the C3–C4 composition of grasslands from multi-temporal remote sensing imagery. This potential was evaluated using 30 weekly composite MERIS MTCI images for South Dakota, USA. Derived relationships between the remotely sensed response and composition of grasslands were significant, with R2 0.6. It also appears possible to map broad classes of grassland composition, with a three class (high, medium and low C3 cover) classification having an accuracy of 77.8%
Evaluation of the MERIS Terrestrial Chlorophyll Index (MTCI)
No full textThe MEdium Resolution Imaging Spectrometer
(MERIS), one of the payloads on Envisat, has fine spectral
resolution, moderate spatial resolution and a three day repeat
cycle. This makes MERIS a potentially valuable sensor for the
measurement and monitoring of terrestrial environments at
regional to global scales. The red edge, which results from an
abrupt change in reflectance in red and near-infrared
wavelength has a location that is related directly to the
chlorophyll content of vegetation. A new index called the MERIS
terrestrial chlorophyll index (MTCI) uses data in three red/NIR
wavebands centred at 681.25nm, 705nm and 753.75nm (bands 8,
9 and 10 in the MERIS standard band setting). The MTCI is easy
to calculate and can be automated. Preliminary indirect
evaluation using model, field and MERIS data suggested its
sensitivity, to notably high values of chlorophyll content and its
limited sensitivity to spatial resolution or atmospheric effects. As
a result this index is now a standard level-2 product of the
European Space Agency.
For direct MTCI evaluation two different approaches were used.
First, the MTCI/chlorophyll content relationship were
determined using a chlorophyll content surrogate for sites in
southern Vietnam and second, the MTCI/chlorophyll
relationship was determined using actual chlorophyll content for
sites in the New Forest, UK and for plots in the greenhouse.
Forests in southern Vietnam were contaminated heavily with
Agent Orange during the Vietnam War. The contamination level
was so high that it led to a long term decrease in chlorophyll
content within forests that have long since regained full canopy
cover. In this approach the amount of Agent Orange dropped on
to the forest between 1965 and 1971 was used as a surrogate
(inverse) for contemporary chlorophyll content and was related
to current MTCI at selected forest sites. The resulting
relationship was negative. Further per pixel investigation of the
MTCI/Agent Orange concentration relationship is under way for
large forest regions. In the second approach MTCI was related
directly to chlorophyll content at two scales and the initial
resulting relationships were positive. Further plans involve the
evaluation of the MTCI at local, regional and eventually global
scales
Evaluation of the MERIS Terrestrial Chlorophyll Index
No full textThe medium resolution imaging spectrometer (MERIS), one of the payloads on Envisat, has fine spectral resolution, moderate spatial resolution and a three day repeat cycle. This makes MERIS a potentially valuable sensor for the measurement and monitoring of terrestrial environments at regional to global scales. The red edge, which results from an abrupt change in reflectance in red and near-infrared wavelength has a location that is related directly to the chlorophyll content of vegetation. A new index called the MERIS terrestrial chlorophyll index (MTCI) uses data in three red/NIR wavebands centred at 681.25 nm, 705 nm and 753.75 nm (bands 8, 9 and 10 in the MERIS standard band setting). The MTCI is easy to calculate and can be automated. Preliminary indirect evaluation using model, field and MERIS data suggested its sensitivity, to notably high values of chlorophyll content and its limited sensitivity to spatial resolution or atmospheric effects. As a result this index is now a standard level-2 product of the European Space Agency. For direct MTCI evaluation two different approaches were used. First, the MTCI/chlorophyll content relationship were determined using a chlorophyll content surrogate for sites in southern Vietnam and second, the MTCI/chlorophyll relationship was determined using actual chlorophyll content for sites in the New Forest, UK and for plots in the greenhouse. Forests in southern Vietnam were contaminated heavily with Agent Orange during the Vietnam War. The contamination level was so high that it led to a long term decrease in chlorophyll content within forests that have long since regained full canopy cover. In this approach the amount of Agent Orange dropped on to the forest between 1965 and 1971 was used as a surrogate (inverse) for contemporary chlorophyll content and was related to current MTCI at selected forest sites. The resulting relationship was negative. Further per pixel investigation of the MTCI/Agent Orange concentration relationship is under way for large forest regions. In the second approach MTCI was related directly to chlorophyll content at two scales and the initial resulting relationships were positive. Further plans involve the evaluation of the MTCI at local, regional and eventually global scales
Evaluating the impact of Indian Ocean tsunami on agricultural yield in Hambantota Province, Sri Lanka
No full text- …
