Summary Results from:

Multi-scale evaluation of global gross primary productivity and evapotranspiration products derived from Breathing Earth System Simulator (BESS)
As they relate to the validation of mod16

Authors: Jiang, C. and Ryu, Y.

Source: Remote Sensing of Environment, 186, pp.528-547

Link to: Access Publication

Abstract:

Several global gross primary production (GPP) and evapotranspiration (ET) remote sensing products exist, mainly provided by machine-learning (e.g. MPI-BGC) and semi-empirical (e.g. MODIS) approaches. Process-based approaches have the advantage of representing the atmosphere-vegetation-soil system and associated fluxes as an organic integration, but their sophistication results in a lack of high spatiotemporal resolution continuous products. Targeting this gap, we reported a new set of global 8-day composite 1-km resolution GPP and ET products from 2000 to 2015, using a simplified process-based model, the Breathing Earth System Simulator (BESS). BESS couples atmosphere and canopy radiative transfer, photosynthesis and evapotranspiration, and uses MODIS atmosphere and land data and other satellite data sources as inputs. We evaluated BESS products against FLUXNET observations at site scale (total of 113 sites, 742 site years), and against MPI-BGC products at global scale. At site scale, BESS 8-day products agreed with FLUXNET observations with R2=0.67 and RMSE=2.58gC m_2 d_1 for GPP, and R2=0.62 and RMSE=0.78mm d_1 for ET, respectively, and they captured a majority of seasonal variability, about half of spatial variability, and a minority of interannual variability in FLUXNET observations. At global scale, BESS mean annual sum GPP and ET maps agreed with MPI-BGC products with R2=0.93 and RMSE=229gC m_2 y_1 for GPP, and R2=0.90 and RMSE=118mm y-1 for ET, respectively. Over the period of 20012011, BESS quantified the mean global GPP and ET as 122&plusmin;25PgC y-1 and 65×103&plusmin;11×103km3 y_1, respectively, with a significant ascending GPP trend by 0.27PgC y_2 (p<0.05), similar to MPI-BGC products as well. Overall, BESS GPP and ET estimates were comparable with FLUXNET observations and MPI-BGC products. The process-based BESS can serve as a set of independent GPP and ET products from official MODIS GPP and ET products.