Validation of ICESat-2 Derived Data Products on Freshwater Lakes: Bathymetry, Diffuse Attenuation Coefficient for Downwelling Irradiance (K_d), and Particulate Backscatter Coefficient (b_bp)

Monitoring large bodies of water, such as the Laurentian Great Lakes in North America, can be challenging and costly. The bathymetry, the diffuse attenuation coefficient for downwelling irradiance ( $K_{d}$ ), and the particulate backscattering coefficient ( $b_{\text {bp}}$ ) are important metrics in monitoring water quality in lakes and have typically been measured in two ways: 1) via in situ sampling campaigns, which are expensive, time-consuming, and have a low spatial resolution; and 2) via passive optical imagery, which can have errors in excess of 50%. Recently, Ice, Cloud, and land Elevation Satellite-2 (ICESAT-2), an active light detection and ranging (LiDAR)-based satellite, has proven effective in deriving the bathymetry, $K_{d}$ , and $b_{\text {bp}}$ in the global oceans. However, validation of such metrics has never been done on satellite flyovers taken on the same day as in situ measurements. Likewise, studies on freshwater environments have been limited. Here, we compare in situ data sampled from Lake Michigan and Big Glen Lake between August 13th and 14th, 2021, and results derived from an ICESat-2 flyover in the same region on August 14th, 2021. We find excellent agreement between the in situ values and the satellite-derived values for all three metrics. This suggests that ICESat-2 and other future LiDAR-based satellites will be powerful tools for monitoring large freshwater lakes.