Consistent Ground Surface Temperature Climatology Over China: 1956-2022

The ground surface represents the land-atmosphere interface and plays a crucial role in exchanging energy, matter, and biochemical fluxes. The ground surface temperature (Ts) is hence widely investigated as an indicator to understand the thermal state of soil in a warming world. However, regular and continuous Ts measurements are rare worldwide, and the early Ts records were derived from snow surface measurements and are not comparable with the measurements of modern automatic systems. In this study, we reconstruct the Ts records of the China Meteorological Administration (CMA) for 1956-2022 by numerical simulation. The results show that the mean annual ground surface temperature (MAGST) during 1981-2010 ranged from 0.4 to 30.8 degrees C at 632 stations. The MAGST was mainly controlled by air temperature and refined by snow depth. The overall MAGST increased by 0.20 +/- 0.02 degrees C dec-1 across China during 1956-2022 and showed pronounced interdecadal variability corresponding to the surface air temperature (0.23 +/- 0.03 degrees C dec-1). At the snow-covered sites, the Ts warming was amplified by increased snow depth, leading to about 0.24 degrees C dec-1 (or 70.6%) faster warming for Ts in winter compared to that of surface air temperature. Many of the early reported ground surface temperature studies based on CMA measurements did not consider the measurement inconsistency and likely overestimated the warming trend of ground surface temperature over China. Ground surface temperature (Ts) affects a variety of temperature-related phenomena on the Earth's surface and is hence widely investigated as an indicator to understand the interaction of land-atmosphere in a warming climate. However, continuous Ts measurements are rare worldwide. Restricted by the early measurement conditions, the early Ts records were recorded manually from the snow surface, and are not comparable with the measurements of the modern automatic systems. Therefore, we reconstructed a Ts time series for the China Meteorological Administration (CMA) data for 1956-2022 by numerical simulation. Our results show that the mean annual ground surface temperature (MAGST) increased by 0.20 degrees C dec-1 across China during 1956-2022. The MAGST was mainly controlled by air temperature and refined by snow depth. Ts warming was amplified by about 0.24 degrees C dec-1 (or 70.6%) in winter by increased snow depth since 1970, compared to the surface air temperature. Many of the early reported Ts studies based on CMA measurements did not consider the measurement inconsistency and likely overestimated the warming trend of Ts over China. Continuous ground surface temperature data for China were estimated by filling the gaps arising from the inconsistent measurement systems The overall mean annual ground surface temperature increased by 0.20 +/- 0.02 degrees C dec-1 across China during 1956-2022 Ground surface temperature warming was amplified by about 0.24 degrees C dec-1 (or 70.6%) in winter since 1970 due to increased snow depth