The Spatial and Temporal Distribution of Insolation Duration over Rugged Terrains in the Guizhou Plateau

Due to local terrain factors such as slope, aspect and terrain inter-shielding, the insolation duration over rugged terrain is different from over horizontal surface. Calculating the insolation duration over rugged terrain is very difficult. In the mountainous regions of complicated landform and great height difference, the observation data of the existing weather stations are far from enough to reflect the spatial distribution of the complicated sunshine time.Guizhou Province, which is from 24°37′N to 29°13′N and from 103°36′E to 109°35′E, lies in the plateaus and mountains in the western China. The physiognomy of the whole Province falls roughly into the categories of plateaus, mountains, hilly land, and basins. 92.5% of the total land area is mountains and hilly land. Based on Digital Elevation Model (DEM) and Geographical Information System (GIS), the distributed models for calculating insolation duration over rugged terrain are developed. Applying the models to Guizhou Plateau with 100 m×100 m DEM data, the elaborated spatial distributions of insolation duration over rugged terrain are generated. The insolation duration over rugged terrain of considering slope, aspect and terrain inter-shielding is analyzed.The influences of slope, aspect and the terrain inter-shielding on sunshine duration are very big. The spatial distribution of sunshine duration has apparent terrain feature over rugged terrain. The solar altitude angle is quite low in January; the effect of slope, aspect is very apparent. The shadow areas of topography are relative large and the spatial difference of sunshine time is big. The insolation duration varies spatially from 16 to 142 hours, and the maximum is about 9 times as the minimum. The solar altitude angle is quite high in July; the shadow areas of topography are relative small. The insolation duration varies spatially from 133 to 210 hours, and the maximum is about 1.6 times as the minimum. But the sunshine time over horizontal surface is much in July, and the influence of local terrain on the insolation duration is still obvious. The insolation duration and its amplitude of variation vary between in January, July and in April, October. The annual average insolation duration varies spatially from 768 to 1824 hours, and the maximum one is about 2.4 times as the minimum one. The effect of slope, aspect and the terrain inter-shielding on annual sunshine duration is quite great. The spatial difference of it is very evident. Therefore, the effect of complex topography on insolation duration should be considered.