Effect of Spatial Scale of DEM on Spatial Simulation of Duration of Possible Sunshine: A Case Study in Xianju County, Zhejiang Province

doi:10.3969/j.issn.1000-6362.2019.04.006

Abstract

Abstract:

To analyze the effects of DEM with different spatial resolution on the numerical simulation of Duration of Possible Sunshine (DPS) based on DEM, Xianju County in Zhejiang Province was selected as the study area. DEM data with four spatial resolutions (10m, 30m, 90m, and 900m) derived from 1:10000 digital topographic map, ASTER GDEM, SRTM and GTOPO30′, respectively were used in this study. The topographic factors of altitude, slope, aspect, etc were derived from DEM. Using digital terrain analysis and spatial analysis for topographic factors and the distributed statistical model of DPS in GIS platform, this paper simulated the spatial distribution of DPS with four spatial resolutions in January and July. Then the effect of DEM scale on DPS simulation was analyzed. The results showed that spatial heterogeneity of DPS decreased as the spatial resolution decreased. Spatial distribution characteristics of DPS with topographic factors became increasingly hard to identify. The spatial data statistics showed that the average value increased with decreasing spatial resolution, while the standard deviation decreased. The maximum value varied little with spatial resolution, but the minimum value was quite different. Affected by altitude and other topographical factors, DPS was longest on flat and mountain ridges, while it was shortest in the region distributed at altitudes from 200?400m above sea-level. Moreover, it increased with the increasing altitude from 400-1100m above sea-level. Taking the DPS with 10m resolution as reference, the difference between the DPS with the other three spatial resolutions and the DPS with 10m resolution increased with the decrease of resolution. The minimum was at an altitude of <100m. The greatest differences were concentrated in the region of 700-900m. The average daily DPS in January were about 0.7h, 1.4h, and 2.9h more, while the one in July were about 0.5h, 0.9h, and 2.3h more. The DPS decreased with the increase of slope when the slope was in the range of 0-55°. The difference between the DPS with three spatial resolutions (30m, 90m, and 900m) and the reference value with 10m resolution increased with the decrease of resolution. The minimum all appeared in the flat region of slope 0-5°. The maximum occurred in the area with a steeper slope. The average daily DPS in January were about 2.1h, 1.8h, and 1.7h more, while the one in July were about 0.3h, 0.6h, and 1.2h more. Due to the effect of sloar altitude and azimuth angle, there was a great DPS differences between the south slope and the north slope. While the differences between SE slope and SW slope, E slope and W slope, NE slope and NW slope were smaller. The DPS differences with the reference value in all slopes increased with the decrease of resolution. In the northern slope (N, NE, and NW slopes), the difference in January was greater than that in July. The maximum occurred in the northern (N slope) slope of January. The average daily DPS were about 1.4h, 2.5h, and 4.8h more. In the southern slope (S, SE, and SW slopes), the difference in January was less than that in July. The maximum occurred in the southern slope (S or SW slope) of July. The average daily DPS were about 0.5h, 0.9h, and 2.1h more.

Key words: Mountain area, Duration of possible sunshine, Digital elevation model, Scale effect, Spatial distribution

LI Jun，WANG Chao，ZHAO Yu-zhu. Effect of Spatial Scale of DEM on Spatial Simulation of Duration of Possible Sunshine: A Case Study in Xianju County, Zhejiang Province[J]. Chinese Journal of Agrometeorology, 2019, 40(04): 250-259.

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