The effect of precipitation-induced advective heat on permafrost in the Tibetan Plateau

The Tibetan Plateau (TP), China, contains the world’s largest permafrost area outside the Polar Regions. This study investigates the precipitation-induced advective heat flux ( E Pre ), which represents the energy transfer resulting from the temperature difference between rainfall and soil. Observational data from three permafrost monitoring sites (Qumalai, Xidatan, and Tanggula) were combined with simulations from the Community Land Model version 5.0 (CLM5.0) to quantify E Pre precipitation infiltration depth, and the probability of infiltration reaching the frozen soil layer. The analysis further examines how precipitation amount, soil texture, soil moisture, and freeze–thaw state jointly control infiltration processes and influence the soil thermal regime. Infiltration depth varies with initial soil moisture and precipitation duration, from shallow retention to deep percolation. E Pre is generally negative, with maximum cooling of −84.14 W m⁻² at QML, −73.24 W m⁻² at XDT, and −56.63 W m⁻² at TGL, but becomes positive during prolonged summer rainfall, reaching 45.43 W m⁻² at QML. Diurnal soil temperature variations shift E Pre from cooling by day to reduced cooling or warming at night. Across the TP, mean infiltration depth is ∼5 cm, higher in southeastern Tibet, with a regional mean E Pre of −0.08 W m⁻². Warming effects are concentrated in the southeastern and central TP, while cooling dominates the arid west and high-elevation north. • Precipitation-induced advective heat is quantified and incorporated into CLM5.0. • Continuous rainfall changes advective heat from cooling to warming on permafrost. • Normal rainfall can warm soil when infiltration reaches permafrost.