甘南白龙江流域光照资源的气候变化特征

光照资源的变化会对气候和生态环境产生较大的影响。利用1973-2012 年甘肃甘南白龙江流域近40 a 日照时数观测资料，采用气候倾向率等现代统计诊断方法，对甘南白龙江流域光照资源的变化趋势、气候突变等特征进行了分析，结果表明：甘南白龙江流域日照时数呈现出显著增加的趋势，其增幅为33.0 h/10 a，各季节日照时数都呈增加的趋势，其中以春季增幅最明显，夏季最小。这与中国大部分地区日照时数呈现显著减少的特征不同，体现出甘南白龙江流域独特的气候特点及日照时数变化的复杂性。甘南白龙江流域日照时数在1994 年之前以负距平变化为主，1994 年及其之后以正距平变化为主，为光照资源偏多期。甘南白龙江流域年平均日照时数及各季节平均日照时数均发生了增多突变。1983 年为年平均日照时数的增多突变起始年。夏季平均日照时数增多突变发生在20 世纪90 年代末，其余各季平均日照时数增多突变均发生在80 年代。年日照时数异常偏少年份主要发生在20 世纪80 年代，异常偏多仅出现在2002 年。在气候变暖的背景下，甘南白龙江流域≥0.1 mm降水日数的减少可能是引起日照时数增加的主要原因。日照时数与气温、蒸发量均呈显著的正相关。三者在变化趋势上有着很强的一致性。

Climatic Change of Sunshine Duration in the Bailong River Valley in Gannan from 1973 to 2012

Change of sunshine duration affects climate and eco-environment greatly. Using the modern statistical methods such as linear trend and abrupt change analysis, the recent 40 years (1973-2012) sunshine duration changing trend and abrupt change in the Bailong River Valley in Gannan were analyzed. The results showed that the average annual sunshine duration in the Bailong River Valley in Gannan increased significantly in recent 40 years with an increasing rate of 33.0 h/10 a. The seasonal sunshine duration showed different increasing rates,which was the largest in spring and the smallest in summer. This phenomenon was different from those occurred in most of China with a decreasing trend of sunshine duration, and reflected the unique characteristics of climate anomaly and complexity change in sunshine duration in the Bailong River Valley in Gannan. The average annual sunshine duration anomaly was negative before 1994 and positive after 1994 in the Bailong River Valley in Gannan. The average annual sunshine duration as well as seasonal sunshine duration showed abrupt increase. The average annual sunshine duration presented abrupt increase in 1983, the summer sunshine duration increased abruptly in the 1990s, and increased abruptly in other seasons in the 1980s. Meanwhile, the annual sunshine duration of less anomalous years occurred in the 1980s while more anomalous years occurred only in 2002. Under background of the climate warming, the rainy days with over 0.1 mm precipitation per day decreased in the Bailong River Valley in Gannan, which was a primary cause for the increases of sunshine duration. Sunshine duration, temperature and evaporation showed a significant positive correlation and shared a strong consistency in the changing trend.