Improved estimation of photochemical reflectance index using MODIS ocean bands

Abstract

The photochemical reflectance index (PRI) derived from narrow bands reflectance at 531 and 570 nm is related to the light use efficiency (LUE) of terrestrial vegetation. However, the satellite sensor that has these two spectral bands has not existed so far. Therefore, it is necessary to substitute PRI using spectral bands of current satellite sensors. In this study, first we investigated the effectiveness of PRI alternatives by the band combination and the multiple regression analyses that used the MODIS land and ocean band reflectance simulated from ground observation data. In the band combination analysis, it was possible to substitute PRI when each growth stage of vegetation was separately analyzed. But, it was difficult to substitute PRI by a single equation in all growth stages of vegetation. In the multiple regression analysis, it was possible to substitute PRI by using the logarithms of MODIS land and ocean band reflectance even when all growth stages of vegetation were analyzed at the same time. Second we verified accuracy of alternative by the multiple regression analysis that used the logarithm of MODIS ocean band reflectance to apply the different observation periods and sites data. It was found that the error was 0.011 in RMSE and this corresponds to 10% error of LUE. Finally we applied this PRI alternative to the actual MODIS. It was possible to show the changes of the PRI alternative by spatial pattern and land surface cover types.