01 Oct 2026
| 01 Oct 2026
Status: this preprint is open for discussion and under review for Natural Hazards and Earth System Sciences (NHESS).
Brief communication: GNSS water-vapour fluctuations read the air mass of the 2024 Rio Grande do Sul and 2022 Recife floods hours ahead of the heaviest rain
Abstract. Satellite-positioning antennas measure the water vapour above them, and the minute-to-minute fluctuations of that measurement, usually smoothed away, describe how the moisture is arranged. We read them at eleven Brazilian antennas during two floods with little or no radar coverage, in Rio Grande do Sul in 2024 and at Recife in 2022, against six-hourly rain gauges. Over a season they separate wet from dry periods 6 to 12 hours ahead, with an area under the receiver operating characteristic curve of 0.80 to 0.87. In both floods the antennas rose into their top 5% hours before the worst rain.
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