Distributed modeling of extraterrestrial solar radiation over the rugged terrains of Pakistan

In Pakistan, the solar analogue has been addressed but its surface geographical parameterization has given least attention. Inappropriate density of stations and their spatial coverage particularly in difficult peripheral national territories, little or no solar radiation data, nonsatisfactory sunshine hours data, and low quality of ground observed cloud cover data create a situation in which the spatial modeling of Extraterrestrial Solar Radiation(ESR) and its ground parameterization got sufficient scope. The Digital Elevation Model (DEM) input into Geographic Information System (GIS) is a compatible tool to demonstrate the spatial distribution of ESR over the rugged terrains of the study domain. For the first time, distributed modeling of ESR is done over the rugged terrains of Pakistan, based on DEM and ArcGIS.. Results clearly depict that the complex landforms profoundly disrupt the zonal distribution of ESR in Pakistan. The screening impact of topography is higher on spatial distribution of ESR in winter and considerably low in summer. The combined effect of topography and latitude is obvious. Hence, the model was further testified by plotting Rb (ratio of ESR quantity over rugged terrain against plane surface) against azimuth at different latitudes with different angled slopes. The results clearly support the strong screening effect of rugged terrain through out the country especially in Himalayas, Karakoram and Hindukush (HKH), western border mountains and Balochistan Plateau. This model can be instrumental as baseline geospatial information for scientific investigations in Pakistan, where substantial fraction of national population is living in mountainous regions.