| 20 Apr 2026
A multi-year dataset of integrated water vapor derived from shipborne GNSS observations collected aboard eight French research vessels during oceanographic campaigns (2015–2024)
Abstract. In the context of climate change and the growing need for improved observations of the atmospheric water cycle, measurements of atmospheric water vapor over the global ocean remain scarce compared with those available over land. This observational gap can be addressed using Integrated Water Vapor (IWV) derived from shipborne Global Navigation Satellite System (GNSS) observations, which provide a robust and well-established method for monitoring atmospheric moisture over the oceans.
This study presents a shipborne IWV dataset obtained from the processing of raw data collected by GNSS antennas installed on research vessels. The dataset benefits from substantial support and data access provided by Genavir, the operator of the French Oceanographic Fleet (FOF), and the Ifremer archive department SISMER. It is based on oceanographic campaigns conducted worldwide by eight vessels over a ten-year period (2015–2024), representing a total of 6,427 campaign days in both offshore and coastal regions.
After describing the methodology used to derive IWV from raw GNSS observations and to remove spurious measurements through a screening procedure, the dataset is evaluated through comparisons with the ERA5 reanalysis and satellite radiometer measurements from Remote Sensing Systems. These comparisons yield mean differences of (0.3 ± 2.0) kg m−2 and (−0.4 ± 1.8) kg m−2, respectively.
To further quantify the inherent uncertainty of the shipborne IWV retrieval, the dataset is cross-validated using instances where two vessels were within 50 km of each other. This comparison results in an estimated uncertainty of 0.96 kg m−2, demonstrating the suitability of the dataset for climate studies.
Local discrepancies identified in these comparisons are discussed, highlighting limitations in each dataset considered.
The GNSS-derived IWV dataset is intended to be updated annually to support long-term monitoring of atmospheric water vapor over the global ocean.
The IWV estimates are available at https://doi.org/10.25326/876 (Panetier and Bosser, 2026) through the AERIS data center (https://en.aeris-data.fr/, last access: 20 March 2026), and currently span the period from 2015 to the end of 2024.
