１９９８年长江中下游地区发生继１９５４年以来特大洪灾，究其原因有以下几点：１．天气和气候原因１９９８年大气环流异常造成的洪涝天气形势是：①４月—５月，太平洋暖湿气团逐渐强盛，与较强的变性极地气团交锋于南岭山脉北坡，呈半静止状态，造成连阴雨天气；②６月... In 1998, the following large floods occurred in the middle and lower reaches of the Yangtze River since 1954, for the following reasons: 1. Weather and Climatological Conditions The flood situation caused by the abnormal atmospheric circulation in 1998 was: ① From April to May, warm and humid air masses in the Pacific gradually became stronger and stronger, confronted with strong degenerate polar air mass clashes on the northern slope of the Nanling Mountains, resulting in a semi-quiescent state Even the rainy weather; ② June ...