Impact of Pacific Walker Circulation driven by Interdecadal Pacific Oscillation on precipitation variability in the North China Monsoon Marginal Region over the past five centuries

The Asian Summer Monsoon system has exerted significant impact on the ecological environment and socio-economic development of North China. Understanding the variability of monsoon precipitation and its underlying drivers in the context of anthropogenic warming necessitates the development of high-resolution precipitation reconstructions extending beyond the instrumental record. This study presents a novel tree ring network comprising 869 cores from 12 site chronologies in the North China Monsoon Marginal Region (NCMMR). A Nested Principal Component Regression model is used to reconstruct August-to-July precipitation variability from 1512 to 2021. The results indicate that, compared to the preceding five centuries, the probability of extreme high and low precipitation events increased by ~9 % and ~ 2 %, respectively, during the Current Warming Period (CWP, 1850–2021), with a higher long-term mean precipitation of 465.39 mm. The standard deviation and coefficient of variation for precipitation during the CWP (48.24 mm and 10.36 %, respectively) exceed those of the Historical Period (1512–1849) (36.89 mm and 8.07 %, respectively), highlighting an increase in precipitation variability over time. Analysis of global sea surface temperature patterns reveals a strong linkage between precipitation and the Interdecadal Pacific Oscillation (IPO). This is supported by a significant negative correlation between precipitation and the IPO index (P < 0.001), alongside the IPO's substantial contribution (25 % of explained variance) to precipitation variability. Additionally, precipitation exhibits a significant positive correlation with the Pacific Walker Circulation (PWC) index (P < 0.001). Climate model simulations further demonstrate that IPO-driven variations in PWC intensity regulate interdecadal precipitation variability in the NCMMR using water vapor transport anomalies.

亚洲夏季风系统对华北地区的生态环境与社会经济发展具有显著影响。在人为变暖的背景下，理解季风降水的变率及其驱动机制，需要构建超越器测记录的高分辨率降水重建序列。本研究建立了一套全新的树轮网络，涵盖华北季风边缘区（North China Monsoon Marginal Region，NCMMR）12个样点年表的869个树芯样本。研究采用嵌套主成分回归（Nested Principal Component Regression）模型，重建了1512年至2021年8月至次年7月的降水变率。结果显示，相较于此前五个世纪，现代暖期（Current Warming Period，CWP，1850–2021）内极端偏多与极端偏少降水事件的发生概率分别提升了约9%与约2%，且该时段长期平均降水量达465.39 mm，处于更高水平。现代暖期内降水的标准差与变异系数分别为48.24 mm与10.36%，均高于历史期（1512–1849年）的36.89 mm与8.07%，反映出降水变率随时间呈增强趋势。对全球海表温度模态的分析揭示，降水变化与太平洋年代际振荡（Interdecadal Pacific Oscillation，IPO）存在紧密关联。这一结论得到了降水与IPO指数显著负相关（P < 0.001）的佐证，同时IPO对降水变率的解释方差贡献达25%。此外，降水与太平洋沃克环流（Pacific Walker Circulation，PWC）指数呈显著正相关（P < 0.001）。气候模式模拟进一步证实，IPO驱动的太平洋沃克环流强度变化通过水汽输送异常调控华北季风边缘区的年代际降水变率。