Analyzing Different Parameterization Methods in GNSS Tomography Using the COST Benchmark Dataset

Abstract

GNSS tomography is an emerging remote sensing technique in the field of meteorology that is gaining increased attention in recent years. This method is used as a tool for atmospheric (particularly tropospheric) sensing and then applied in nowcasting and forecasting research. The tomographic approach can be used to determine the distribution of water vapor (WV), the most active component of the atmosphere. WV is one of the most important drivers of convection and precipitation. In this method, numerous line-of-sight integral observations at different locations and directions are used to derive a 3-D distribution of a WV structure. One of the challenges in GNSS tomography is that different parameterization methods are used for computing the design matrix. Here, the effect of the straight-line method versus the ray-tracing method is investigated for computing the length of a ray which passes through the model element. In addition, the effect of considering the topography of the area in the tomography model is analyzed. The accuracy of the developed model is verified using radiosonde measurements in the COST benchmark dataset. Results show that the Eikonal ray-tracing method is superior to other schemes whether used with topography or not. The mean values of RMSE of estimated wet refractivity with respect to the radiosonde profiles for these schemes are about 1.313 and 1.766 ppm, respectively. This work is conducted within COST Action ES1206 on “Advanced global navigation satellite systems tropospheric products for monitoring severe weather events and climate (GNSS4SWEC) (2013–2017)” and IAG Working Group “GNSS tomography.”