过去千年中国不同区域干湿的多尺度变化特征评估

依据近年发表的新成果,对中国过去千年干湿的年至百年尺度变化特征进行了总结梳理与对比分析,综合评估了20世纪干湿变幅的历史地位。主要结论是：① 根据历史文献记载重建的东中部各区干湿序列在1400年以后均达高信度,但其前因存在记录缺失,仅有半数时段的重建结果达高信度。在东北及内蒙古东部,根据不同地点湖沼沉积物记录揭示的区域干湿百年尺度变化特征在多数时段不一致。在西部的黄土高原、河西走廊、新疆中北部、青藏高原东北部和东南部等地区,利用不同地点树轮资料重建的干湿序列显示的干湿变化特征在区内一致性高。② 过去千年中国各地干湿变化均存在显著的年际、年代际和百年尺度周期。其中准2.5 a、60~80 a和110~120 a等尺度的周期为所有地区共有;3.5~5.0 a、20~35 a等尺度周期则主要发生在东北、东中部地区、黄土高原和青藏高原;而准45 a周期则只发生在东北和东中部地区（均超过90%信度水平）;各区域间的干湿变化位相并不同步。③ 尽管已发现青藏高原东北部20世纪很可能是过去3000 a最湿的世纪之一,但其他大多数区域的重建结果显示：20世纪的干湿变幅在年代际尺度上均未超出其前各个时段的变率范围。

The assessment on hydroclimatic changes of different regions in China at multi-scale during the past millennium

Based on the latest hydroclimatic reconstructions in peer-reviewed scientific journals, we summarize the multi-scale pattern on hydroclimatic changes and assess whether or not the variability of the 20th century is unusual in the context of the past millennium for different regions of China. The main conclusions are as follows: (1) In the central-eastern China, the dry/wet series reconstructed from historical documents after 1400 have high confidence level, while before 1400, the reconstructions only in half of the period have high confidence due to the shortage of records. In northeastern China and eastern Inner Mongolia, centennial-scale reconstructions from lake sediments at multiple sites are in low agreement in most of periods. In Loess Plateau, Hexi Corridor, central to northern Xinjiang, northeastern and southeastern Tibetan Plateau, hydroclimatic reconstructions from tree rings have robust agreement within the same region. (2) All sub-regions of China show significant cycles with 90% confidence level at inter-annual, inter-decadal and centennial scales. The cycles of 2.5 a, 60-80 a and 110-120 a are detected over all the regions, while the cycles of 3.5-5.0 a and 20-35 a mainly occur in the Loess Plateau, Tibetan Plateau, northeastern and central-eastern China. The cycle of quasi-45 a only occurs in northeastern and central-eastern China. Moreover, the hydroclimatic changes are out of phase in different regions. (3) The 20th century is one of the wettest centuries in the past 3000 years in northeastern Tibetan Plateau. However, most series from other regions show that the inter-decadal hydroclimatic variability of the 20th century does not exceed the amplitude of natural variability, which had ever occurred during the past millennium.