中国北方近50年温度和降水极端事件变化

Change in Extreme Temperature and Precipitation over Northern China During the Second Half of the20th Century

利用中国近50年逐日最高、最低气温和降水资料,计算分析北方极端高温、极端低温和极端强降水事件的频率变化趋势。研究结果表明,中国北方夜间温度极端偏低的日数显著趋于变少;白天温度偏高的日数则趋于增多,只有华北南部例外。同时我国北方日最低气温小于0℃的日数显著减少,这使得我国北方,尤其是东部地区无霜期明显加长。从降水来看,华北地区强降水事件趋于减少,但西北地区强降水事件趋于增多。

Study on change of weather and climate extremes has become an important aspect inmodern climate change research. Based on the daily surface air temperature data from 200 stations and daily precipitation data from 739 stations during the second half of the 20th century, schemes for analyzing climate extremes were designed mainly according to percentiles of a non-parametric distribution and the gross errors in the daily data were removed based on a newly designed quality control procedure. The spatial and temporal characteristics of change of climate extremes over northern China were studied. The main conclusions are summarized as follows: 1) The number of days with maximum temperatures over 35 o C decreased slightly. The decreasing trends are obvious in the North China Plain and the Hexi Corridor. However, since the 1990s, the extreme hot days increased greatly. Meanwhile, the frost days decreased significantly in northern China, especially in the eastern part of northern China and Xinjiang Uygur Autonomous Region. Increase trends were found for the 95th percentiles of daily maximum temperatures except in the southern part of North China, while obvious decrease trends were found for the 5th percentiles of daily minimum temperatures. 2) The extreme intense precipitation events obviously increased in much of northwestern China but decreased in the eastern part of northeastern China and most parts of North China. The number of heavy rain days increased in eastern Inner Mongolia and eastern Northeast China, but obviously decreased in the Northeast China Plain and North China.