唐代陕西黄土高原中南部地区洪涝灾害与气候特征

鉴于洪涝灾害对陕西黄土高原中南部地区的生态建设与经济发展影响重大,基于洪灾历史文献记录,结合数理统计、距平分析、连续小波变换及湿润指数等方法,对唐代(公元618—907年)陕西黄土高原中南部地区洪灾发生规律与气候变化进行了分析。结果表明:洪灾发生频次可分为4个阶段:618—637年与728—847年为洪灾高频期; 638—727年与848—907年为洪灾低频期; 受夏季风影响,洪灾发生频次整体变化趋势呈波动下降趋势; 洪灾等级具有2～5 a,5～9 a,20～30 a及52～80 a的周期,推测洪灾的发生与ENSO及PDO正负相位存在一定联系; 空间上,崂山以南的黄土高原沟壑区为洪灾多发区; 气候干湿特征表现为618—637年气候偏湿,638—837年整体偏干但存在10 a及20 a尺度气候偏湿的时期,838—907年以约10 a尺度进入干湿交替状态。唐代陕西黄土高原中南部地区较大洪灾年份与降水持续时间较长、暴雨这类极端降水事件及气候波动频繁存在联系。

Flood Disasters and Climate Characteristics in Tang Dynasty in the Middle South of Loess Plateau in Shaanxi

In view of the significant impact of flood disasters on the ecological construction and economic development of the middle south Loess Plateau in Shaanxi, based on historical records of flood disaster combined with the methods of mathematical statistics, anomaly analysis, continuous wavelet transform, the humidity index method, the varying regularity of flood disasters and the climate change in the middle south of Loess Plateau were analysed in Shaanxi Province in Tang dynasty(618—907 AD). The conclusions are as follows: The frequency of flood disasters can be divided into four stages, 618—637 and 728—847 are the high frequency period of flood disasters, 638—727 and 848—907 are the low frequency period. The variation of flood frequency is affected by the summer monsoon showing a downward fluctuating trend. Flood disaster grade has periods of 2～5 years, 5～9 years, 20～30 years and 52～80 years, inferring flood disaster is related to ENSO and the positive and negative phases of PDO. In terms of space, the high frequency area of flood disaster is mainly located in the gully region of south of Laoshan Mountain. Dry and wet characteristics of Climate were that, the climate was wet during 618—637, dry in 638—837 but existing scales of 10 years and 20 years of wet stage. From 838 to 907, it entered into the state of dry and wet alternation in a scale of about 10 years. In the Tang Dynasty, the major flood years were closely related to the long duration of precipitation, extreme precipitation events such as rainstorm and frequent climate fluctuations.