陕西黄土高原近50年日照时数的变化

Variation of Sunshine Hours over Loess Plateau of Shaanxi in Recent 50 Years

[目的]研究陕西黄土高原1961～2010年日照时数的变化特征。[方法]基于陕西黄土高原43个台站1961～2010年逐月日照时数,采用气候倾向率、气候趋势系数、Mann-Kendall分析、小波分析和线性相关等方法,对近50年陕西黄土高原日照时数的时空变化特征进行分析,并探讨了引起该区域日照时数变化的主要原因。[结果]近50年来,陕西黄土高原年日照时数呈减少趋势,气候倾向率为-14.47 h/10a。除春季日照时数表现为增加趋势外,其他季节均表现为不同程度的减少趋势。其中,以夏季减幅最显著,平均减少24.34h/10a。陕西黄土高原年、季日照时数气候趋势系数呈上升趋势的区域主要分布在米脂、子洲、绥德、延安、延长和安塞,其余区域为下降趋势。近50年来,陕西黄土高原年日照时数在1972和2003年发生突变,并存在5～7年的振荡周期。近年来,大气污染严重,混浊程度加大,从而增强了大气对太阳光的反射及吸收作用,使太阳辐射减小,由此造成年日照时数减少。[结论]该研究为分析陕西黄土高原的气候变化提供了依据。

[Objective] The research aimed to study variation characteristics of sunshine hours over Loess Plateau of Shaanxi during 1961-2010.[Method] Based on the monthly sunshine hours at 43 stations over Loess Plateau of Shaanxi during 1961-2010,by using the climate tendency rate,climate trend coefficient,Mann-Kendall analysis,wavelet analysis and linear correlation,the temporal and spatial variation characteristics of sunshine hours in Loess Plateau of Shaanxi in recent 50 years were analyzed.Moreover,the main reason for inducing variation of sunshine hours in the zone was discussed.[Result] The annual sunshine hours in Loess Plateau of Shaanxi in recent 50 years presented decrease trend,and the climate tendency rate was-14.47 h/10 a.Except in spring,the sunshine hours all presented decrease trend at different degrees in other seasons.The most significant decrease amplitude（-24.34 h/10 a） occurred in autumn.The zones where the climate trend coefficients of annual and seasonal sunshine hours presented rise trend in Loess plateau of Shaanxi mainly appeared in Mizhi,Zizhou,Suide,Yanan,Yanchang and Ansai.The other areas had decrease trend.The annual sunshine hours in Loess plateau of Shaanxi in 50 years had two mutation points in 1972 and 2003,and had oscillation period of 5-7 years.In recent years,the atmospheric pollution was serious,and the turbid degree increased.Then,the reflection and absorption effects of atmosphere on sunlight were strengthened.The solar radiation decreased,and the annual sunshine hours decreased.[Conclusion] The research provided basis for analyzing climate variation over Loess Plateau of Shaanxi.