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.
Highlights
Pakistan is the 33rd largest country (803,940 km2) with more than twice the size of Japan featuring heterogeneous terrain from 0 m altitude in coastal belts to 8000 m in Himalaya ranges [1]
Diffuse Solar Radiation Distributed over the Irregular Topography By putting the values in Equation (1), we have the spatial distribution pattern of diffuse solar radiation over the rugged topography
There is an uneven variation in mountains of Gilgit Baltistan and Kashmir regions in northern Pakistan due to varying slopes in term of direction and height, i.e. aspect ratios and complex topographic effects on weather
Summary
Pakistan is the 33rd largest country (803,940 km2) with more than twice the size of Japan featuring heterogeneous terrain from 0 m altitude in coastal belts to 8000 m in Himalaya ranges [1]. The whole country has only 5 meteorological stations measuring solar radiation and none of them have diffuse solar radiation measurements. It is, imperative to find other ways to estimate the solar radiation over such complex terrain. The scattered radiation is called diffuse radiation. Diffuse cloud radiation appears to only contribute a minor part to radiation energy from above the mid-visible to the infrared spectrum, but can contribute up to 40% of the radiation energy from the mid-visible through mid-ultraviolet spectrum [2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
