The ICESat-2 Inland Water Height Data Product: Evaluation of Water Profiles Using High Altitude Photon Counting Lidar

Abstract:

The Advanced Topographic Laser Altimeter System (ATLAS) on the Ice, Cloud, and Land Elevation Satellite (ICESat-2), scheduled to launch in 2017, is a low energy, high repetition rate, short pulse width, 532 nm lidar. Although primarily designed for icecap and sea ice monitoring, ATLAS also will record dense observations over Pan-Arctic inland water bodies throughout its designed three year life span. These measurements will offer improved understanding of the linkages between climate variability and Arctic hydrology including closure of the Pan-Arctic water balance. An ICESat-2 Inland Water Body Height Data Product is being developed consisting of along-track water surface height, slope, and roughness for each ATLAS strong beam, and also aspect and slope between adjacent beams. The data product will be computed for all global inland water bodies that are traversed by ICESat-2 during clear to moderately clear atmospheric conditions. While the domain of the ATL13 data product is global, the focus is on high-latitude terrestrial regions where the convergence of the ICESat-2 orbits will provide spatially dense observations. Water bodies will be identified primarily through the use of an “Inland Water Body Shape Mask”. In preparation for the mission, the Multiple Beam Altimeter Lidar Experimental Lidar (MABEL), was built and flown during numerous high altitude experiments, observing a wide range of water targets. The current analysis examines several MABEL inland and near coastal coastal targets during 2012 to 2015, focusing on along track surface water height, light penetration into water under a range of atmospheric and water conditions. Sites include several Alaska lakes, the Chesapeake Bay, and the near shore Atlantic coast. Results indicate very good capability for retrieving along track surface water height and standard deviation and penetration depth. Overall, the MABEL data and subsequent analyses have demonstrated the feasibility of the ATL13 algorithm for providing quantifiable ICESat-a data products of inland and near shore waters.