近60 a来西秦岭及周边地区降水的分布格局

基于西秦岭及周边地区15个气象站点的降水、气温等月值、年值资料,采用相关统计分析及检验的方法,研究了1951年以来该区域近60 a干湿变化的时空特征。结果表明:西秦岭及周边地区1951年以来降水量呈下降趋势,秋季降水量减少趋势最明显,速率为-18.6 mm· (10 a)^-1;而近60 a年平均气温呈上升趋势,升温速率为0.28℃· (10 a)^-1。对比气温和降水要素,西秦岭及周边地区年平均温度每升高1℃,则年降水减少37 mm,表明该区近60 a由冷湿向暖干转变。同时将气候要素与Niño3.4指数进行相关分析,结果显示在厄尔尼诺事件发生当年该区降水少,气温高,容易发生干旱。利用改进的经验正交函数法分析西秦岭及其周边地区15个气象站点的气候要素,发现该区年降水距平百分率的第一模态解释方差为49.0%,整个区域呈同向变化,而年平均温度距平第一模态解释方差为78.8%,在整个区域内亦呈现同向变化。对比两个要素第一模态显示西秦岭近60 a东部地区与西部地区相比,呈现降水减少幅度大,气温升高速率小的分布格局。

Spatial and temporal patterns of precipitation in the west Qinling over the past 60 years

West Qinling Mountains is located to the east edge of the Tibetan Plateau and in the monsoon fringe area, its climate is affected by the thermal effects of Tibetan Plateau and is very sensitive to the monsoon variability. However, the spatial and temporal characteristics of precipitation in West Qinling over the past 60 years are still unclear. Based on the instrumental monthly precipitation and temperature in 1951-2014 of 15 meteorological stations in West Qinling Mountains and the surrounding areas, the temporal and spatial characteristics of wet and dry spells over the past 60 years are analyzed using the relevant statistical analysis, the non-parametric tests and the improved empirical orthogonal function method. The results show that the precipitation has a downward trend in the West Qinling Mountains and the surrounding areas since 1951. The autumn precipitation the most significant downward trend than that of the other seasons, with -18.6 mm· (10 a)^-1. Moreover, the temperature has an upward trend with 0.28℃· (10 a)^-1 over the last 60 years. The temperature incre-ased 1℃, while the precipitation decreased 37 mm at the study area. Compared with the Niño3.4 index, the study area has less precipitation and high temperature, and tends to drought at the EI Niño year. Through the empirical orthogonal function analysis(EOF), the variance of the precipitation is explained by the EOF1 with 49.0%, and the EOF1 of the temperature explained 78.8% total variance. Two patterns all display consistency changes in whole West Qinling regions, and the eastern West Qinling have larger precipitation decreased rate and smaller temperature increased rate than that of the western. These results fill the gaps in the regional precipitation research in West Qinling and provide a reference for understanding the climate change in the monsoon marginal areas.