Satellite sensors have provided a wealth of critical data over the past decades. In particular, the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Terra and Aqua satellites has been important for determining terrestrial gross primary productivity. Both satellites may reach the end of their lifetime this year, meaning that MODIS data coverage will also end. Newer satellites using a different sensor, the Visible Infrared Imaging Radiometer Suite (VIIRS), could be used to continue the record, important for determining climate change impacts on and feedbacks to the terrestrial carbon cycle. However, the two sensors need to be benchmarked to each other in order to provide such a continuous dataset once MODIS is no longer in use.
K. Arthur Endsley from the University of Montana, Maosheng Zhao, an SSAI scientist at NASA, and colleagues do just this using a combination of models and observational data. They used carbon dioxide fluxes from eddy covariance towers along with field measurements of productivity and biomass and a global dataset of plant traits to calibrate the models using MODIS data for use with VIIRS data. They determined terrestrial productivity from models using both MODIS and VIIRS data to be 127 PgC per year from 2012 to 2018, aligning well with other estimates. Productivity shows increasing trends from 2000 to 2018, but with a decrease in the growth rate from 2012 to 2021. These results are important as they allow the extension of satellite estimates of terrestrial primary productivity — a central climate–carbon feedback — to 2030.
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