南宋以来太湖流域大涝大旱及近期趋势估计

THE HEAVY FLOOD AND DROUGHT OF TAIHU BASIN FROM THE SOUTHERN-SONG DYNASTY AND THE POSSIBI- LITY OF THEIR RECURRENCE IN THE NEAR FUTURE

本文研究南宋以来太湖地区大旱大涝并对近期大旱大涝趋势作了估计。

During the Southern-Song Dynasty, the Taihu basin was the political, economical and cultural center of China, therefore there are many historical events about climate. In this paper, on the basis of these accumulated data, the flood and drought order sequence of Taihu basin during the last 863 years (1121-1983 A.D.) has been built. It consists of nine orders. In addition, the heavy flood and drought that have happened since the southern song Dynasty was studied by the sequence analysis method. Furthermore, according to the statistical theory of extreme values, the possibility of their recurrence in the near future was estimated.The main conclusions are as follows;1. From Nan-Song dynasty, the flood years were a little more than drought years and normal years. Their proportion was 4 :3 : 3. In flood and drought years, the gentleness was most, the gentleness and the normal years account for over 60% of the total, the very heavy account for about 3%.2. The flood years were relatively concentrated in the 14th and 15th century; the drought years were relatively concentrated in the 13th and 16th century and after the 18th century the proportion of very heavy flood and drought years has been increased obviously, among the flood and drought years.3. Most of heavy flood and drought in history occurred in summer and autumn. Numerous successive years of flood and drought was one of the remarkable characteristics of heavy flood and drought. The successive years of flood and drought were resulted in the extreme cases of flood and drought in history4. By 1994, it will be probable that one very heavy flood (similar to that of 1954) , one or two heavy flood (similar to that of 1980) and one heavy drought (similar to that of 1968)will occur, but there is little possibi lity of occurring of very heavy drought, in general.