【摘要】 利用1961～2005年中国565个台站的逐日降水量观测资料,运用线性回归等统计方法对我国夏季(6～8月)降水进行了日雨量分级研究。按日雨量大小依次分成痕量(无记录)、微量(≤1 mm/d)、小雨(1.1～9.9 mm/d)、大雨(10～49.9 mm/d)、暴雨(50～99.9 mm/d)和大暴雨(≥100 mm/d)6个等级,而把小雨～大暴雨4个等级的雨日量总和称为有效雨日。年平均痕量雨日东西差异以东亚夏季风气候北缘为分界线,该线以西地区痕量雨日数大于以东地区。有效雨日的分布表现为西北地区最少,东部地区从西南至华南地区依次向北递减,其中东北地区东部的雨日数要大于西部。近45年来有效雨日的趋势分布表现为长江流域中下游、西北地区的新疆等地雨日增加,而黄河中下游等地区雨日减少。痕量雨日在我国基本为负趋势。微量雨日除我国西北地区为正趋势以外,其他地区均为负趋势。西北地区有效雨日增多主要来自于小雨雨日的贡献,长江-江南的有效雨日增多来自于大雨和暴雨雨日的贡献。西南和环渤海地区的有效雨日减少来自于大雨雨日的减少。更多还原

【Abstract】 Based on the daily rainfall dataset of 565 stations for the period of 1961～2005, graded summer rain days are investigated using the linear regression method. The precipitation amounts are classified into six grades or intensities according to daily precipitation rates, namely, trace (no amount), slight(≤1.0 mm/d),small(1.1 ～ 9.9 mm/d), large(10.0 ～ 49.9 mm/d), heavy(50.0 ～ 99.9 mm/d), and huge( ≥ 100 mm/d) precipitation. Together, the last four grades constitute to a so-called effective precipitation(≥1.0 mm/d). The geographical characteristics for each graded rain day are identified. The results show that the spatial distribution of trace precipitation day is separated by the Northernmost boundary of the East Asian Summer Monsoon with more rain days in the west part of China. The number of efficient precipitation day is the least in Northwest China and it gradually decreases from South and Southwest China to North China. According to the results of rain day trends, the efficient precipitation day increases in the Yangtze River valley and Northwest China such as the Xinjiang Region, but a decreasing trend is found in the Yellow River Valley. The trace precipitation day shows a negative trend in most parts of China. The positive trend of efficient precipitation day in Northwest China is mainly attributed to the small precipitation days, while it is mainly contributed by large and heavy precipitation days in Yangtze River Valley and the area between lower reaches of the Yangtze and Huaihe River valleys. The negative trends of efficient precipitation day over Southwest China and region on the rim of the Bohai Sea are mainly resulted from large rain days.更多还原