Regional and Altitude-Dependent Estimate of the SRTM C/X-Band Radar Penetration Difference on High Mountain Asia Glaciers

Radar penetration correction is essential for accurately estimating glacier mass balance when using the geodetic methods based on the radar-derived digital elevation model (DEM). Due to heterogeneous snow distribution and snowpack properties, the radar penetration depth varies by region and is basically dependent on the altitudes. However, a constant value is usually used to correct the radar penetration for regional glacier mass balance estimation in high-mountain Asia (HMA), because little is known about the detailed distribution of radar penetration depth of the glacierized area in HMA. In this study, the penetration depth difference (hereafter referred to as PDD) of the C/X-band radar signals on glaciers over the whole HMA region was first estimated by comparing the Space Shuttle Radar Topographic Mission (SRTM) C/X-band digital elevation models (DEMs), and the spatial characteristics of the altitude-dependent PDD were analyzed on a 1° × 1° grid. The C/X-band radar PDD (the X minus C band penetration) was calculated in each 50-m elevation bin, and a linear model was used to study the correlation between the altitude and the penetration difference. The results show that the difference of the SRTM C/X-band penetration depth in the HMA region is between −1.67 0.65 m and 7.63 0.99 m, with an average value of 2.40±0.04 m. A significant linear positive correlation between elevation and the PDD was found in most of 1° × 1° grid regions in HMA. These results can be used as important reference data for estimating glacier mass balance in HMA based on SRTM DEMs.