Variability and trends in land surface longwave radiation fluxes from six satellite and reanalysis products

Earth surface longwave radiation (SLR), including downward (DLR), upward (ULR), and net (NLR), significantly impacts the budget global climate evolution. However, spatiotemporal variation in SLR remains poorly understood. In this study, three satellite products (GLASS-MODIS V40, GLASS-AVHRR, CERES-SYN) reanalysis datasets (ERA5, MERRA-2, GLDAS) were validated using ground measurements from 288 sites at seven observation networks. The mean biases root square errors of monthly DLR (ULR, NLR) estimates six −6.36 (−3.56, −2.86) Wm-2 16.63 (14.33, 13.38) Wm-2, respectively. Large differences spatial distribution mainly observed high-latitude, high-altitude desert/barren-covered regions. interannual variability was detected high latitudes. GLASS-AVHRR ERA5 better captured long-term ULR, whereas MERRA-2 trends NLR. An increasing trend ULR between 1982 2015, followed by a decreasing 2016 to 2021; NLR flux did not exhibit significant trend. Overall, more accurate stable than those other accuracy, distribution, analysis.