Abstract

Most studies linking atmospheric water vapor and precipitation emphasize short records, tropical regions, or the Northern Hemisphere. Long-term variability of water vapor and its coupling with precipitation remain poorly understood across strong latitudinal and climatic gradients. Here we analyze 15–27 years of precipitable water vapor (PWV) from Global Navigation Satellite Systems (GNSS) and co-located rain gauges across southwestern South America. The strength of PWV–precipitation coupling varies systematically with latitude and precipitation regime: high-elevation convective regions show strong coupling across timescales, while extratropical areas dominated by stratiform precipitation exhibit weaker annual and monthly but moderate daily relationships. Seasonal PWV ranges from (Formula presented.) 40 mm in the tropics to (Formula presented.) 6 mm in subpolar regions, yet precipitation varies inversely. Probability distributions reveal a power-law PWV–precipitation relationship only in the tropical Andes, whereas extratropical regions follow a logistic form shaped by positively skewed PWV. © 2025 The Author(s).