Global precipitation gauge coverage and siting priorities

The study evaluates precipitation-gauge coverage because reliable climate projections and water-deficiency assessments require observations that are spatially comprehensive and temporally complete. It evaluates 221,483 internationally exchanged precipitation gauges with records spanning 1900–2022 and explores where new gauges are most needed under different scenarios. Only 13.4% of global land surface currently meets World Meteorological Organization requirements for annual precipitation monitoring. Europe has the highest continental gauge density, at 2.4 gauges per 1,000 square kilometres, while Germany leads among countries larger than 50,000 square kilometres. One quarter of global land surface already requires urgent network expansion because of climate variability. When projected precipitation changes and socioeconomic conditions under a high-emission scenario are considered, high-need regions expand to 32.1% of global land, including regions in India, Greenland, Bolivia and China. The authors conclude that global precipitation monitoring has important gaps requiring strategic investment and open data access.

Between 1900 and 2022, the study compiled observations from 221,483 accessible precipitation gauges, of which 63.2%, or 139,901, remained active within the past 30 years. It identified 38,203 long-term-record stations, defined as records spanning more than 30 years with less than 10% missing data. Only 16,491 of 119,731 operating stations in 2022 were long-term-record stations. Europe had the largest share of long-term-record stations, while Africa had very low total and long-term station densities. Comparing gauge density with World Meteorological Organization requirements, only 13.4% of global land met recommended station density during 1900–2022, and only 1.9% met the requirement when long-term-record stations alone were considered. The analysis attributes insufficient density to limited public data accessibility, high construction and maintenance costs, data-quality challenges and lower prioritization in regions perceived as having limited climate risks.

Using a priority score for siting new gauges, the study identifies approximately 25% of global land as high priority under historical precipitation information from 1900 to 2022. High-priority land shares include 38.7% of Africa, 32.3% of South America and 33.6% of Europe. The priority framework combines gauge density with precipitation spatial variability. Under future scenarios, it incorporates projected precipitation, population and gross domestic product. Considering future precipitation and socioeconomic conditions from 2025 to 2100, 32.1% of global land is high priority under SSP5-8.5, compared with 17.7% under SSP1-2.6. Under SSP5-8.5, the high-priority share reaches 54.9% of Africa and 39.3% of South America, while Europe, Asia and North America also expand because of socioeconomic factors. The authors identify 171 countries as urgently needing new gauges under SSP5-8.5.