Tree-ring based evidence of the multi-decadal climatic oscillation during the past 200 years in north-central China

摘要

As the northern fringe of the Asian summer monsoon region, north-central China (hereafter NCC) is highly sensitive to climate change. It is important to understand drought variability and the associated mechanisms in this region since precipitation changes have direct impacts on human society in this semiarid-arid area. In this study, a new tree ring-width based drought reconstruction (AD 1804-2010) was established in the Songmingyan Nature Reserve, which lies in NCC. This reconstruction illustrates the severe drought periods occurring in the 1860s, 1928-1932 and 1991-2000, with recurring drought intervals being about 60 years. The first principal component of the five chronologies from NCC shows strongly coherent drought variability with the other single-site records and can thus be used as an indicator of regional moisture variations. Combining the Monsoon Asia Drought Atlas (hereafter MADA) dataset and the dry-wet index (hereafter DWI) dataset from eastern China, the spatial distribution of moisture variability for three selected drought events is mapped. It is found that northern China and Mongolia experienced dry conditions during the three severe drought periods, whereas wet conditions prevailed in the middle and lower reaches of the Yangtze River. The Pacific Decadal Oscillation (hereafter PDO) might have been one of the possible causes responsible for multi-decadal drought variability over NCC, with the PDO warm phases being associated with drought conditions and the cold phases corresponding to wet conditions over NCC