Global land surface 250 m 8 d fraction of absorbed photosynthetically active radiation (FAPAR) product from 2000 to 2021

Abstract. The fraction of absorbed photosynthetically active radiation (FAPAR) is a critical land surface variable for carbon cycle modeling and ecological monitoring. Several global FAPAR products have been released become widely used; however, spatiotemporal inconsistency remains large issue the current products, their spatial resolutions accuracies can hardly meet user requirements. An effective solution to improve continuity accuracy take better advantage temporal information in satellite data using deep learning approaches. In this study, latest version (V6) product with 250 m resolution was generated from Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance other information, as part Global LAnd Surface Satellite (GLASS) suite. addition, it aggregated multiple coarser (up 0.25∘ monthly). Three existing (MODIS Collection 6; GLASS V5; PRoject On-Board Autonomy–Vegetation, PROBA-V, V1) were used generate time-series training samples, which develop bidirectional long short-term memory (Bi-LSTM) model. Direct validation high-resolution maps Validation Land European Remote sensing Instrument (VALERI) ImagineS networks revealed that V6 has higher than MODIS, V5, an R2 value 0.80 root-mean-square errors (RMSEs) 0.10–0.11 at m, 500 3 km scales, percentage (72 %) retrievals meeting requirement 0.1. evaluation comparison AmeriFlux National Ecological Observatory Network (NEON) sites greater reflects variations vegetation V5 FAPAR. quality attributed ability Bi-LSTM model, involves high-quality samples combines strengths well spectral MODIS information. 8 d 2020 freely available https://doi.org/10.5281/zenodo.6405564 https://doi.org/10.5281/zenodo.6430925 (Ma, 2022a, b) University Maryland 2000–2021 (http://glass.umd.edu/FAPAR/MODIS/250m, last access 1 November 2022).