Enhanced understanding of warming and humidifying on ground heat flux in the Tibetan Plateau Hinterland.

The land surface layer is an important interface between the ground and atmosphere, and cross-surface ground heat flux (G 0) has a significant impact on land surface energy processes and associated cycles. Therefore, understanding dynamics in G 0 is critical for predicting climate changes and developing adaptation strategies. However, the harsh environment and geographic barriers of the Tibetan Plateau have led to a significant lack of observations and soil samples, ultimately limiting the accuracy and application of G 0 calculations. Here we investigated the changes in G 0 at the BJ station, a typical seasonally frozen ground region of the Tibetan Plateau, through soil sampling and long-term in-situ observations. We used the calorimetric method to minimize reliance on model assumptions, aiming to achieve consistent and broadly applicable results. During the freezing-to-thawing and thawing-to-freezing stages, daytime G 0 decreased while nighttime G 0 increased. Conversely, daytime G 0 increased while nighttime G 0 decreased in the completely thawed and completely frozen stages. In moist conditions, more energy was directed toward soil moisture evaporation and vegetation transpiration, whereas in dry conditions, net radiation primarily increased soil temperature, enhancing G 0. Our results revealed the dynamic changes in G 0 across different environmental conditions and their impact on land-atmosphere interactions, and that climate warming and humidifying will diminish the regulatory capacity of G 0. This study highlights the essential requirement for accurate G 0 to predict future climate changes accurately, emphasizing its importance for researchers focusing on land-atmosphere feedback mechanisms and climate modeling. • The minimum and mean G 0 have been increasing while the maximum G 0 decreasing. • More energy is directed toward latent heat flux under moist and warm conditions. • Net radiation primarily increases soil temperature under dry and warm conditions. • The reduction in daytime G 0 leads to insufficient heat release at night. [ABSTRACT FROM AUTHOR]