Evaluation of spatial-temporal changes in incoming shortwave radiation in western Iran

Shortwave radiation (SWR) as one of the fundamental components of the Earth’s climate system plays a key role in regulating the surface energy balance, controlling ecological processes, and shaping patterns of human activities. The present study aims to investigate the spatiotemporal variability of shortwave radiation in western Iran over the 2000–2022 period using satellite data and products, focusing on spatial and seasonal patterns across the provinces of Kurdistan, Kermanshah, Ilam, Hamedan, and Lorestan. In this research, MODIS sensor data were used to estimate net surface incoming radiation, and regional-scale spatiotemporal analyses were performed. The results indicate that western Iran has a high potential for solar energy reception, with an estimated annual mean radiation of approximately 1800 to 2200 kWh per square meter and more than 280 sunny days per year. Spatially, the highest radiation values were observed in the elevated and low-cloud regions of northwestern areas, while lower values were recorded in southern and southwestern regions due to higher humidity and cloud cover. Temporally, the seasonal pattern shows maximum radiation in summer and minimum in winter. This pattern is primarily driven by variations in solar zenith angle, day length, cloud conditions, humidity, and topographic characteristics. Overall, the findings suggest that western Iran, particularly the Zagros highlands, has considerable potential for solar energy development, and the results can support strategic planning for renewable energy expansion and sustainable resource management.