The characteristics of sunshine duration from 1961 to 2009 in northeast China

Based on the sunshine duration,temperature,precipitation,wind speed and relative humidity data at 104weather stations from 1961 to 2009 in the northeast China,the monthly,seasonal and annual trends of the sunshine duration and its spatial distribution were analyzed using methods of a trend analysis,a Mann-Kendall test and a correlation analysis. The impacting factors of sunshine duration were also discussed. The results showthat the highest and lowest sunshine duration occurs in May and December,respectively. The annual sunshine duration has a significant decreasing tendency with 40. 5 hours per decade. The seasonal sunshine duration significantly decreases except for in autumn. The sunshine duration has an abrupt change in the early 1980s and then decreases. The sunshine duration in the northeast China is high in the west and lowin the east. Except that in the northern Heilongjiang province,the sunshine duration in the other regions is in a decreasing tendency,especially in the northern Jilin province. The annual sunshine duration is in a negative correlation with annual mean temperature,precipiation and relative humidity,and the corresponding correlation coefficients are- 0. 40,- 0. 37 and- 0. 32 respecitvely,while it is in a positive correlation with wind speed and the correlation coefficient is 0. 53. The relative humidity coefficient passes 99. 5% confidence levels,and the other passes 99. 9% confidence levels.