Evaluation of ICESat-2 ATL03 and ATL13 River Levels in Mountainous Areas of China

The data from NASA’s Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) mission offer a unique opportunity to map rivers and lakes with an unprecedented number of observations in areas where previous missions have failed to provide valuable water level estimates. ICESat-2 carries just one instrument, the Advanced Topographic Laser Altimeter System (ATLAS), which is a green wavelength, photon-counting lidar, and several data products are available, such as the ATL03 product, which holds the photon data, and the ATL13 product which contains estimated inland water surface heights and statistics for water bodies across the world. The along-track resolution of the ATL03 product is less than 1 m, and with the three pairs of beams, i.e. six beams in total, the mission provides exceptional opportunities for inland water studies in areas with mountainous topography.

In general, inland water altimetry in mountainous areas has proven to be a challenge for both conventional Low Resolution Mode (LRM) and Synthetic Aperture Radar (SAR) altimetry, causing issues not only with waveforms, but also the position of the range window. In this study, we present the ability of ICESat-2 to obtain water levels in several mountainous rivers in China, where even SAR missions such as CryoSat-2 and Sentinel-3 have been unsuccessful. Results are shown for both the ATL03 and the ATL13 version 4 products to evaluate their performances.