Evaluation of High Resolution ICESat-2 ATL03 Photon Data for River Level Estimates in Mountainous Areas

Abstract:

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. 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 missions provides exceptional opportunities for inland water studies. Using the ATL03 product, the Yangtze River is mapped in great detail, and the data even reveals objects in the river channel.

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 the upstream parts of the Yangtze and Yellow Rivers, where even SAR missions such as CryoSat-2 and Sentinel-3 have been unsuccessful. Results are also shown for the upstream part of the Nu River in China, which is very narrow and surrounded by steep mountains south-east of the Tibetan Plateau.