Evaluation of snow depth retrievals from ICESat-2 using airborne laser-scanning data

The unprecedented precision of satellite laser altimetry data from the NASA ICESat-2 mission and the increasing availability of high-resolution elevation datasets open new opportunities to measure snow depth in mountains, a critical variable for ecosystem and water resource monitoring. We retrieved snow depth over the upper Tuolumne basin (California, USA) for 3 years by differencing ICESat-2 ATL06 snow-on elevations and various snow-off digital elevation models. Snow depth derived from ATL06 data only (snow-on and snow-off) offers a poor temporal and spatial coverage, limiting its potential utility. However, using a digital terrain model from airborne lidar surveys as the snow-off elevation source yielded a snow depth accuracy of similar to 0.2 m (bias) and precision of similar to 1 m (random error) across the basin, with an improved precision of 0.5 m for low slopes (< 10 degrees), compared to eight reference airborne lidar snow depth maps. Snow depths derived from ICESat-2 ATL06 and a satellite photogrammetry digital elevation model have a larger bias and reduced precision, partly induced by increased errors in forested areas. These various combinations of repeated ICESat-2 snow surface elevation measurements with satellite or airborne products will enable tailored approaches to map snow depth and estimate water resource availability in mountainous areas with limited snow depth observations.

Automated summary

The precision of satellite laser altimetry data and the availability of high-resolution elevation datasets provide new opportunities to measure snow depth in mountains. By comparing different digital elevation models, snow depth in the upper Tuolumne basin in California was retrieved for 3 years. Using a digital terrain model from airborne lidar surveys as the snow-off elevation source yielded a snow depth accuracy of about 0.2 m (bias) and precision of about 1 m (random error) across the basin, with improved precision of 0.5 m for low slopes (< 10 degrees).