A GPP assimilation model for the southeastern Tibetan Plateau based on CO2 eddy covariance flux tower and remote sensing data.

The gross primary production (GPP) at individual CO 2 eddy covariance flux tower sites (GPP Tower ) in Dali (DL), Wenjiang (WJ) and Linzhi (LZ) around the southeastern Tibetan Plateau were determined by the net ecosystem exchange of CO 2 (NEE) and ecosystem respiration ( R e ). The satellite remote sensing-VPM model estimates of GPP values (GPP MODIS ) used the satellite-derived 8-day surface reflectance product (MOD09A1), including satellite-derived enhanced vegetation index (EVI) and land surface water index (LSWI). In this paper, we assembled a subset of flux tower data at these three sites to calibrate and test satellite-VPM model estimated GPP MODIS , and introduced the satellite data and site-level environmental factors to develop four new assimilation models. The new assimilation models’ estimates of GPP values were compared with GPP MODIS and GPP Tower , and the final optimum model among the four assimilation models was determined and used to calibrate GPP MODIS . The results showed that GPP MODIS had similar temporal variations to the GPP Tower , but GPP MODlS were commonly higher in absolute magnitude than GPP Tower with relative error (RE) about 58.85%. While, the assimilation models’ estimates of GPP values (GPP MODEL ) were much more closer to GPP Tower with RE approximately 6.98%, indicating that the capacity of the simulation in the new assimilation model was greatly improved, the R 2 and root mean square error (RMSE) of the new assimilation model were 0.57–4.90% higher and 0.74–2.47 g C m −2 s −1 lower than those of the GPP MODIS , respectively. The assimilation model was used to predicted GPP dynamics around the Tibetan Plateau and showed a reliable result compared with other researches. This study demonstrated the potential of the new assimilation model for estimating GPP around the Tibetan Plateau and the performances of site-level biophysical parameters in related to satellite-VPM model GPP. [ABSTRACT FROM AUTHOR]