Evaluation of Spatial and Temporal Variations in the Difference between Soil and Air Temperatures on the Qinghai-Tibetan Plateau Using Reanalysis Data Products

Many extreme meteorological events are closely related to the strength of land-atmosphere interactions. In this study, the heat exchange regime between the shallow soil layer and the atmosphere over the Qinghai-Tibetan Plateau (QTP) was investigated using a reanalysis dataset. The analysis was conducted using a simple metric Delta T, defined as the difference between the temperatures of the shallow soil and the air. First, the performance of 4 widely used reanalysis data products (GLDAS-Noah, NCEP-R2, ERA5 and ERA5-land) in estimating Delta T on the QTP at soil depths of 0 similar to 7 or 0 similar to 10 cm was evaluated during the baseline period (1981-2010); the ERA5-land product was selected for subsequent analysis, because it yielded a better performance in estimating the annual and seasonal ?T and finer spatial resolution than the other datasets. Using the soil temperature at depths of 0 similar to 7 cm and the air temperature at 2 m above the ground, as provided by the ERA5-Land reanalysis dataset, the entire QTP was found to be dominated by a positive Delta T both annually and seasonally during the baseline period, with large differences in the spatial distribution of the seasonal values of Delta T. From 1950 to 2021, the QTP experienced a significant decreasing trend in the annual Delta T at a rate of -0.07 degrees C/decade, and obvious decreases have also been detected at the seasonal level (except in spring). In the southern and northeastern parts of the QTP, rapid rates of decrease in the annual Delta T were detected, and the areas with significantly decreasing trends in Delta T were found to increase in size gradually from summer, through autumn, to winter. This study provides a holistic view of the spatiotemporal variations in Delta T on the QTP, and the findings can improve our understanding of the land-atmosphere thermal interactions in this region and provide important information pertaining to regional ecological diversity, hydrology, agricultural activity and infrastructural stability.

Automated summary

This study investigates the heat exchange between the shallow soil layer and the atmosphere over the Qinghai-Tibetan Plateau using a reanalysis dataset. It evaluates the performance of four widely used reanalysis data products in estimating Delta T and selects the ERA5-Land product for further analysis. The study reveals the spatial and temporal variations of Delta T on the plateau and provides important information for understanding land-atmosphere thermal interactions and their impacts on regional ecological diversity, hydrology, agriculture, and infrastructure stability.