Generation of angular-normalized, cloud-filled, 0.01°-downscaled land surface temperature from 2018 to 2023 based on official FY-4A dataset

Abstract. Land surface temperature (LST) is an essential climate variable in geophysical, ecological, and environmental research. Remote sensing provides a unique observation approach for obtaining large-scale LST products. However, current official LST datasets (such as FY-4A) are limited by the unaddressed thermal radiation directionality effect and suffer from the spatial discontinuities due to the pervasive presence of clouds. Moreover, geostationary LST products have relatively coarser resolution than those of polar-orbiting satellites due to trade-off between spatial and temporal resolutions. Based on the official hourly FY-4A LST dataset, this study proposes a novel framework for generating angular-normalized, cloud-filled, and 0.01°-downscaled LST (ANCFDS-LST) product, encompassing directional (Tdir), nadir (Tnadir), and hemispherical (Themi) LST layers. First, the angular-normalized Tnadir and Themi were generated using a time-evolving kernel driven model (TEKDM) with the inputs of multi-temporal FY-4A Tdir. Subsequently, hypothetical clear-sky LST was predicted using a CatBoost model optimized via Bayesian methods. The cloudy-sky LST values were then derived through a cloud radiation force (CRF) correction. Finally, the 0.05° all-weather Tdir, Tnadir, and Themi values were downscaled to 0.01° resolution using an improved hybrid downscaling algorithm (IHDA) combining kernel- and fusion-based methods. Taking the daytime clear-sky near-nadir VNP21A1 LST as reference, the 0.05° Tdir before angular-normalization has a root mean squared difference (RMSD) of 4.53 K and a mean bias difference (MBD) of −1.85 K, whereas the angularly normalized Tnadir has a much smaller RMSD of 2.56 K and a better MBD of 0.06 K. For the all-weather Themi, temperature-based validation over 8 sites in the Heihe River Basin and Australia shows a root mean squared error (RMSE) and mean bias error (MBE) of 2.48 and −0.83 K under clear-sky conditions, 3.65 and −1.43 K under cloudy-sky conditions. After the spatial downscaling, the 0.01° all-weather Themi exhibits abundant texture details. The generated LST products over the FY-4A disk from 2018 to 2023 exhibit enhanced angular consistency, spatial continuity, and finer resolution, offering valuable support for subsequent LST-related applications. The ANCFDS-LST data is freely available at https://doi.org/10.11888/RemoteSen.tpdc.303249 (Na et al., 2026).