河套凌汛时期气温演变特征

Evolvement of Temperature at the Bend of the Yellow Rive during Freeze Phase

利用49a(1955-2003年)河套封冻期日气温资料,采用小波分析等方法,研究了该区域在近47a的气温、气温差、负积温的变化。结果表明:黄河甘肃内蒙古段冬季气温存在明显线形上升趋势,平均速度在0.42℃/10a^1.06℃/10a之间;兰州-银川段气温差减小,银川-包头段气温差加大;负积温时间变化呈明显下降趋势,线性变化率为-8.88℃/a。负积温演变在1986年附近发生了突变,负积温量突变性减少;稳定低于0℃的开始日期和结束日期存在明显的线性变化趋势,开始日期平均以1.6d/10a速度推迟,结束日期平均以2.2d/10a速度提前,负积温时段长度呈明显线性减少;负积温变化存在2a^4a、5a左右的年际振荡,1986年突变前振幅较大,突变后振幅减弱,5a周期消失。

By applying the wavelet analysis on temperature data during 1955 - 2003 to display the eharactersisties of region, the spatial and temporal variations of temperature of the bend of the Yellow River, winter temperature, negative total temperature and temptrature difference were studied. The results showed that the temperature in winter had an obvious linear trend of escalation, with the velocity between 0.42 ℃ / 10a and 1.06 ℃ /10a, in the Yellow River from Gansu to Inner Mongolia. The difference of temperature became small from Lanzhou to Yinchuan, but got enlarger between Yinchuan and Baotou. The total negative total temperature descended, with a velocity -8.88℃ as annually, had remarkably 2 phases divided by a jump-point, in 1986, by the moving t-text. The negative total temperature adapted to reduce after the jump-point. By using the wavelet analysis, 2 - 4 and 5 years variation period, the 2 - 4 years period stands out. The amplitude of temperature waves was strengthed in negative one before jump point; after in positive one, 2 -4 year period became weakened, 5 years period disappeared. The begin day of negative temperature retarded 0.16 day in annual; the end day of one moved up 0.22 day annually.