Modified Chlorophyll Absorption Ratio Index Improved (MCARI2)

Description

The Modified Chlorophyll Absorption Ratio Index 2 (MCARI2) was developed to improve the estimation of green vegetation properties such as leaf area index (LAI) and canopy chlorophyll content. Vegetation reflects and absorbs light differently depending on leaf pigments and canopy structure. Chlorophyll pigments strongly absorb red light (from 0.6 to 0.7 µm) for photosynthesis, while the cell structure of leaves strongly reflects near-infrared (NIR) light (from 0.7 to 1.1 µm). Green light (around 0.55 µm) is less absorbed by chlorophyll and provides additional sensitivity to vegetation vigor.

A limitation of simpler indices like the Normalized Difference Vegetation Index (NDVI) is that they can saturate at high biomass levels and are influenced by soil background effects. To address these challenges, Haboudane et al. (2004) introduced MCARI2, which combines the sensitivity of chlorophyll absorption in the red band, reflectance in the green band, and scattering in the NIR band. MCARI2 also incorporates a normalization term that reduces the influence of soil background and canopy structure, making it more robust for estimating vegetation properties across a wide range of conditions.

References

Haboudane, D., Miller, J. R., Pattey, E., Zarco-Tejada, P. J., & Strachan, I. B. (2004). Hyperspectral vegetation indices and novel algorithms for predicting green LAI of crop canopies: Modeling and validation in the context of precision agriculture. Remote sensing of environment, 90(3), 337-352.