1961-2005年河西走廊东部极端气温事件变化

Changes in the Extreme Temperatures in the East of Hexi Corridor in 1961-2005

利用1961—2005年河西走廊东部五站的逐日气温资料,通过百分位法定义了不同台站的逐日极端高、低温阈值,研究了河西走廊东部近45a来极端气温事件变化的空间分布以及时间变化特征.结果表明:在空间分布上,河西走廊东部极端最高气温总阈值民勤出现了暖中心,乌鞘岭出现了冷中心;极端最低气温总阈值暖中心出现在武威,冷中心出现在乌鞘岭;极端最高、低气温空间分布与其对应阈值的空间分布类似;河西走廊东部极端低温频数南北部都呈现减少趋势,而极端高温频数在南部古浪和北部靠近沙漠区的民勤呈现减少趋势,其它地区为增加趋势.时间变化上,河西走廊东部极端最高、低气温总体都呈增温趋势,增温幅度极端最低气温比极端最高气温明显;极端最高气温频数总体呈略增加趋势,极端最低气温频数呈明显的减少趋势;极端最高、低气温和极端最高、低气温频数都是6～7a和9～10a周期反映明显;极端最高、低气温增温以及极端高温频数增加和极端低温频数减少都发生了突变现象.

Based on the data of daily temperatures from five weather Stations （Wuwei, Minqin, Yongchang, Gulang, Wushaoling） in the east of Hexi corridor from 1961 to 2005, the thresholds of daily extreme maximum temperatures and extreme minimum temperatures are determined for different stations, and the characteristics of temporal and spatial distributions of extreme temperature events in the east of Hexi corridor are studied for the recent 45 years. The results show that spatially, there are a warm center of extreme maximum temperature threshold in Minqin and a cold center in Wushaoling; there a warm center of extreme minimum temperature threshold in Wuwei and a cold center in Wushaoling. The spatial distributions of the extreme maximum temperature and extreme minimum temperature are similar to those of their thresholds; Frequencies of the extreme minimum temperatures show a decreasing tendency in the south and the north of the east of Hexi corridor, but frequencies of the extreme maximum temperatures show a decreasing tendency in the north of Gulang and near the Minqin desert, with an increasing tendency in other areas. Temporally, the extreme maximum temperature and the extreme minimum temperature show an increasing tendency, with an increase in the extreme minimum temperature more than that in the extreme maximum temperature. Frequencies of the extreme maximum temperature show a slightly increasing tendency, but frequencies of the extreme minimum temperature show an obviously decreasing tendency. It is also found that vibration periods of 6-7 a and 9-10 a are displayed very clearly in the extreme temperatures and the frequencies of extreme temperatures; It is demonstrated that some abrupt changes presented in the series of extreme maximum and minimum temperatures, as well as in the increase of the frequencies of extreme maximum temperature and the decrease of the frequencies of extreme minimum temperature.