Measurement report: Can Zenith Wet Delay from GNSS "see" atmospheric turbulence? Insights from case studies across diverse climate zones

Abstract. Global Navigation Satellite Systems (GNSS) microwave signals are almost unaffected by clouds but are delayed as they travel the troposphere. The hydrostatic delay accounts for approximately 90 % of the total delay and can be well modeled as a function of temperature, pressure, and humidity. On the other hand, the wet delay is highly variable with space and time, making it difficult to model accurately. A zenith wet delay (ZWD) can be estimated as part of the GNSS positioning adjustment and is proportional to the specific humidity in the atmospheric boundary layer (ABL). Whereas its average term can describe mesoscale events, its small-scale component is associated with turbulent processes in the ABL and the focus of the present contribution. We introduce a new filtering and estimation strategy to analyze small-scale ZWD variations, addressing questions on daily or periodic variations of some turbulent parameters, and the dependence of these parameters on climate zones. Five GNSS stations were selected for case studies, revealing promising specific daily and seasonal patterns depending on the estimated turbulence at the GNSS station (buoyancy or shear). This research lays the groundwork for more accurate models and prediction strategies for integrated WV turbulence. It has far-reaching applications, from nowcasting uncertainty assessments to the stochastic modeling for Very Large Baseline Interferometry or GNSS.