STUDY OF THE LARGE EXTENT FLOODING OVER EASTERN CHINA IN 1823 AS ONE OF THE EXTREME CLIMATIC EVENTS IN HISTORY
历史极端雨涝事件研究——1823年我国东部大范围雨涝

Disastrous floods happened in 1823 to more than one river valley over Eastern China and they were serious meteorological and extreme climatic event in the cold background of Little Ice Age.In this paper the rainy and flood situation in 1823 is reproduced by means of historical literature records,and the weather character,accompanied disasters,societal impact and the external affecting factors in this year are discussed.In 1823 the North China had suffered prolonged rainy season with multiple torrential rains; over the mid to lower basin of the Yangtze by persistent precipitation in spring to autumn; in South China by abundance in rains in summer-autumn,leading to rainstorms-caused calamities in the drainage areas of the Haihe,Huanghe,Yangtze,Pearl River etc,with these regions suffering heavy rains and flash floods and the beginning/ending dates of rainy spell for 8 places drawn on maps,indicative of the rain belt be progressively moving from south to north comply with seasonal change.It is discovered that >40-day heavy rains in the summer of 1823 were recorded in Beijing,Tianjin and part of the Hebei Province.June~August rainfall in Beijing was 633mm,210mm higher compared to the mean over 1971~2000,equivalent to nearly 50%increase,and the number of rainy days of 53 d.was 17.7 d.more than the mean over 1971~2000 at the same interval,the figure being bigger in excess of 50%.Floods over the North China plains in 1832 were produced by burst banks of Rivers Hutuo,Zi,Hun,Zhang,Luo,Luan,Wei and Ziya,to name but a few.For the lower Yangtze Basin,burst banks of rivers and damaged coasts of lakes caused low-land to be flooded for 4months or more,a situation that was more serious in comparison to the 1804 case.The 1823 precipitation and floods gave rise to large-scale crop production drop and even entire harvest failure.As a result of the rainfall and floods,temperature was low enough in the lower basin of the Yangtze to give poor harvest of paddy rice and absolute failure of cotton,leading to their soaring prices to result in famine in many regions,and corresponding relief was carried out by the governments.And epidemic occurred over provinces of Hebei,Shanxi,Liaoning(in the north),Hunan,Fujian,Guangdong,Guangxi and Yunnan(in the south of the country)in this year.The year of 1823 was characterized by low temperature and actively cold air masses,heavy snowfalls in the spring,long spells of rainy weather and cool temperature in the summer,early frost in the autumn and heavy snowfall and freezing rains in the winter,with the rainy season starting earlier,persisting long enough and marked by high intensity.These synoptic and climatic aspects of 1823 were extremely similar to those of 1954 the severest flood year of 20th century.As for the external affecting factors,both cases taking place in the minimum-value phase of the solar activity period and 1~2 years after ending the moderate-intensity El Ni o event.