Spatial and Temporal Distribution Characteristic of Sunshine Duration in Dali Mountains

doi:10.3969/j.issn.1673-7148.2011.03.012

Abstract：This article simulated calculates the spatial and temporal distribution of mountains＇ sunshine duration in Dali based on the digital elevation model（DEM）.The results show besides the percentage of sunshine,slope,aspect and the masking of terrain have a great effect on the distribution of sunshine duration.The solar altitude is smaller in winter,the masking of terrain has a great impact on sunshine duration,but it＇s smaller relatively in summer.The ratio of masking in April is maximum and in December is minimum all year around.Any time of year with the increase in slope the sunshine duration is reduced.The aspect has a strong seasonal on the sunshine duration： the northern slope and southern slope are equal to a maximum duration of sunshine in vernal equinox and autumnal equinox,the northern slope is maximum in summer solstice and the southern slope is maximum in winter solstice.During the vernal equinox to the autumnal equinox,sunshine duration in the northern slope is maximum,the southern slope is maximum in the rest of time,but the annual sunshine duration is maximum in the southern slope.The ratio of masking terrain in 105 ° and 255 ° of slope is 0.82 all year round,and the ratio is not variable with time.