Cross-Sensor Comparison of SWOT Level-2 Pixel Cloud and ICESat-2 ATL13 Water-Surface Elevations over Tibetan Plateau Lakes

High-altitude lakes on the Tibetan Plateau (TP) are important components of regional water-cycle regulation and climate responses, yet their long-term monitoring remains challenging due to limited in situ observations and sparse spatial sampling of conventional satellite altimetry. The Surface Water and Ocean Topography (SWOT) mission provides two-dimensional observations of inland water-surface elevation (WSE), offering new opportunities for lake monitoring in remote regions. This study evaluates the applicability of SWOT L2 Pixel Cloud (PIXC) observations for TP lake monitoring through cross-sensor comparison with ICESat-2 ATL13 observations. A total of 50 representative TP lakes were analyzed using quality-controlled SWOT–ICESat-2 matched observations. The results demonstrate that SWOT PIXC and ICESat-2 ATL13 generally capture comparable lake-scale WSE variations across the TP. The mean MAE and RMSE were 0.164 m and 0.231 m, respectively, indicating decimeter-scale cross-sensor consistency for most investigated lakes. Lake area showed no significant association with the RMSE, suggesting that lake size alone does not explain the variability of cross-sensor residuals. Further analysis reveals that residual differences are strongly scene-dependent and reflect combined influences from satellite retrieval characteristics, spatial sampling differences, environmental conditions, and temporal offsets rather than SWOT-only uncertainty. These findings provide an independent assessment of SWOT observations over high-altitude lakes and demonstrate their potential for spatially continuous monitoring of TP lake dynamics. The results also establish a foundation for integrating SWOT with multi-source satellite observations to reconstruct long-term lake water-level and storage variations.