Water Vapour Assessment Using GNSS and Radiosondes over Polar Regions and Estimation of Climatological Trends from Long-Term Time Series Analysis

Abstract

The atmospheric humidity in the Polar Regions is an important factor for the global budget of water vapour, which is a significant indicator of Earth’s climate state and evolution. The Global Navigation Satellite System (GNSS) can make a valuable contribution in the calculation of the amount of Precipitable Water Vapour (PW). The PW values retrieved from Global Positioning System (GPS), hereafter PWGPS, refer to 20-year observations acquired by more than 40 GNSS geodetic stations located in the polar regions. For GNSS stations co-located with radio-sounding stations (RS), which operate Vaisala radiosondes, we estimated the PW from RS observations (PWRS). The PW values from the ERA-Interim global atmospheric reanalysis were used for validation and comparison of the results for all the selected GPS and RS stations. The correlation coefficients between times series are very high: 0.96 for RS and GPS, 0.98 for RS and ERA in the Arctic; 0.89 for RS and GPS, 0.97 for RS and ERA in Antarctica. The Root-Mean-Square of the Error (RMSE) is 0.9 mm on average for both RS vs. GPS and RS vs. ERA in the Arctic, and 0.6 mm for RS vs. GPS and 0.4 mm for RS vs. ERA in Antarctica. After validation, long-term trends, both for Arctic and Antarctic regions, were estimated using Hector scientific software. Positive PWGPS trends dominate at Arctic sites near the borders of the Atlantic Ocean. Sites located at higher latitudes show no significant values (at 1σ level). Negative PWGPS trends were observed in the Arctic region of Greenland and North America. A similar behaviour was found in the Arctic for PWRS trends. The stations in the West Antarctic sector show a general positive PWGPS trend, while the sites on the coastal area of East Antarctica exhibit some significant negative PWGPS trends, but in most cases, no significant PWRS trends were found. The present work confirms that GPS is able to provide reliable estimates of water vapour content in Arctic and Antarctic regions too, where data are sparse and not easy to collect. These preliminary results can give a valid contribution to climate change studies.

First Retrievals of Surface and Atmospheric Properties Using EnMAP Measurements over Antarctica

“…The same arguments as explained above can be applied to other trace gases, including ozone. In particular, we could derive the total ozone column (TOC) using arguments similar to those used to obtain Equation (22) [31,45]:…”

“…Thus, water vapor is a second source of warmth (in addition to sunlight) at the Antarctic surface. The atmosphere in inner Antarctica is very dry with values of PWV around 0.4-0.5 mm on average [20][21][22].…”

Review of Environmental Monitoring by Means of Radio Waves in the Polar Regions: From Atmosphere to Geospace

“…A climatological study of PW in the polar regions by Negusini et al (2021), was based on the 20-year time series (1998-2017) of GPS observations, acquired, among the others, at five coastal Antarctic and Arctic stations as mapped in Fig. 9.…”

First Retrievals of Surface and Atmospheric Properties Using EnMAP Measurements over Antarctica

“…Thus, water vapor is a second source of warmth (in addition to sunlight) at the Antarctic surface. The atmosphere in inner Antarctica is very dry with values of PWV around 0.4 -0.5mm on average [20][21][22].…”