1736-2010年华南前汛期始日变化

根据清代华南雨雪分寸记载的内容、特点，参照华南地区前汛期降水特征，提出了利用雨雪分寸记载重建华南前汛期开始时间的方法，重建了1736-1911 年福州与广州前汛期开始日期变化序列；并利用福州与广州（分别始于1953 和1952 年）逐日降水观测记录辨识了器测时期两地前汛期的逐年开始时间；据此分析了过去300 年华南前汛期开始日期的年-年代际变化特征。结果表明：1736-2010 年间，福州、广州两地前汛期开始时间平均为5 月第1 候；但存在显著的年际和年代际波动，其中重建时段（1736-1911 年）的主周期为2~3 年、准10 年和准40年，器测时段的主周期为2~3 年、准10 年和准22 年。在年际尺度，重建时段福州和广州前汛期开始时间最早的年份均为4 月第4 候，最晚的年份则分别为5 月第6 候和6 月第1 候；而器测时段两地前汛期开始时间的最早年、最晚年均为4 月第4 候和6 月第1 候。在年代际尺度，重建时段福州和广州相邻年代最大变幅分别为2.2 候和1.6 候；器测时段福州和广州相邻年代最大变幅则分别为2.5 候和2.4 候。

Variation of starting date of pre-summer rainy season in South China from 1736 to 2010

Based on the documented characteristics of Yu (rainfall)-Xue (snowfall)-Fen (Chinese length unit, 0.32 cm approximately)-Cun (10-Fens) archive in the Qing Dynasty, together with the features of precipitation in pre-summer rainy season in South China, the methods to reconstruct the starting date of pre-summer rainy season in South China was designed. Using the Yu-Xue-Fen-Cun archive, the series of starting date of pre-summer rainy season in Fuzhou and Guangzhou were reconstructed from 1736 to 1911. And the series of starting date of pre-summer rainy season during the instrumental period were identified by daily precipitation records in Fuzhou during 1953-2010 and Guangzhou during 1952-2010. The inter-annual and inter-decadal changes of the starting date for pre-summer rainy season in South China over the past 300 years were analyzed. The results show that the mean of starting date of pre-summer rainy season in South China was the first pentad of May; however there existed obvious inter-annual and inter-decadal variabilities in the starting date of pre-summer rainy season over South China, with quasi-cycles of 2~3 years, 10 years and 40 years during 1736-1911 and those of 2~3 years, 10 years and 22 years during the instrumental periods. The starting date in the earliest year was the fourth pentad of April, while the starting date in the latest year was the sixth pentad of May in Fuzhou and the first pentad of June in Guangzhou during 1736 to 1911; while the starting date in the earliest year and the latest year was the fourth pentad of April and the first pentad of June in Fuzhou during 1953-2010 and Guangzhou during 1952-2010. The maximum magnitude between the adjacent decades was 2.2 pentads in Fuzhou and 1.6 pentads in Guangzhou during the reconstructed periods; while it was 2.5 pentads and 2.4 pentads during the instrumental periods.