Assessment of GNSS-based PWV against radiosonde observation and reanalysis datasets in Antarctica

Global warming phenomena lead to melting glaciers, rising sea levels, droughts, and irregular seasonal patterns, especially in polar regions. Besides, water vapor plays a significant role in these processes, contributing to about 60% of the natural greenhouse effect. Increasing temperature raises the atmosphere's capacity for water vapor, creating a positive feedback loop that aggravates global warming and extreme weather events. In polar regions, global warming is causing increased annual rainfall. Despite low overall precipitation, this phenomenon accelerates the melting of snow and ice, impacting local ecosystems. Future projections indicate that precipitation along Antarctica's coastline is expected to increase over the next 80 years. This increase may enhance surface melting through various processes. Consequently, monitoring atmospheric water vapor is crucial for understanding global climate dynamics and weather patterns. However, due to the harsh conditions in the polar regions, there is a shortage of conventional measurements, which makes global atmospheric reanalysis models crucial. The specific humidity and air pressure from the reanalysis models can be used to calculate Precipitable Water Vapor (PWV) (measured in meters), which is one of the most commonly used parameters for measuring atmospheric water vapor. Nevertheless, biases and discrepancies in the models may influence the data, particularly in polar regions where observations are scarce. In addition, the estimation of meteorological parameters can be acquired not only based on meteorological station data but also with the help of geodetic satellite data. Global Navigation Satellite Systems (GNSS) signals are subject to tropospheric refraction as they pass through the Earth's atmosphere, and the resulting zenith delays are divided into two components: hydrostatic (ZHD) and wet delay (ZWD). Moreover, the ZWD can be utilized to compute the PWV by multiplying a conversion factor. PWV can also be obtained by using air temperature and dew point temperature data from radiosonde observations at specific pressure levels. In this study, it is aimed to investigate and compare PWV values produced from GNSS-based, radiosonde-based, and global meteorological reanalysis models. Within the scope of the study, International GNSS Service (IGS) stations, which are located in the Antarctica continent, were used to calculate GNSS-based PWV. Besides, the radiosonde dataset retrieved from the Integrated Global Radiosonde Archive version 2.2 (IGRA 2.2) was used to obtain radiosonde-based PWV. As reanalysis datasets, the most recent reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF), and the National Aeronautics and Space Administration (NASA) were used. The fifth-generation reanalysis product from the ECMWF called ERA-5 and the second-generation version of NASA’s Modern-Era Retrospective analysis for Research and Applications called MERRA-2 data were used to obtain reanalysis based PWV. As a result of the study, root mean square errors (RMSE) and correlation values of GNSS-based PWV compared to radiosonde-based and reanalysis-based PWV were investigated for each IGS station. Besides, it was evaluated whether the GNSS technique could be used as an alternative to other methods in studies related to the troposphere and meteorology in the Antarctic continent.