Coupled Estimation Of daily Gross Primary Production and Evapotranspiration at 84 Global Forest Sites

Gross Primary Production (GPP) and evapotranspiration (ET) play a critical role of the global carbon, water and energy cycle. Accurate quantification of the global GPP and ET could improve our ability to understand global climate change and energy budget. However, most of the GPP and ET remote sensing models fail to take the coupled relationship between vegetation transpiration (Et) and photosynthesis into consideration. More importantly, these models might ignore the difference of transpiration and photosynthesis rate in different groups of leaves (sunlit and shaded). Here, we coupled the estimates of daily GPP and ET at 84 global forest sites based on the Two-Leaf Light Use Efficiency model and the Penman-Monteith equation that were linked by the Ball-Berry conductance model. The developed model was well calibrated with the root mean square error (RMSE) and the coefficient of determination (R2) being 1.97 gC/m2 day and 0.77 for GPP respectively, and being 21.91 W/m
²
and 0.65 for ET, respectively. In the meantime, the validation results demonstrated the good performance of the coupled model, with the RMSE and R2 being 1.95 gC/m2 day and 0.77 for GPP, respectively, and being 21.34 W/m
²
and 0.66 for ET, respectively.