Study On Application Of Modelling Direct Solar Radiation On GIS In Jieba Mountain

The research on space-time distribution regularies of solar direct radiation were conducted, which were based on the solar radiation model of ViewGIS and associated with the key project supported by Department of Education "the method research on quantitative land evaluation near altiplano bashang" (104032). The purpose of this paper is to provide primal data and scientific evidence for region plan and environment construction.At the beginning of this paper, method and principium of solar radiation simulation by ViewGIS were introduced. Then the error analysis and accuracy alignment of this simulation model were conducted which were based on continuous positioning observation data of solar radiation in 2004. Result of error analysis showed that the average simulation error was about 3.17% almost in all the sunny days except a small number of moments with the error more than 10%. So the accuracy can meet the need of research. On the other hand, in few-cloudy and cloudy days, the error was 15.50% and 41.28% respectively which showed that error increases with cloudage. So the model doesn't go well in few-cloudy and cloudy days.A new attribute database was established by appending simulating solar radiation data from ViewGIS to original attribute database. With the foundation of this new database, the total solar radiation amount of one day, one month and one year were calculated respectively of 24 solar terms in 1977, the representative year. The result of spatiotemporal distribution showed that during one day, the value of solar radiation is low in morning and evening but high at noon(11:30-13:30), with the variation range of 906.71 -916.68J/m~2·s. In 24 solar terms, the max and min of solar radiation appear respectively in the Summer Solstice and the Winter Solstice with the value of 25.16MJ/m~2 and 3.99MJ/m~2, which follow the regularity of normal distribution with the centre of the Summer Solstice. During a year, solar radiation variation regularity is single peak curve and the max and min of value was 752.53 MJ/m~2 and 128.79 MJ/m~2 which appears respectively in July and December.By analyzing spatial distribution, the regularity was found that geomorphology affects direct radiation significantly. Direct radiation increases with elevation and there are the most amounts at plantation and the fewest at lower part of hill. The regularity is plantation>flood land>summit>middle and upper part of hill>gully>lower part of hill. On the other hand, direct radiation decreases with the increase of slope and the breakpoints are the value of range between 3° and 8° was 29.87 MJ/m~2 higher than that of 8° -15° ,and the value of range between 15° -35° was 27.81 MJ/m~2 higher than that of ≥ 35° .The direct radiation also varies with slope aspect and the regularity is sunny slope>semi-sunny slope > semi-shady slope > shady slope.