Temporal distribution and characteristics of the sand-dust weathers in North China Plain from 1463 to 1913
1463～1913年华北地区沙尘天气序列复原及初步分析

According to more than 1844 different kinds of chorographies of the Ming and Qing dynasties and other related historical books, 1401 notes which recorded the sand-dust weathers occurring on North China Plan from 1443 to 1913 were collected and sorted out. Based on these historical notes, the temporal distribution curve of the sand-dust weathers during this period was carefully reconstructed and analyzed. Analysis on the temporal distribution shows that the sand-dust weathers happened on North China Plain in historical time mainly concentrated in spring. About 71% of sand-dust weathers occurred in spring, 18 % in winter, 9 % in summer, and 2 % in fall. April had the highest amount of sand-dust weathers in a year, accounting for about 30% of the total. The frequency of the annual sand-dust weather curve fluctuated without obvious upward or downward tendency, but it did show periodicity to some degrees. From the period 1500 to 1700, there existed about 30 year's cycles, and from 1700 to 1913, there existed about 50 year's cycles. This temporal distribution of the sand-dust weathers had little relationship with human action, but controlled by natural factors. Comparson of the temporal distribution curve of sand-dust weathers with the curves of mean 10 years spring-winter temperature and mean annual precipitation in the North China Plain in the same period indicated that the occurrence of the sand-dust weathers had significant negative correlations with the mean annual precipitation curve and the mean spring-winter temperature curves. The time periods which had more precipitation usually respond to descending of the sand-dust weathers, whereas the periods of less precipitation respond to increasing of the sand-dust weathers. The lower temperature periods in spring-winter season, which generally had close relationship with the higher wind occurrence, usually had higher occurrence frequencies of the sand-dust weathers.