GiRsnow: an open-source software for snow depth retrievals using GNSS interferometric reflectometry

Snow is an important water resource that plays a critical role in the global climate and hydrological cycle. Thus, Global Navigation Satellite System Interferometric Reflectometry (GNSS-IR) has emerged as a new remote sensing technology for monitoring snow depth. We developed the snow parameter processing software GiRsnow, based on GNSS-IR tools and a MATLAB environment, to obtain robust and effective retrievals. That tool allows users to check the data quality, draw reflection point trajectory and Fresnel zone, retrieve snow depth using signal-to-noise ratio (SNR) observations or geometry-free linear carrier phase combination (termed L4) observations, and display the results based on the time and space domain. We conducted two experiments at the Plate Boundary Observation site RN86 and GPS Earth Observation Network (GEONET) site 020877 to validate the performance of the software. Our results demonstrate that GiRsnow can process multi-constellation and multi-frequency GNSS data and obtain robust and effective results through quality control and a grid model to account for topography effects.