The Interplay Between Topographic Gradients and Lake Effects on the Spatiotemporal Dynamics of Surface Environmental Variables in the Qinghai Lake Riparian Zone

As a critical climate regulator on the Qinghai–Xizang Plateau, Qinghai Lake exerts important influences on surrounding surface environmental conditions. Using MODIS remote sensing data and topographic information from 2000 to 2024, this study analyzed the spatiotemporal variations in land surface temperature (LST), normalized difference vegetation index (NDVI), and temperature vegetation dryness index (TVDI) in the 10-km riparian zone. The buffer was subdivided into five 2-km distance gradients to quantify the attenuation of lake effects and their interaction with topographic factors. The results indicate pronounced seasonal contrasts and distance-dependent differentiation of surface variables. LST exhibited clear seasonal variability, with peak values in the second and third quarters (Q2 and Q3). During Q2, the near-shore zone (0–2 km) remained notably cooler by approximately 2–3 °C (23.8 °C) than intermediate and distal zones (25.4–26.8 °C), indicating a moderate lake-related cooling effect during the early warm season. NDVI showed consistent seasonal phenology across all buffers, reaching maximum values in Q3, while mean NDVI values increased gradually with distance from the lake, ranging approximately from 0.48 in the near-shore zone to 0.51 in the distal zone. TVDI displayed distinct seasonal and spatial patterns, with relatively low and stable values in the near-shore zone throughout the year and a pronounced seasonal minimum in the distal zone during Q3 (0.57). These findings highlight strong seasonal and spatial heterogeneity of surface environmental conditions in the Qinghai Lake riparian zone. The observed patterns suggest that lake proximity and topographic gradients jointly influence hydrothermal conditions and vegetation dynamics at the landscape scale, providing quantitative evidence for understanding surface–environmental gradients in alpine lake systems.