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受东亚大气环流异常影响，１９９８年从５月中旬末开始，内蒙古自西向东先后进入汛期，汛期开始较往年提前近１个月，而且持续时间较长，汛情十分严峻。基于全区各台站历年汛期降水数据的统计分析和１９９８年降水的时空分布情况及其与历年的比较分析，今年的汛期可以划分为４个阶段：（１）５月中旬末至下旬，我区西部降大～暴雨，发生洪灾；（２）６月中旬至７月中旬，我区大部普降中～大雨、局部暴雨，中部发生洪涝灾害；（３）７月下旬至８月中旬，东部多次降大～暴雨，洪涝灾害异常严重；（４）８月下旬全区降雨渐少，汛情日缓。
Affected by the anomalous atmospheric circulation in East Asia, Inner Mongolia started its flood season from west to east in 1998 at the end of mid-May 1998, with the flood season starting nearly 1 month earlier than in previous years and with a relatively long duration. The flood was very severe. Based on the statistical analysis of the rainfall data of all stations in the whole region in the past years and the temporal and spatial distribution of precipitation in 1998 and their comparison with the past years, the flood season of this year can be divided into four phases: (1) From late to late mid-May (2) From mid-June to mid-July, most of the area has heavy rain, heavy rainstorms and floods in central China; (3) From late July to mid-August, In the eastern part of the country, heavy rainstorms were reduced several times and floods and catastrophes were extremely serious. (4) Rainfall in the whole region was gradually reduced in late August, and floods were easing.