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.
Highlights
About 99% of the electromagnetic energy emitted by the Earth’s atmosphere system is distributed in the spectral range of 3–80 μm [1]
We explore the capability of the old and new permanent Global Navigation Satellite System (GNSS) stations installed in Arctic and Antarctic regions to provide reliable estimates of precipitable water vapour (PW)
This work is focused on the evaluation of Precipitable Water Vapour (PW) in the polar regions and on the estimation of its trend through the analysis of long time series from different sources
Summary
About 99% of the electromagnetic energy emitted by the Earth’s atmosphere system is distributed in the spectral range of 3–80 μm [1]. The water vapour, which strongly absorbs the radiation in this band [2,3,4,5], turns out to be an important component for the atmospheric radiative processes and for the evolution of the Earth’s climate. According to Lacis et al [6], the water vapour is responsible for 75% of the greenhouse effect. The water vapour was included in the list of Essential Climate Variables (ECV), contributing to the characterization of Earth’s climate according to the definition given by the Global Climate Observing System (GCOS). GCOS assesses the status of the global climate observations needed to support climate research and services
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