Primary production data for the Indian Ocean sector of the Southern Ocean
Description
Validation of primary production models with the in-situ NPP estimated using 13C tracer during the Southern Ocean expedition-2009/2010
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In order to analyze the Aqua-MODIS derived net primary production (NPP) for its utility in the Southern Ocean, we have validated three ocean-color based models such as the vertically generalized production model (VGPM), Eppley-VGPM, and carbon-based productivity model (CbPM) for selecting the best model for the study region. We evaluated the performance of these models by comparing with the in-situ NPP estimated using 13C tracer during the Indian scientific expedition to the Southern Ocean in 2009. The detail method of 13C measurement was documented in the previous work (Gandhi et al., 2012). The VGPM was developed for estimation of NPP from chlorophyll accounting into temperature dependency of chlorophyll-specific photosynthetic efficiency. The Eppley-VGPM makes use of an exponential function developed from changes in growth rates of phytoplankton over varied temperature ranges for a wide variety of species. Further, a new CbPM model was developed that uses the backscattering coefficients and chlorophyll-to-carbon ratios for estimation of phytoplankton carbon biomass and phytoplankton growth rates, respectively. The model based NPP values were available in weekly time scale with a spatial resolution of ~4 km. The pixel values from the models were extracted around each in-situ observation to generate the matchups for the validation strategy, a method adopted by several authors (Jena, 2017).