Articles | Volume 34, issue 7
Regular paper
20 Jul 2016
Regular paper |  | 20 Jul 2016

Multi-year GNSS monitoring of atmospheric IWV over Central and South America for climate studies

Clara Eugenia Bianchi, Luciano Pedro Oscar Mendoza, Laura Isabel Fernández, María Paula Natali, Amalia Margarita Meza, and Juan Francisco Moirano

Abstract. Atmospheric water vapour has been acknowledged as an essential climate variable. Weather prediction and hazard assessment systems benefit from real-time observations, whereas long-term records contribute to climate studies. Nowadays, ground-based global navigation satellite system (GNSS) products have become widely employed, complementing satellite observations over the oceans. Although the past decade has seen a significant development of the GNSS infrastructure in Central and South America, its potential for atmospheric water vapour monitoring has not been fully exploited. With this in mind, we have performed a regional, 7-year-long and homogeneous analysis, comprising 136 GNSS tracking stations, obtaining high-rate and continuous observations of column-integrated water vapour and troposphere zenith total delay. As a preliminary application for this data set, we have estimated local water vapour trends, their significance, and their relation with specific climate regimes. We have found evidence of drying at temperate regions in South America, at a rate of about 2 % per decade, while a slow moistening of the troposphere over tropical regions is also weakly suggested by our results. Furthermore, we have assessed the regional performance of the empirical model GPT2w to blindly estimate troposphere delays. The model reproduces the observed mean delays fairly well, including their annual and semi-annual variations. Nevertheless, a long-term evaluation has shown systematical biases, up to 20 mm, probably inherited from the underlying atmospheric reanalysis. Additionally, the complete data set has been made openly available as supplementary material.

Short summary
Long-term monitoring of the amount of water vapour in the lower atmosphere is essential for climate studies. We analysed satellite observations, at hundreds of locations in Central and South America, to look for changes in this parameter over several years. We found evidence of drying of the troposphere in temperate regions, and also evidence of slow moistening over the tropics. Moreover, we openly provide the complete data collection to the scientific community.