A long-term 1 km monthly near-surface air temperature dataset over theTibetan glaciers by fusion of station and satellite observations

Surface air temperature (SAT) is a key indicator of global warming and plays an important role in glacier melting. On the Tibetan Plateau (TP), there exists a large number of glaciers. However, station SAT observations on these glaciers are extremely scarce, and moreover the available ones are characterized by short time series, which substantively hinder our deep understanding of glacier dynamics due to climate changes on the TP. In this study, an ensemble learning model is constructed and trained to estimate glacial SATs with a spatial resolution of 1 km x 1 km from 2002 to 2020 using monthly MODIS land surface temperature products and many auxiliary variables, such as vegetation index, satellite overpass time, and near-surface air pressure. The satellite-estimated glacial SATs are validated against SAT observations at glacier validation stations. Then, long-term (1961-2020) glacial SATs on the TP are reconstructed by temporally extending the satellite SAT estimates through a Bayesian linear regression. The long-term glacial SAT estimates are validated with root mean squared error, mean bias error, and determination coefficient being 1.61 degrees C, 0.21 degrees C, and 0.93, respectively. The comparisons are conducted with other satellite SAT estimates and ERA5-Land reanalysis data over the validation glaciers, showing that the accuracy of our satellite glacial SATs and their temporal extensions are both higher. The preliminary analysis illustrates that the glaciers on the TP as a whole have been undergoing fast warming, but the warming exhibits a great spatial heterogeneity. Our dataset can contribute to the monitoring of glaciers' warming, analysis of their evolution, etc. on the TP. The dataset is freely available from the National Tibetan Plateau Data Center at https://doi.org/10.11888/Atmos.tpdc.272550 (Qin, 2022).