Abstract:With the development of automation of meteorological data, pyrheliometer which can automatically track solar position to observe sunshine duration has been gradually used in meteorological operations. It is necessary to quantitatively evaluate the difference between pyrheliometer and sunshine recorder observations. This paper discusses the differences between pyrheliometer and sunshine recorder observations over different regions, seasons and time scales. The results are as follows: (1) The sunshine duration observed by pyrheliometer is 0.51 h·d-1 (8.30%) less than that by sunshine recorder. The difference has obvious seasonal and regional variations, which are larger in summer and spring, but the minimum in winter, and also larger in Northwest and Hainan, but the least in Northeast, Huang Huai and Sichuan Basin. (2) Pyrheliometer observation is about 0-0.3 h·h-1 less than sunshine recorder observation at sunrise, and 0-0.3 h·h-1 larger than sunshine recorder observation at sunset while the difference is between ±0.2 h·h-1 in other hours. (3) Affected by observing instruments and weather conditions, the difference between two kinds of sunshine durations are -0.17 h·d-1 (-1.88%) under clear sky conditions, -0.64 h·d-1 (-9.08%) under cloudy conditions, and -0.62 h·d-1 (-26.73%) under overcast conditions. (4) The correlation coefficient between the two kinds of sunshine durations is above 0.88.