全新世中国北方季风降水“滞后”日射变化的模拟研究

在亚轨道-轨道尺度上，北半球夏季日射是东亚夏季风（EASM）变化的主要驱动力。然而重建资料揭示，在全新世，反映EASM变化的中国北方季风降水峰值出现在全新世中期左右，明显滞后北半球夏季日射峰值3~4ka。研究该“滞后”问题有利于全面认识古东亚季风的驱动机制，具有重要科学价值。以往研究多关注全新世早期北半球冰盖的作用。现代观测表明中国季风雨带存在季节内的南北推进，中国北方季风降水集中在后夏。因此，在全新世，中国北方季风降水可能主要受北半球后夏日射驱动，而非夏季平均日射，这可能是造成上述“滞后”问题的重要原因之一，但目前研究较少涉及。此外，冰盖与日射对全新世中国北方季风降水变化的相对贡献如何也尚不清楚。因此，本项目将利用数值模式并结合地质记录，研究全新世中国北方季风降水的主导日射及其响应机制，探讨北半球冰盖对中国北方降水的影响及机理。两者相结合，为深入理解全新世东亚季风的驱动机制提供参考。

The boreal summer solar insolation is the main driver of the East Asian summer monsoon (EASM) at orbital-suborbital scale. During the Holocene, multi-resource proxies indicated that the EASM precipitation over North China peaked at middle Holocene (~6 ka BP), which apparently lagged the boreal summer insolation by 3-4 kyr. Understanding of such “lead-lag” phase relationship could deepen our knowledge of the EASM variation and possible drivers during the Holocene. Previous studies focused on the role of high-latitude ice sheets over North Hemisphere during the early Holocene. It should be noted that, based on modern observations, the North China monsoonal precipitation concentrates in July-August. Therefore, we suggest that the North China monsoonal precipitation may be regulated by the variation of late summer insolation rather than the summer mean insolation during the Holocene, thus exhibiting the seeming“lag” between the monsoonal precipitation over North China and summer insolation. This mechanism, however, has been seldom mentioned in literature until now. Furthermore, the relative roles of ice sheets and insolation on precipitation remain unclear. Therefore, we plan to use climate models to investigate the variation of the EASM precipitation over North China and its dominant insolation as well as the role of ice sheets, which may help to explain the “lead-lag” monsoonal precipitation-insolation relationship.