Variation of Sunshine Duration and Its Impact Factor in Guoluo Region of Sanjiangyuan

Based on the sunshine data of 6 stations in Guoluo region of Sanjiangyuan from 1980 to 2019, the variation characteristics of sunshine duration and its impact factors were analyzed.The results show that the spatial distribution of sunshine duration in Guoluo region shows a decreasing trend from northwest to southeast.Meanwhile, the sunshine duration decreases significantly at the rate of -40.2 h/(10 a) in recent 40 years.The decreasing trend is found in four seasons of spring, summer, autumn and winter, with a changing rate of -11.4 h/(10 a), -8.2 h/(10 a), -11.8 h/(10 a) and -8.2 h/(10 a), respectively.The distribution of monthly average sunshine duration presents a pattern of “three peaks and three valleys”, and April is the month with the most sunshine duration.Judging by H value of Hurst index, the variation of sunshine duration is consistent with the past, showing a strong decreasing trend, and the variation trend of sunshine duration in four seasons and at all stations is also consistent with the past.There is a significant negative correlation between sunshine duration and total cloud cover, low cloud cover and precipitation.Low cloud cover has the greatest influence on sunshine duration, followed by total cloud cover and precipitation.