Spectra method for revealing relations between slope and possible sunshine duration in China

摘要

Possible sunshine duration (PSD) determines the solar energy received by the surface of Earth. The objective of this research is to explore the spatial structure of PSD which is closely related to slope and PSD. We chose 40 sample areas representing diversified landforms in China and then computed the PSD by using the digital elevation models (DEMs) with a resolution of 30 m for the sample areas. We define the concept of the spectrum which reveals the relation between the PSD and slope over an analysis window on the DEM, and propose the method for deriving the spectrum. Using this method, we derive the corresponding spectra in a year or in a season in the study areas when the analysis window is larger than the corresponding value of area, the stable area. The value of the spectrum generally decreases with the slope; the stable area is positively related to the variation in the slope and that of the relief degree. The spectrum may be useful for computing PSD while considering the shielding effect quickly; the stable area may be used as the minimum value of the area in studies on the spatial structure of PSD; this method might be a quantitative one in geography for revealing the spatial structure of other meteorological factors.