长江中、下游特大暴雨洪水的成功预报和科学依据

THE SUCCESSFUL FORECAST OF THE TORRENTIAL RAIN AND FLOOD OVER THE MID-LOWER REACHES OF THE YANGTZE RIVER AND ITS SCIENTIFIC BASIS

进入 2 0世纪 90年代以来 ,中国七大江河流域旱涝频繁 ,旱涝灾害和由旱涝引起的次生地质灾害十分严重 ,特别是长江中、下游地区的洪涝几率高达 5 0 % (5 /10 )。 195 1— 2 0 0 0年长江中、下游地区发生了 9个大水年 ,几率为 18% (9/5 0 ) ,90年代洪涝的频繁程度属 2 0世纪之最 ,1998年特大暴雨洪水的时空集中强度也属 2 0世纪之最。长江的大暴雨洪水在近 10a来很频繁 ,但从气候分布几率来看 ,它毕竟是小概率事件 ,对小概率事件的长期预报具有很大的难度 ,而且暴雨洪水的长期影响因子也错综复杂 ,这就给预报带来了艰巨性。通过对降水的各种影响因子的分析研究和多因子集成预报模型的研制 ,对 1998年长江流域的特大暴雨洪水从时间、地区和量级三要素的长、中期预报都取得了成功 ,对其他 5个洪涝年也从趋势和分级两方面做出了成功的长期预报。文中重点剖析了预报取得成功的科学依据。

Since 1990s, occurrence of drought/flood over the seven big river valleys in China is of high frequency. Drought/Flood disasters and geological disasters are very frequent. Especially, flood probability in the mid\|lower reaches of the Yangtze River is up to 50 %.There have occurred nine severe flood years in the mid lower reaches of the Yangtze River during 1951 to 2000, and the probability is 18%.In 20 century, the space time intensity of torrential rainstorm in 1998 is the most severe. Torrential rainstorms and floods over the Yangtze River are very frequent during the recent 10 years. However, according to the probability of climatic distribution the rainstorm and flood is the small probability affair after all, and the long term forecast of the affair is very difficult. Additional, due to the complexity of long term effecting factors of torrential rain and flood, the forecast becomes more difficult. By analysing and studying all kinds of rain factors, and developing the assembly model of forecast, the successful mid and long term forecast of the torrential rainstorm and flood was carried out on their intensity and spatial and temporal distribution over the Yangtze River in 1998. As to the other five flood years, the successful long term forecast was made on their tendency and level. In this paper, an analysis on the scientific bases which attributes to the successful forecast was made.