The Development of Global GPP and ET Products of Enhanced BESS Model Derived from GCOM-C SGLI Datasets

Remote sensing-based global carbon flux and water products have gained worldwide prominence due to their feasibility to capture spatial patterns, interannual variability and long-term trend of ecosystem carbon and water dynamics from landscape to global scales. The Breathing Earth System Simulator (BESS), a sophisticated coupled process-based diagnostic terrestrial model, integrates multiple physical and bio-geological processes, including atmospheric transfer, canopy radiative transfer, and soil system. BESS has demonstrated robust performance across temporal and spatial scales from 1982 to 2019 when equipped with MODIS Atmosphere and Land products. This study aims to produce global gross primary productivity (GPP) and evapotranspiration (ET) products from 2018 to 2024 using the BESS model, utilizing datasets such as land surface temperature (LST), albedo, leaf area index (LAI), and shortwave radiation (SWR) from the GCOM-C SGLI satellite. Operated by JAXA, Japan, GCOM-C SGLI provides medium spatial resolution (250 m to 1 km) and an 8-day temporal resolution, offering improved sensor stability compared to BESS’s default inputs from MODIS datasets. The main results of this study are: (1) The initial GPP and ET outputs showed fine showed fine linear relations with measurements of GPP (R² = 0.56), and ET (R² = 0.45) from 300 collected global flux sites from Fluxnet Ameriflux, Ozflux, Asiaflux; (2) Interannual variations from in response to climate extremes were captured, such as the 2020 Russian heatwave and the 2022 extreme dry summer in southwestern China. (3) From a sensitivity analysis of 21 BESS input parameters, 8 were selected and optimized using the Distributed Alternating Direction Method of Multipliers (D-ADMM), resulting in improved performance with GPP (R² = 0.81) and ET (R² = 0.72). Our GPP and ET products (250m and 1km) will be soon released on the JAXA website, aiming to improve better understanding of global climate and carbon cycle changes.