ICESat-2 Lidar Estimates of Clear-Sky Precipitation Over the East Antarctic Plateau

Precipitation over Antarctica plays a critical role in determining the mass balance of the ice sheet, yet it remains poorly quantified due to the harsh environment and sparse number of observations. Over the East Antarctic Plateau, clear-sky precipitation (CSP) is a significant portion of the total annual precipitation. CSP consists of very small ice crystals that form when the air becomes supersaturated and settles to the surface. This study presents the first continental-scale estimates of CSP over the East Antarctic Plateau using atmospheric backscatter profiles from the Ice, Cloud and land Elevation Satellite-2 (ICESat-2) lidar. A method is developed to identify CSP based on calibrated attenuated backscatter and to estimate the associated precipitation amounts by deriving ice water content from lidar extinction and using an estimated particle fall speed to obtain precipitation rate. Comparisons with in situ measurements at Concordia Station, Dome C show general agreement. Results for the April–October 2021 period reveal a high frequency of CSP (up to 80%) across the high Plateau. The ICESat-2 estimated CSP amount for this period ranges from about 5 to 8 mm snow water equivalent (SWE) south of about 80S and increases toward the north with maximum values of 18–20 mm SWE near 70S, 90E. The ICEsat-2 estimated CSP amount for the grid box containing Dome C was 8.5 mm SWE which agrees well with the amount measured there (9.9 mm SWE). These findings demonstrate the unique ability of ICESat-2 to detect and quantify CSP, offering new insight into Antarctic precipitation and providing a valuable data set for evaluating the surface mass balance of Antarctica.