Quantifying Direct Solar Radiation and Topographic Effect of Driving Factors over Rugged Terrain in Lhasa City: Implications for Regional Sustainable Solar Energy Utilization

Rugged terrain dominates the Qinghai–Tibet Plateau, where complex landforms profoundly modulate solar energy availability. The reasonable distribution and development of solar energy resources in this region should be based on the accurate assessment of the effects of complex topography. This study proposes a high-resolution methodological framework to quantify the topographic–climatic interactions within Lhasa. Based on GIS technology (ArcGIS 10.8), this study employs a topographic decomposition method to extract micro-topographic variables, which are integrated into a distributed solar radiation model with 30 m resolution to simulate spatial–temporal radiation dynamics. Furthermore, we utilize the geographical detector (GD) model to attribute the spatial variance of radiation to specific topographic and surface drivers. The results show that: (1) The seasonal distribution of solar radiation is highly heterogeneous, with the monthly average extraterrestrial solar radiation (ESR) peaking in July (1190 –MJ/m2) and reaching its lowest in December (469 MJ/m2). (2) Factor detection using the GD model indicates that slope aspect (q = 0.49) and Sky View Factor (SVF, q = 0.38) are the primary individual drivers of direct solar radiation, followed by surface albedo (q = 0.26) and DEM (q = 0.12). (3) Interaction detection reveals strong non-linear synergies, where the combined interaction of aspect and SVF yields the highest explanatory power (q = 0.889), followed by slope and albedo (q = 0.732). The outcomes of this research provide both a theoretical foundation and high-resolution spatial datasets to support photovoltaic site selection, enhance passive solar building design, and advance refined sustainable energy planning in complex alpine terrains globally.