华北地区高温日数的气候特征及变化规律

Climatic Characteristics and the Spatio-temporal Variation of High Temperature Days in North China in 1960-2009

基于1960～2009年华北地区90个台站逐日最高气温数据,采用趋势分析等方法分析近50 a华北地区高温日数的时空变化特征。结果表明,近50 a华北地区高温日数以海拔高度800 m等值线为界呈现南多北少的分布特点,南部主要呈减少趋势,北部主要呈增加趋势。同时它显现出明显的"多-少-多"年代际变化特征,与1960年代相比,2000年代高温日数在7月稍增加,5和8月有所减少。近50 a华北地区累计高温过程频次呈微弱的减少趋势,南北部高温过程集中的年代和月份也有所不同。

Based on the daily maximum air temperature data from 90 meteorological stations in the period 1960-2009, the climatic characteristics and the spatio-temporal variation of high temperature days （HTDs） in North China were analyzed by using the statistical methods including trend analysis. The results show that the HTDs are more in the south and less in the north on conditions that 800-meters elevation contour serves the boundary. There exist two high value centers, which is located in the south of Hebei Province and the regions from southwest of Shanxi Province to Zhengzhou and Xuchang of Henan Province respectively. The most an- nual mean HTDs reach 25.7d, which occurs in Yuncheng of Shanxi Province. The HTDs are mainly on the de- crease in the south of North China and on the increase in the north. The most obvious decrease in HTDs occurs in Kaifeng of Henan Province and the linear trend is -2.8d/10a. The most obvious increase in HTDs occurs in Hequ of Shanxi Province and the linear trend is 1.5 1d/10a. The HTDs in recent 50 years has a distinct decadal evolution of increasing-decreasing-increasing. The high temperature mainly occurs during May to August, es- pecially in June and July. Compared with the HTDs in the 1960s, those in the 2000s are slightly on the increase during July and on the decrease during May and August, The accumulated high temperature process （HTP） is on the detectable decrease, while the moderate HTP is on the detectable increase. As far as the HTP lasting day number mor6 than 5 days is concerned, the number in Beijing is less than Erenhot and the number in Zheng- zhou is 3.3 times as many as that in Beijing. There exist some difference in the era and month of HTP between the south and the north.