Model Construction Among Light, Thermal, Water Factors And The Preliminary Applications Based On ViewGIS

Research on spatial distribution regularies of solar radiation and hydro-thermal factors and the method of land suitability 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.Based on the data observed during growing season in 2004 and 2005 and with the mathematic methods such as combination of math and figure, curve fitting, nonlinear fitting and harmonic analysis, the regulation of dynamic variation and topography-affected were researched. The results showed variation of direct solar radiation, diffuse solar radiation and land defected solar radiation were all quadratic forms which were fitted on significant level. The condition of cloud and air were the most important factors affecting direct solar radiation and diffuse solar radiation, while was not so influential to defected solar radiation. The factor which affected defected solar radiation significantly was topography.Heat factors which included air and soil temperature(5cm,10cm and 20cm) varied following the cosine curve. Topography was also significant to hydro-thermal factors. The distribution regularity of air temperature is sunny slope >summit plane > shady slope as well as ground temperature (5cm,10cm,20cm). The air humidity was in the order of shady slope>summit plane>sunny slope and the soil moisture was in the order of summit plane > shady slope > sunny slope. Air humidity at different topography had great diversity and the variations during one day were sine forms. Soil moisture at different deepness duringone day varied little and the value about 10 o'clock was approximate to the average value of one day. The variation of soil moisture during one day could be described significantly by power function. Models of solar radiation and hydro-thermal factors were achieved with some mathematic methods including correlation analysis, regression analysis, curve fitting and PCA, which accomplished to factors quantification. The primal main results included that no matter at summit, sunny or shady slope the variation of direct solar radiation and air temperature is quadratic form ,the variation of air and soil temperature is positive linear and the variation of air temperature and humidity was negative linear. The correlation between 5cm-depth soil temperature and soil moisture could be described by exponent function, while 10cm-depth and 20cm-depth soil temperature and soil moisture were not too correlative.Then, the spatial distribution regular of solar radiation and hydro-thermal was researched on the scale of whole region. The results showed that in Xiaobazi country, solar resource was plentiful and solar radiation in 70% of the total area was 2000-2500J/m~2 d. In this research, the relative low value of solar radiation collection zone in Xiaobazi country was discovered and named. During growing season, air temperature was in range of 10-15 ℃ and the air temperature in south-eastern zone was higher than that of middle and western zone. Soil temperature of 5cm-depth was ≥10℃ at large, 20cm-depth soil temperature was ≥15℃ and 20cm-depth soil temperature centered around range of 5-10℃. One relative high value of soil temperature collection zone in Xiaobazi country was discovered and named. Air humidity condition in Xiaobazi country was fine, especially on slope conditions. While the soil moisture condition was bad and in 60% of the total area soil moisture was ≤ 10%.In this research, the land suitability evaluation was conducted with the method principle components and indices sum. The results showed that in Xiaobazi County, area suitable for forestry was 223.46 km~2 which was 73.26% of the total area. The condition suitable for forestry on slope was better than summit and that on shady slope was better than that on sunny slope. Overall, the foreground of forestry development in Xiaobazi country was extensive.