近50年华北地区极端气候分析
Climate extremes for agriculture-pasture transitional zone, northern China, are analyzed on the basis of daily mean temperature and precipitation observations for 31 stations in the period 1956-2001. Analysis season for precipitation is May-September, i.e., the rainy season. For temperature is the hottest three months, i.e., June through August. Heavy rain events, defined as those with daily precipitation equal to or larger than 50 mm, show no significant secular trend. A jump-like change, however, is found occurring in about 1980. For the period 1980-1993, the frequency of heavy rain events is significantly lower than the previous periods. Simultaneously, the occurring time of heavy rains expanded, commencing about one month early and ending one month later. Long dry spells are defined as those with longer than 10 days without rainfall. The frequency of long dry spells displays a significant (at the 99% confidence level) trend at the value of +8.3%/10a. That may be one of the major causes of the frequent droughts emerging over northern China during the last decades. Extremely hot and low temperature events are defined as the uppermost 10%daily temperatures and the lowest 10% daily temperatures, respectively. There is a weak and non-significant upward trend in frequency of extremely high temperatures from the 1950s to the mid-1990s. But the number of hot events increases as much as twice since 1997. That coincides well with the sudden rise in mean summer temperature for the same period. Contrary to that, the frequency of low temperature events have been decreasing steadily since the 1950s, with a significant linear trend of-15%/10a.
作 者： 韩晖 龚道溢 HAN Hui GONG Daoyi 作者单位： 韩晖,HAN Hui(Key Laboratory of Environmental Change and Natural Disaster,Institute of Resources Science,Beijing Normal University,Beijing 100875,China)龚道溢,GONG Daoyi(Key Laboratory of Environmental Change and Natural Disaster,Institute of Resources Science,Beijing Normal University,Beijing 100875,China;Bjerknes Centre for Climate Research,University of Bergen,Norway)
刊 名： 地理学报(英文版) ISTIC SCI 英文刊名： JOURNAL OF GEOGRAPHICAL SCIENCES 年，卷(期)： 2003 13(4) 分类号： P461 关键词： agriculture-pasture transitional zone climate extremes trends