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通过对陕南清代历史文献资料的搜集、整理和分析,研究了清代(1644-1911年)陕南霜雪灾害等级、阶段变化及不同等级灾害周期性等。统计分析显示,陕南清代发生霜雪灾害28次,平均每9.57年发生一次;霜雪灾害可划分为轻度、中度、重度三级,各占灾害总频次的21%,72%和7%;清代霜雪灾害可分为4个阶段,其中1644-1668年和1819-1868年的第1、第3阶段为灾害多发期,而1669-1818年和1869-1911年的第2、第4阶段为灾害少发期。霜雪灾害的自相似性揭示了灾害的分形性,分形结果显示陕南地区清代各等级灾害呈周期变化,且这些灾害的集中性非常强。陕南清代轻度、中度和重度霜雪灾害发生分别存在着16～18 a,7～8 a和46 a振荡周期。该地区霜雪灾害的发生主要是偏暖月的持续性降雪、积雪或由寒流引起的气温骤降造成的。初步确定陕南清代发生了两次霜雪灾害气候事件,时间在公元1649-1663年和1817-1842年。
Through the collection, collation and analysis of the historical documents and materials in the Qing Dynasty in Southern Shaanxi, the level and stages of frost and snow disasters in southern Shaanxi during the Qing Dynasty (1644-1911) and the cyclical nature of different levels of disasters have been studied. Statistical analysis shows that frost disaster occurred in Qingnan in the southern Shaanxi province 28 times, with an average of 9.57 years. Frost and snow disasters can be divided into mild, moderate and severe levels, accounting for 21% and 72% of the total frequency respectively 7%. The snow frost disaster in Qing Dynasty can be divided into four stages, of which the first and third phases of 1644-1688 and 1819-1868 are the period of multiple disasters, while the second period of 1669-1818 and 1869-1911 The fourth phase is the period of disaster less frequent. The self-similarities of frost-snow disasters reveal the fractal of the disasters. The fractal results show that the disasters of different grades in the Qing Dynasty in Southern Shaanxi have periodic changes, and the concentration of these disasters is very strong. There were 16 ~ 18 a, 7 ~ 8 a and 46 a periods of oscillation in mild, moderate and severe frost and snow disaster in the Southern Shaanxi Province. Frost and snow disasters in the region are mainly caused by the persistent snowfall in the warm month, snow cover or sudden drop in temperature caused by the cold current. It has been preliminarily confirmed that there have been two frost and snowstorm climatic events in the Qing Dynasty in Southern Shaanxi Province, between 1649-1663 AD and 1817-1842 AD.