The Qinghai-Tibet Plateau (QTP) has prominent seasonal variations in rainfall, which affect the thermal-moisture regime of the active layer in permafrost regions. However, few studies have been conducted on the influence of seasonal rainfall on the hydrothermal changes of the permafrost active layer. Therefore, a validated water-vapour-heat (WVH) coupling model that optimises the surface energy boundary conditions was used to investigate the mechanism by which seasonal rainfall affects the hydrothermal state of the permafrost active layer. The findings demonstrated that, under the influence of summer and autumn rainfall, the overall trends of the surface heat flux (G), net radiation ($R_n$), and sensible heat flux ($H_s$) decreased, while the latent heat flux ($L_{w}E$) increased. However, G continued to rise after the spring light rainfall events, indicating that spring rainfall did not alleviate the heat absorption of the soil surface from the atmosphere. The heavy and moderate rainfall events in summer as well as the consecutive rainfall events in autumn significantly increased the shallow soil water content (θ). After the heavy and moderate rainfall events in summer, θ at 5 cm increased by 2.2–4.2%, and the consecutive rainfall events in autumn resulted in a 1.6% increase in θ at the same depth. In contrast, spring rainfall had little impact on θ, as it mainly comprised light rainfall events. Seasonal rainfall ultimately induced soil temperature (T) changes by affecting the water field. Summer rainfall effectively mitigated permafrost warming, followed by autumn rainfall, whereas spring rainfall had little effect on mitigating permafrost warming. Notably, the maximum decrease in T at 5 cm is 5.6 °C after the summer rainfall events.

青藏高原降雨季节变化显着，影响多年冻土区活动层的热湿状况。然而，关于季节性降雨对多年冻土活动层水热变化影响的研究很少。因此，采用经过验证的水-汽-热（WVH）耦合模型来优化地表能量边界条件，研究季节性降雨影响多年冻土活动层水热状态的机制。研究结果表明，在夏秋季降雨的影响下，地表热通量（G）、净辐射（${右}_n$）和显热通量（$H_s$) 下降，而潜热通量 ($L_w乙$） 增加。然而，春季小雨事件后G继续上升，表明春季降雨并没有缓解土壤表面从大气中吸收的热量。夏季强中雨和秋季连续降雨显着增加了浅层土壤含水量（θ）。夏季强降雨和中雨事件后， 5 cm处的θ增加了2.2%~4.2%，秋季连续降雨事件导致同一深度的θ增加了1.6%。相比之下，春季降雨对θ影响较小，主要为小雨事件。季节性降雨最终通过影响水场引起土壤温度（ T ）变化。夏季降雨有效缓解多年冻土变暖，其次是秋季降雨，而春季降雨对缓解多年冻土变暖作用不大。值得注意的是，夏季降雨事件后，5 cm 处的T最大下降量为 5.6 °C。