Terra-P: a New Global Monitoring System for Primary Production

The TerrA-P project is developing a new global monitoring system for primary production by land ecosystems, designed for Sentinel-3 green vegetation cover and land surface temperature inputs. At its core is a universal, parameter-sparse, first-principles light use efficiency model (the ‘P’ model) for gross primary production (GPP) by $\mathrm{C}_{3}$ and $\mathrm{C}_{4}$ plants. The P model is derived mathematically from the standard model of photosynthesis, with the addition of optimality hypotheses that skilfully predict the acclimation of photosynthetic capacities and the leaf-internal partial pressure of carbon dioxide (CO2), The system has no need of biome-specific parameter values, and realistically incorporates the influence of rising atmospheric CO2. Multiple seasonal cycles of modelled and observed GPP were compared in a calibration data set of eddy-covariance GPP data at 17 sites. Optimal agreement was obtained after a small adjustment, within the accepted range, of the intrinsic quantum efficiency for $\mathrm{C}_{3}$ photosynthesis.