Estimate Instantaneous Solar Radiation Incident upon Terrain in Bushfire Zone Using Digital Elevation Model and Natural Disaster Forecast

摘要

Effectively combined and practical methods have been applied into investigating the formation of bushfire in view of natural factors on the basis of a geographical location and local solar time under a clear weather. The instantaneous solar radiation accident onto the tilted surface of terrain in one bushfire burning zone is traced by its path. The extraterrestrial solar radiation is directly calculated by using approved astronomic formulas in which solar time and geometry are involved. Due to scattering and adsorption in atmospheric layer, extraterrestrial solar beam is classified into direct, diffuse and reflected beam when they are incident upon each tilted surface of terrain and received by it. Their calculations are performed by reliable empirical formulas respectively in a clear sky. The real values of geometric parameters of terrain are acquired by integrating digital elevation model with the corresponding satellite imagery. The solar time is determined by local time and geographical location of burning zone. Therefore, the solar radiation incident upon the complex terrain of burning zone is taking place instantaneously. The total radiant flux is sum of direct, diffuse and reflected radiant flux and located into an arbitrarily designed enclosure. It is treated to uniformly distribute and incident upon the tilted surfaces. The distribution of total radiant flux is still affected by complex terrain. Finally, by means of semi-infinite model and distribution of total radiant flux, the temperature at surface and inside soil is obtained respectively. The combined methods of research are useful in not only forecasting the risk of bushfire but also investigating soil drought.