Estimation of the global net primary productivity using NOAA images and meteorological data: changes between 1988 and 1993

A model for net primary productivity (NPP) estimation was developed based on a relationship between NPP estimated by the Chikugo model and the intensity-sum of the normalized difference vegetation index (NDVI) multiplied by the solar radiation during growth periods. There was a clear linear relationship between the estimated NPP and the intensity-sum (R-2 = 0.845), whose slope indicated the average light use efficiency (LUE) of global plants. The NPP estimation model (NDVI-based model), which included growth multipliers of optimum air temperature and soil water stress on vegetation growth with LUE, was developed. NDVI anomalies caused by scattering of volcanic ash from Mt Pinatubo were reduced by a correction based on intensity matching of channels 1 and 2 individually. NDVI retrieved a seasonal change pattern in 1991 and 1992 after the correction. Global NPP between 1988 and 1993 was estimated using the NDVI-based model, corrected NDVI, air temperature and soil water content data. There was a linear relationship between the estimated NPP and NPP observed in forests in China. The average global NPP during the 6 years was about 123 Pg dry weight per year, and the maximum and minimum NPP appeared in 1991 and 1988, respectively.