**1. Introduction**

As one of the highest and largest highlands in the world, the Tibetan Plateau (TP) is referred to as "the Third Pole" [1]. It contains abundant water resources with a large number of lakes, rivers, glaciers, frozen soils, and wetlands [2–4]. The TP is the source of several major rivers in Asia, which provide water for the surrounding areas, and has crucial impacts on the development of the Asian economy and civilization [1,5]. Thermodynamic forcing is closely connected to the water cycle of the TP through the "CISK-like mechanism" [6]. It also plays a critical role in Asian atmospheric circulations and thus the weather and climatic systems, such as the plateau vortices, Asian monsoon rainfall, and even the tropical signal [7–10]. As an important component of the atmospheric heat source in warm seasons, surface sensible heating (SH) can regulate the onset and maintenance of Asian summer monsoon systems confirmed by observations and numerical experiments [11–13]. In the preceding spring, the variability of SH over the TP is well connected to the onset of the East Asian summer monsoon, as well as the precipitation anomalies of East China [14,15]. In addition, the interannual variation of SH can regulate surface dust concentrations over the East Asian dust source region and the northwestern Pacific through increasing the westerly winds [16].

In consideration of the critical role of SH over the TP on surrounding weather and climate systems, research into variations of SH over the TP has important impacts for improving the understanding of the mechanism of the TP and the variability in Asian climate systems. Trend analysis indicated that SH over the TP presented significant weakening during the 1980s–2000s, which is due to the reduced surface wind speed in connection with the East Asian subtropical westerly jet under global warming [17]. Recent studies have indicated that SH over the TP has been dominated by a slightly increasing trend since the late 1990s as a result of the restored surface wind speed and difference in ground-air temperature [18]. The CMIP6 models demonstrated that SH will continue to increase in the future [19]. Moreover, the long-term trend of SH features elevation dependence with a greater variation trend at a higher elevation [20]. Observational analysis and numerical experimentation indicated that the early spring sea surface temperature anomalies over the North Atlantic can significantly impact the interannual variation of spring SH of the TP by triggering eastward propagating wave trains and intensifying the subtropical westerly jet [21,22]. Based on satellite data and observations, a recent study found that SH over the TP has increased slightly since 2001 [23].

Summer SH over the TP plays a key role in the surrounding weather and climate systems. Numerical simulations indicated that summer SH can enhance both the lowerlevel convergence and upper-level divergence in the TP, intensify the rising motion, and thus enhance the South Asia High [24]. Chen et al. [25] found that the disappearances of the TP vortices in the sloping terrain of the eastern TP might be attributed to the weakening of SH. Studies also showed that summer SH has crucial impacts on Sichuan-Chongqing areas [26]. However, although the trends of summer SH as a result of climatic change were investigated by previous research [17–19], few studies have investigated the interannual and interdecadal variations in summer SH of the TP and their possible causes, which is necessary for us to understand the changes in the Asian weather and climate. Therefore, the present study aims to investigate the interannual and interdecadal variations in summer SH over the TP and their associated mechanisms. This helps us to gain a deep understanding of the land and atmosphere interaction over the TP during warm seasons.

### **2. Data and Methods**
