TY  - JOUR
AU  - Zhang, Huake
AU  - Kou, Xiaokang
AU  - Xu, Huan
AU  - Yi, Shuang
AU  - Sun, Wenke
AU  - Wang, Qiuyu
PY  - 2025
TI  - Assessing CryoSat-2 Satellite's seasonal accuracy in lake water level monitoring
JO  - Geodesy and Geodynamics
SN  - 1674-9847
SP  - 172
EP  - 182
VL  - 16
IS  - 2
AB  - Changes in lake levels, as an indicator of climate change, are crucial for understanding water resources. Satellite altimetry has proven to be an effective technique for monitoring water level changes in inland lakes. However, high-altitude and high-latitude lakes undergo seasonal freezing and melting, affecting satellite altimetry accuracy. This paper evaluates the accuracy of lake level height observations by the CryoSat-2, which uses synthetic aperture radar (SAR) across seasons. First, we used lake boundary based on optical remote sensing data to extract the footprints of CryoSat-2 that fall on Namco and Zhari Namco. After elevation conversion and anomaly identification, we obtained the time series of lake levels. These data were compared and verified against lake levels from in-situ measurements to assess the accuracy of CryoSat-2. The results show that CryoSat-2 can monitor lake level height with an accuracy of about 10–13 cm. The correlation coefficient between CryoSat-2 observations and in-situ measurements over Namco is 0.80 (p < 0.01), with a Root Mean Square Error (RMSE) of 13 cm. For Zhari Namco, the correlation coefficient is 0.91, with an RMSE of 10 cm, indicating a better match. At the seasonal scale, the seasonal correlation coefficients between CryoSat-2 and in-situ measurement in Namco are 0.47 (spring), 0.79 (summer), and 0.91 (fall) with no observations available for winter. The lower correlation in spring may be due to incomplete ice melting. For Zhari Namco, the seasonal correlation coefficients are 0.89 (spring), 0.93 (summer), 0.89 (fall), and 0.87 (winter). The results show that CryoSat-2 accuracy is higher in summer and fall, while slightly lower in spring and winter, indicating that ice formation affects accuracy. Even during winter, the altimetry results do not significantly exceed the in-situ lake water level observations.
UR  - https://doi.org/10.1016/j.geog.2024.12.003
DO  - 10.1016/j.geog.2024.12.003