1998年长江流域暴雨洪水环流背景分析

１９９８年主汛期，由于西太平洋副热带持续偏南、偏强，中高纬度维持稳定的阻塞形势，６、７月雨带长期在鄱阳湖、没庭湖地区徘徊，造成长江中下游地区严重洪涝；８月随着副高北抬，长江上游出现多次强降水过程，长江干流受中下游洪水顶主上游洪峰下泻的影响，水位居高不下，多数水文站出现了超记录的历史最高水位。１９９８年的已成为一次少有的新的长江大洪水的典型。

Analysis on weather background for 1998 heavy flood in the Yangtze River Valley

In the main flood season in 1998, the west Pacific subtropical high was deviated to the south and was much stronger than usual for a long time, and stable blocking pattern was persistent in the middle and high latitudes in the Northern Hemisphere. As a result, the rain belt paced up and down over Dongting and Poyang Lake water systems during June and July, which led to severe flooding in the middle and lower Yangtze River. In August, with the subtropical high migrating to the north and the west, heavy rain processes occurred in the upper Yangtze. Due to the fact that the peak floods from the upper reaches were rushing downstream and the floods on the middle and lower reaches were jacked up, flood stages on the main stem remained high for a long time. Flood stages at most hydrometrical stations on the main stem exceeded the corresponding historical records. The 1998 flood was a new type of heavy flood on the Yangtze River.