关键词: 关中平原, 明代, 霜雪灾害, 小波分析, 寒冷气候事件

Abstract:

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 Plain's 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 frequency 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 reconstructed. 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 modern. 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 indicate 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.

Key words: Guanzhong Plain, Ming Dynasty, frost and snow disaster, wavelet analysis, cold climatic event