Changes in summer precipitation over the Tibetan Plateau (TP) significantly influence the surface runoff, river discharge and water availability for the downstream Asian countries, which is sensitive to external forcing. But its response to volcanic eruptions remains unknown. Here we investigate the summer precipitation changes after tropical volcanic eruptions over the TP region by using multiple lines of evidence including reconstructions over the last hundreds of years, observations during recent decades and model simulations covering the last millennium. Both the instrumental data and reconstructions reveal a significant reduction in summer precipitation over the southern TP region during the first summer following tropical volcanic eruptions, which are further confirmed by the coupled model simulations driven by volcanic forcing. The model results indicate that both the dynamic processes related to atmospheric circulation changes and the thermodynamic processes related to specific humidity changes contribute to the decreased precipitation in the southwestern TP, while the thermodynamic process dominates the reduction of precipitation in the southeastern TP. The thermodynamic process results from decreased atmospheric precipitable water caused by decreased surface temperature after tropical volcanic eruptions. The dynamic processes are caused by increased gross moist stability, spatial distribution of surface cooling and a southward shift of westerlies related to weakening and shrinking of Hadley circulation following tropical eruptions. Our results imply that major tropical eruptions have significant impact on the summer precipitation over the southern TP regions, which will further decrease the source of supply for the TP glaciers and runoff output.

青藏高原（TP）夏季降水的变化显着影响下游亚洲国家的地表径流、河流流量和可用水量，这些国家对外强迫敏感。但它对火山爆发的反应仍然未知。在这里，我们通过使用多条证据，包括过去数百年的重建、近几十年的观测和涵盖上个千年的模型模拟，调查了热带火山喷发后青藏高原地区夏季降水的变化。仪器数据和重建均显示，在热带火山喷发后的第一个夏季，高原南部地区夏季降水显着减少，火山驱动的耦合模型模拟进一步证实了这一点。模式结果表明，与大气环流变化相关的动力过程和与比湿变化相关的热力过程均对高原西南部降水的减少有贡献，而热力过程主导了高原东南部降水的减少。热力过程是由于热带火山喷发后地表温度下降导致大气可降水量减少所致。动力过程是由总湿度稳定性增加、表面冷却的空间分布以及与热带喷发后哈德莱环流减弱和收缩相关的西风向南移动引起的。我们的结果表明，主要的热带火山喷发对南部高原地区的夏季降水有显着影响，