南昌1736年以来的降雪与冬季气温变化

RECONSTRUCTION OF SNOWFALL AND WINTER TEMPERATURE VARIATIONS IN NANCHANG SINCE 1736

利用清代雨雪分寸记录,重建了南昌1736年以来的初雪日期、降雪日数、降雪量及冬季气温变化序列。分析显示:1)1736～1910年的平均初雪日期比1951～2007年早20天,前一时期约58%的年份初雪日出现于12月,后一时期约51%的年份初雪日出现于1月;2)1736～1910年的冬季平均降雪日数比1951～2007年多4天;1951年以后降雪日数呈逐渐减少趋势,并在1997年发生由多到少的突变;3)1736～1910年的平均降雪量较1951～2007年多28.0mm;1860s和2000s分别为过去300年降雪量最多和最少的年代,二者相差85.6mm;4)1736年以来南昌经历了1790s～1810s和1860s～1900s的寒冷期,1730s～1780s和1820s～1850s的偏冷期,1910s～1980s的偏暖期,以及1990s～2000s的温暖期;其中最寒冷年代(1860s)与最温暖年代(2000s)的冬季气温相差3.0℃。此外,南昌的冬季气温存在34年和45年的变化周期。

The Yu-Xue-Fen-Cun archives,a kind of memos-to-Emperor in the Qing Dynasty, recorded each rainfall and snowfall process and described precipitation conditions at 273 stations covering the whole China. They are considered as one of the most reliable proxies to reconstruct historical climate variations for their high temporal resolution and broad spatial coverage. Based on these historical documents and modern meteorological observations, this paper reconstructed annual snowfall and winter temperature variations from 1736 to 2007 in Nanchang, a city located in the middle-lower reaches of the Yangtze River. The two parameters including date of first snow and winter snow days were directly extracted through these materials, while historical winter snowfall amount and winter temperature were reconstructed by the regression models between modern winter snow days and snowfall amount or winter temperature. Then inter-annual and inter-decadal variability and temporal differences of the climate series were statistically analyzed. The conclusions obtained include that： （1）The first snow of 58% years during 1736 - 1910 occurred in December while that of 51% years during 1951- 2007 occurred in January. The mean beginning date of snowfall during the former period was 20 days earlier than the latter. （2）Winter snow days during 1736 - 1910 were 4 days more than those during 1951 - 2007. The mean snow days of 1790s - 1810s and 1860s - 1870s were 10 -13 days,having the most abundant snowfall in the past 300 years. Winter snow days gradually decreased since 1951 and experienced abrupt change from more to less around 1997. （3）The mean winter snowfall amount during 1736 - 1910 was 28.0ram more than that during 1951 - 2007. The snowfall amount of about 61% years during the former period was more than the mean of the later period. The decadal snowfall difference from the highest value at 1860s to the lowest at 2000s reached to 85.6ram. （4）Winter temperature variation can be divided into four stages, and they were very cold periods during 1790s ~ 1810s and 1860s- 1900s, cold periods during 1730s ~ 1780s and 1820s ~ 1850s,warm period during 1910s ~ 1980s, and very warm period during 1990s- 2000s. The temperature variation amplitude between the coldest decade （1860s）and the warmest（2000s）was 3.0℃,while that between the coldest year （1869） and the warmest （ the years with no snow, such as 2006） was 5.8%, Power spectrum analysis showed that winter temperature in Nanchang in the past 300 years had 34a and 45a cycles. Moreover,our temperature reconstruction agreed well with other cold/warm or temperature time-series in this region.