Driven by human activities and global climate change

the climate on the Qinghai-Xizang Plateau is experiencing a warming and humidifying trend. It significantly impacts the thermal-moisture dynamics in the active layer of the permafrost

which in turn affects the ecological environment of cold regions and the stability of cold region engineering. While the effect of air temperature on permafrost thaw has been well quantified

the processes and mechanisms behind the thermal-moisture response of the permafrost under the combined influence of increased rainfall and rising air temperature remain contentious and largely unknown. A coupled model was applied to quantify the impacts of increased rainfall

rising air temperature

and their compound effects on the thermal-moisture dynamics in the active layer

considering the sensible heat of rainwater in the ground surface energy balance and water balance process. The results indicate that the compound effect of warming and humidifying resulted in a significant increase in surface net radiation and evaporation latent heat

a more significant decrease in surface sensible heat

and a smaller impact of rainfall sensible heat

leading to an increase in surface soil heat flux. The compound effect of warming and humidifying leads to a significant increase in the liquid water flux with temperature gradient. The increase in liquid water flux due to the temperature gradient is larger than that of warming alone but smaller than the effect of humidifying alone. Warming and humidifying result in a smaller increase in soil moisture content during the warm season compared to rainfall increases alone. The thermal conductivity heat flux in the active layer increases significantly during the cold season but less than the effect of warming alone. The convective heat flux of liquid water flux increases noticeably during the warm season but less than the effect of rainfall increases alone. Increased rainfall significantly cools the soil during the warm season

while both warming and humidifying lead to a more pronounced warming effect on the soil during the cold season than during the warm season. An increase in the average annual temperature by 1.0℃ leads to a downward shift of the permafrost table by 10 cm

while an increase in rainfall by 100 mm causes an upward shift of the permafrost table by 8 cm. The combined effect of warming and humidifying results in a downward shift of the permafrost table by 6 cm. Under the influence of climate warming and humidifying

the cooling effect of increased rainfall on permafrost is relatively small

and the warming effect of increased temperature still dominates.