TITLE:
Modeling of Diffuse Solar Radiation and Impact of Complex Terrain over Pakistan Using RS/GIS
AUTHORS:
Shahzad Sultan, Renguang Wu, Iftikhar Ahmad, M. Fahim Ahmad
KEYWORDS:
Rugged Terrain, Diffuse Radiation, Pakistan, GIS, DEM
JOURNAL NAME:
Journal of Geographic Information System,
Vol.6 No.4,
August
25,
2014
ABSTRACT: Diffuse solar radiation is
subject to the combined influence of ground and sky factors, such as
topography, geography of the area and cloud cover. This study attempts to
quantify the impacts of topography, sky factors and the cloud cover on the
distribution of diffuse solar radiation over Pakistan. Distributed modeling
approach by considering anisotropy scattering mechanism was adopted. Digital
elevation model and observed data are used to derive average monthly diffuse
solar radiation values over the rugged terrains of Pakistan. Extraterrestrial
solar radiation model, sky view factor model (openness model) and digital
elevation model (DEM) are applied to investigate the impacts of ground factors,
while diffuse solar radiation model for horizontal surface was considered for
sky factors. Furthermore, corrected MODIS cloud fraction data are incorporated
using GIS plat form. Results show that the highest amount of diffused solar
radiation occurs during the monsoon months along the eastern side of the River
Indus, when the sky is covered by clouds of various heights and densities. The
variation due to topography is evident in mountainous areas, particularly in
the North Pakistan and over the Baluchistan Plateau.