关中平原明代霜雪灾害特征及小波分析研究

Frost and Snow Disaster and Change Periods in Guanzhong Plain in Ming Dynasty

通过对关中平原明代历史文献资料的搜集和统计分析,研究了该区明代霜雪灾害等级、阶段与灾害发生周期等。结果表明,关中平原明代霜雪灾害可划分为轻度、中度、重度三级,各占总灾害频次的23%,54%,23%。该区明代霜雪灾害可划分为4个阶段,第1阶段(1368～1448年)和第3阶段(1508～1568年)为灾害少发期,第2阶段(1449～1507年)和第4阶段(1569～1644年)为灾害多发生期。小波分析显示,关中平原明代轻度、中度和重度霜雪灾害分别存在11 a、8 a、44 a的周期变化。初步确定关中平原明代1618～1631年发生了1次寒冷气候事件。

Based on collecting, reorganizing and analyzing the history data about the Guanzhong Plain during the Ming Dynasty, the grade series, stage changes and different grades＇ periodicity of the frost and snow disaster are studied in this study. The statistical results show that, frost and snow disaster of the Ming Dynasty had 22 times altogether, and occurred averagely one time per 12.6 years. The Guanzhong Plaint frost and snow disaster grade may be divided into mild, moderate and severe disaster in the Ming Dynasty, and their occurrence probabilities are 26%, 52% and 22%. The disaster has been divided into four uneven periods in the Guanzhong Plain. The first period （1368 -1448）, and the third one （1508 -1568） had the fewer disasters in the Guanzhong Plain, and there were the more disasters during the second period （1449 -1507）, and the fourth one （1569 -1644）. The frequency of frost and snow disasters was obvious upward in the Guanzhong Plain. Wavelets analysis has the characteristics of multi - resolution analysis and ability of expressing local features of signal in both time and fre- quency domains, which is a local analysis method. This novel method is suitable for complex natural disaster systematic. The spatial distribution, temporal evolution and multi - scale period of the frost and snow disaster are studied from the year of 1368 to 1644, applying wavelet analysis method and the history data about the Guanzhong Plain during the Ming Dynasty. The result of wavelet analysis shows, the mild, moderate, severe disaster occurrence periodicity is respectively 11, 8 and 44 years. The change of frost and snow disaster in the Guanzhong Plain during the Ming Dynasty is significant. This phenomenon can indicate climate change of the Ming Dynasty. On the basis degree of the frost and snow disaster, mean annual temperature can be reconstruc- ted. There was one cold climatic event in the Guanzhong Plain in Ming Dynasty, occurring between 1618 and 1631, and the temperature was obviously lower than the other time of Ming Dynasty and the modem. There are six disasters in the period, including one - time moderate frost and snow disaster, 5 - times severe frost and snow disasters. The frost and snow disaster occurred averagely one time per 2.3 year during the period. The degree and frequency frost and snow disaster is greater than that of the other time of Ming Dynasty. The result can indi- cate that there is the little ice age of Ming Dynasty. The results mentioned above indicate that the primary cause of the frequency of frost and snow disasters in the Guanzhong Plain was sudden drop of air temperature caused by sustainable snowfall, accumulated snow and cold snap.