1823年太湖流域极端雨涝事件的重建和特征分析

RECONSTRUCTION AND CHARACTERISTIC ANALYSIS OF THE EXTREME FLOODING EVENT IN THE TAIHU LAKE BASIN IN 1823

清道光三年（1823年）太湖流域发生了严重的雨涝灾害。利用《管庭芬日记》保存的降水信息复原了海宁地区逐月降水量，进而综合日记、档案和地方志中天气、雨情、水情、灾情等记录系统梳理太湖流域由春至秋的降水过程、水位变化和水灾分布特征，并探讨此次大涝的天气气候背景。主要得到以下结论：1）该年太湖流域雨期长，集中降水始于2月16日，到9月22日才基本结束，流域由春至秋大致经历10次降水集中期和10场暴雨过程。海宁汛期5月、6月、7月、9月雨日和雨量尤多，较平湖地区1954～2009年分别增加52．2％～72．7％和100．5％～321．5％，5月、汛期和年降水量重现期均达到200年一遇。2）本年的梅雨期相对典型，海宁6月7日入梅，较常年提前8天，春雨梅雨无明显间歇；7月4日出梅，梅期雨日23天，梅期长27大，梅雨量571．9mm，梅雨降水异常偏强，期间至少有3场暴雨过程。3）流域汛期水位历经3次显著上涨阶段，8月7～14日台风暴雨期间太湖以东地区水位普遍达到峰值，吴江地区洪水位估算为4．38m，接近1954年和1999年最大值。4）水灾持续约4个月，主要分布于流域中东部低平原区，以阳澄淀泖区、东苕溪一带灾情最重，雨带长期维持、梅期降水异常偏强、台风接连入侵和太湖下泄水道年久淤塞致使排涝功能萎缩是流域性大涝的重要原因。5）流域1822／23年冬季、春季早期气温与常年相仿，但期间天气复杂多变，气温冷暖波动频繁，春季后期温度偏低。

Disastrous floods happened in the Taihu Lake basin in 1823. This paper reconstructs the monthly precipitation according to the rainy information recorded in the diary named Guan Tingfen Diary in Haining area in 1823. Moreover, characteristics of the precipitation concentration period, water level change process and flood distribution in Taihu Lake basin from spring to autumn are reproduced systematically by means of the weather information, rainy condition, water level situation and disaster situation recorded in diaries, archives and local chronicles. Lastly we analyse the weather and climate background about this flood. Main results are as follow. （1） Taihu Lake basin has suffered prolonged rainy season in 1823, and continuous rainfall was from February 16th to September 22nd. There are approximately 10 precipitation concentration periods and 10 rainstorm processes in the Taihu Lake basin in the year of 1823. The rainfall days and precipitation in Haining in May, June, July, and September of 1823 were especially more than the mean over 1954-2009 in Pinghu, with the rainfall days increase by 52.2% -72.7% and the precipitation increase by 100.5% - 321.5%. Reappearing period of the precipitation in May, flood season, and the year all reached to 200 years. （2） The type of Meiyu in 1823 was relatively typical. The starting date of Meiyu in Haining was June 7th, which was 8 days earlier than the average date, leading to indistinct interval between spring rain and Meiyu, the ending date was July 4th, the rainfall days was 23, the duration days was 27, and the precipitation was 571.9mm. The intensity of rainfall in Meiyu was unusually strong, with at least 3 rainstorm processes. （3） There were 3 obvious rising stages for the water level in the Taihu Lake basin in flood season, and the water levels in eastern regions of Taihu were universally at maximum value when two typhoons occurred during August 7th to August 14th. It is estimated the flood-peak in Wujiang area was 4.38m that was approaching to the level of the year of 1954 and 1999. （4） This flood caused low-land to be submerged for 4 months or more, mainly distributed in the low plains in the middle and eastern parts of the Taihu Lake basin, with the extremely serious band along the areas of Yangcheng Lake and Dianshan Lake as well as the eastern section of Tiaoxi River. The important factors of this flood could be attributed to persistent rain belts, multiple torrential rains in Meiyu, successive invasion of two severe typhoons and the river drainage system paralysis because of increasingly massive sediments. （5） The temperature in winter and early spring in 1822/23 were close to present average, but the weather in this period was complicated, with frequently fluctuant temperature, and the temperature in late spring was lower.