Exploring Non-tidal Atmospheric Loading Deformation Correction in GNSS Time Series Analysis Using GAMIT/GLOBK Software

This study investigates the effects of non-tidal atmospheric loading on GNSS time series for a network covering the Nordic countries, with a specific focus on Finland. We processed a 5-month dataset from the year 2015 using GAMIT/GLOBK software, implementing two distinct non-tidal atmospheric loading grid models, namely ‘atmfilt’ and ‘atmdisp’. Our results reveal that both grid models yield similar improvements in the variability of GNSS coordinate time series, albeit with a slightly better performance for ‘atmdisp’ grid. Our results show that implementing these built-in models in the time series analysis yields up to a 14% improvement (reduction in scatter) in the vertical component for 75% of the selected stations. However, the enhancement diminishes for the horizontal components (increase in scatter), exacerbating the eastern component of time series. The corrections lead to a 10% improvement of the North component. We also examined the effectiveness of the loading corrections by comparing our processing-level corrected time series to the daily averaged time series improved by the loading model provided by EOST loading service as a post-processing approach. Given the relatively short 5-month duration of the time series, drawing definitive conclusions when comparing models is challenging. However, it is evident that the GNSS time series exhibits distinct variations related to atmospheric loading in their vertical positions across the various models that were examined.