石羊河流域负积温的时空演变特征

利用1960—2017年石羊河流域5个气象站逐日平均气温资料,计算了各地年负积温,并运用线性趋势系数法、方差分析周期法、累计距平和信噪比法以及相关系数法,分析了石羊河流域负积温的时空分布特征及负积温与气温和冻土的关系。结果表明：受海拔高度、地形地貌、植被覆盖和天气系统的影响,石羊河流域负积温具有明显地域特征,负积温平均和极值为绿洲平原区高于荒漠区,荒漠区高于山区。负积温正常年份最多,概率在60%以上,依次向两端迅速递减。年、年代负积温总体呈升高趋势,古浪升高趋势最明显。年负积温的时间序列存在7～9 a的准周期变化,古浪负积温在1986年发生了气候突变,其他各地没有发生气候突变。各地负积温初日、终日、负积温期有一定的差异,最早负积温初日(2003年8月15日)和最迟负积温终日(1986年6月26日)均出现在天祝,负积温期最长258 d(1972年)在天祝,最短100 d(2001年)在民勤。石羊河流域年负积温与年气温呈极显著正相关,负积温的升高与年温度的上升具有较好的同步性。石羊河流域冻土的变化对负积温的响应敏感,负积温每升高100 ℃,冻土日数减少6.2 d,平均冻土深度减小4.5 cm,最大冻土深度减小6.9 cm。

Spatial and Temporal Evolution Characteristics of Negative Accumulated Temperature in Shiyang River Basin

Using daily average temperature of five meteorological stations in Shiyang River Basin from 1960 to 2017, we analyzed spatial and temporal distribution characteristics of negative accumulated temperature and its relationship with temperature and frozen soil by linear trend coefficient method, ANOVA cycle method, accumulative anomaly and signal-to-noise ratio method. The results showed that the negative accumulated temperature of Shiyang River Basin was affected by altitude, landform, vegetation and weather system, and had obvious regional characteristics, the average and extreme value of the negative accumulated temperature was the highest in oasis plain, followed by that in desert area and mountain area. The negative accumulated temperature of normal years was the most, the probability was over 60%, and declined rapidly to both ends. The annual and decadal negative accumulated temperature showed increasing trends, and the increasing trend was the most obvious in Gulang. Time series quasi-period of the annual negative accumulated temperature was 7-9 years. The negative accumulated temperature in Gulang had an abrupt change in 1986, and there was no abrupt climate change in other regions. The starting and ending date and the emergence period of the negative accumulated temperature had certain differences, the earliest starting date (September 2, 1972) and the latest ending date (June 9, 1969) of the negative accumulated temperature all appeared in Tianzhu. The longest negative accumulated temperature period was 258 d (1972) in Tianzhu and the shortest was 100 d (2001) in Minqin. There was a very significant positive correlation between annual negative accumulated temperature and annual temperature in Shiyang River Basin, and the rise of the negative accumulated temperature had a good synchronous with annual temperature. Response of frozen soil change to the negative accumulated temperature was sensitive in Shiyang River Basin, with the increase of the negative accumulated temperature of 100°C, the frozen soil days decreased by about 6.2 d, the average frozen soil depth decreasesd by 4.5 cm and the maximum frozen soil depth decreased by about 6.9 cm.