Variations of temperature and precipitation extremes in recent two decades over China

Variations of temperature and precipitation extremes were investigated under the rapid warming over China since the 1990s. Six percentile-based indices derived from daily minimum and maximum surface air temperature and daily precipitation amount at 532 meteorological observing stations were computed and compared in two periods of 1960-1989 and 1990-2007. For China as a whole, the occurrence frequencies of annual cold nights and warm nights derived from daily minimum temperature have changed by -3.8% and 2.8% respectively, while annual cold days and warm days derived from daily maximum temperature have experienced relatively smaller variations of -2.1% and 1.8% in recent two decades. Notable frequency decreases of cold extremes were found in North China and Northeast China, whereas warm extremes increased profoundly in South China, Southwest China and Northwest China. Frequency decreases of cold extremes mainly occurred in winter. However, warm extremes displayed both remarkable frequency increases in winter and summer. Meanwhile, annual extreme precipitation amount and extreme precipitation days have separately increased by 10.9 mm and 0.12 days, with significant increases in the mid-lower Yangtze River valley and Northwest China, but only slight variations in Northeast China and North China. Considerable increases were also found in South China and Southwest China yet they were not statistically significant. Precipitation extremes were found largely increased in the rainy season from April to September, thus exhibiting similar spatial patterns to that in annual. As in the dry season from October to next March, significant increases of precipitation extremes were detected in Northeast China and North China instead. (C) 2011 Elsevier B.V. All rights reserved.