M.V. Meshcherova1, O.G. Khutorova2, V.E. Khutorov3

1–3 Kazan (Volga Region) Federal University (Kazan, Russia)

1maryamaslova1861@mail.ru, 2Olga.Khutorova@kpfu.ru, 3pri870@yandex.ru

The use of atmospheric models to correct global navigation satellite system (GNSS) signals is driven by the need to improve the accuracy of positioning and other radio measurements during atmospheric radio propagation. Tropospheric delay is one of the main sources of error in GNSS measurements. Modeling data allows for more accurate prediction of zenith tropospheric delay, which is critical for high-precision positioning, including precision point positioning (PPP) and real-time positioning (RTK) methods. Comparison of zenith tropospheric delay from GNSS data and ERA5 reanalysis allows for the identification and correction of systematic measurement discrepancies. The aim of this study is to assess the accuracy of zenith tropospheric delay re-production in the ERA5 reanalysis model by comparing it with independent GNSS measurements, determine the magnitude of systematic errors, and validate the feasibility of using ERA5 for signal correction using the example of the Republic of Tatarstan. This paper uses zenith tropospheric delay and integrated moisture content series calculated from second-by-second GNSS observations from a high-precision positioning receiver in Kazan for 2009–2022. The ZTD and IWV parameters were estimated with a 5-minute step. The ERA5 reanalysis data obtained using the ECMWF model contain fields of integrated atmospheric moisture content. The zenith tropospheric delay was calculated using air pressure, humidity, and temperature data at specific altitudes or isobaric surfaces. The initial temporal resolution of the reanalysis was 1 hour. To account for the contribution of mesoscale processes to the GNSS series residuals relative to the reanalysis, instantaneous experimental data corresponding to the ERA5 time samples were used for comparison. Since the original spatial resolution of ERA5 is 0.25 degrees, two-dimensional nonlinear interpolation was used to obtain these parameters at the GNSS receiver coordinates. The average discrepancies between global navigation satellite system data and the ERA5 reanalysis and their standard deviations for each season were obtained. The results show that the minimum standard deviations and maximum standard deviations are observed in summer. These results are explained by increased fluctuations due to increased humidity during the warm season. It is clear that the resolution of GNSS monitoring describes the ZTD dynamics with higher resolution. Depending on the year, the maximum discrepancies between ZTD observations from GNSS and ERA5 data for Kazan range from 51 to 109 mm. Estimates of the relative discrepancies for the entire observed period do not exceed 2-4% of the ZTD value. The correlation coefficient of ZTD for GNSS observations and reanalysis estimates is 98%, while for IWV series it is 99%. That is, mesoscale fluctuations in zenith tropospheric delay, which are not taken into account in the reanalysis model, account for no more than 4% of its variance.

Meshcherova M.V., Khutorova O.G., Khutorov V.E. Comparison of zenith tropospheric delay based on GNSS and ERA5 reanalysis data in the Republic of Tatarstan. Electromagnetic waves and electronic systems. 2026. V. 31. № 3. P. 68−74. DOI: https://doi.org/10.18127/j15604128-202603-08 (in Russian)

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