《翁同龢日记》记录的19世纪后半叶北京的沙尘天气?

依据清代《翁同龢日记》中天气状况的描述，整理出公元1860～1898年间逐月的沙尘天气日数，基于记录完整月份的沙尘天气日数，统计分析了公元1860～1898年北京沙尘天气日数的平均状况和变化特征。分析发现公元1860～1898年，北京年均沙尘天气记录为10.4天，即使不考虑与现代观测记录标准的差别，亦肯定高于1990年代7.7天/年的平均频次；春季是沙尘天气的高发季节，其占全年沙尘日数的百分比达到70%，其中4月和5月两个月的接近53%；其次为冬季，占20%。与公元1961～2000年相比，公元1860～1898年的春季沙尘天气日数百分比偏高10.9%，沙尘天气在春季的集中程度明显偏高。公元1860～1898年间，年沙尘日数和春季沙尘日数均呈波动减少之势；研究时段内，共出现23次2天以上连续（或持续）的沙尘天气过程，最长的一次持续了4天。这些发现将有益于研究气候变化对沙尘天气影响和分析北京沙尘天气的演变规律。

Sand dust weather of Beijing in the later half of 19th century recorded in the book Weng Tonghe Diary

This paper compiled an ancient book named Weng Tonghe Diary written in the late Qing Dynasty by Weng Tonghe and edited by Chen Yijie . First of all, each sand dust record was extracted from this diary. Based on the records of full months, the general status and evolvement character of sand dust weather in Beijing during 1860-1898 A D were analyzed statistically. The following findings were obtained that: 1) The annual average sand dust days of Beijing during 1860 - 1898 A D are 10.4 days which are more than the average frequency (7.7 days/year) of 1990s even ignoring the difference in the standards on sand dust. 2) Sand dust weather mainly appeared in spring when 70% of the sand dust days were recorded with over 50% happening in April and May. Winter was the second high frequent season of sand dust weather appearing, of which the days take up 20 % . 3) Compared with 1961 -2000 A D, sand dust process during 1860 -1898 A D was more highly concentrated in spring. 4) The trend of annual total number of sand dust days decreased from 1860 to 1898 A D, so did the number of sand dust days in spring. 5) During 1860-1898 A D, there were 23 times of sand dust weather process which lasted more than two days, of which the longest one lasted 4 days. These findings may be helpful to studying the impact of climate change on sand dust weather and to analyzing the evolvement regulation of sand dust weather in Beijing.