【摘要】 该文普查了１９６１—１９９４共３４年长江上、中游地区春季首次大降水的日期及环流形势，得到：春季首次大降水大多出现在４月份；青藏高原以东的低值系统以及来自西伯利亚的冷空气南下补充是导致大降水的两个必要条件更多还原

【Abstract】 The dates and atmospheric circulation patterns of the heavy rain in spring were investigated based on data during 34 years from 1961 to 1994. It is found that the first time heavy rains in spring mostly (about 80%) occur in April;two necessary conditions for the heavy rain are that:the synoptic depression system appears in east of Tibet Plateau and a cold air mass,which moves from Siberia,intrudes into the depression system.更多还原