Diurnal variation of NDVI from an unprecedented high-resolution geostationary ocean colour satellite

Abstract

The Geostationary Ocean Color Imager (GOCI) is the first ocean-colour geostationary satellite sensor which provides hourly 500-m, multi-spectral band data. We present the first exhibit of the spatio-temporal variations of Normalized Difference Vegetation Index (NDVI) values from unprecedented GOCI data. Comparisons of NDVIs from GOCI and in-situ reflectances, with GOCI spectral response functions applied, indicate fairly good correlations (r approximate to 0.991). 500-m GOCI NDVI data revealed clear, bell-shaped diurnal variations with a maximum at 12:30 PM followed by a rapid decline in the afternoon. This study also presented the first exhibit of diurnal responses by different forest species, in this case deciduous broadleaf, evergreen and grassland types of species, with high correlations between the observed and estimated NDVIs. All of the plant species demonstrated a similar type of diurnal variation with a characteristic bell-shaped pattern. These findings can enhance our understanding of the relationship between land ecology and carbon dioxide flux.