A multi‐year assessment of sub‐hourly gridded precipitation for Switzerland based on a blended radar—rain‐gauge dataset

Blended high‐resolution sub‐hourly precipitation fields are increasingly needed for nowcasting and automatic warnings systems. Here we present a 7‐year (2012–2018) assessment of (5‐min) precipitation characteristics for the topographically complex region of Switzerland. We use CombiPrecip, a blended radar—rain‐gauge product that provides high resolution (1 km2) hourly precipitation fields. Five‐minute fields (CPCD), fine enough to disentangle even the shortest convective events from longer‐lasting precipitation, are obtained by temporally disaggregating these hourly fields. A rain‐gauge verification of the sub‐hourly precipitation fields shows that CPCD out‐performs the radar‐only estimates both in terms of quantitative error and in detecting wet/extreme periods, making CPCD sufficiently accurate to be used with confidence as input fields for hydrological modelling or for regional model validation. The quantitative error of CombiPrecip at the 60 (10)‐min time‐scale, as expressed by the scatter, is 40% (22%) lower than that of the radar‐only product. Radar‐gauge discrepancies are large and the quantitative error of CPCD increases by 30% when decreasing aggregation times from 60 to 10 min. Although summertime 5‐min precipitation extremes are strongest and more frequent on average south of the Alps, where they contribute to approximately 10% of the seasonal total precipitation, the most intense extremes are observed over the Jura Mountains in the afternoon and the highest wet 5‐min frequency in the Prealps around the same time. Intense precipitation is more evenly distributed throughout the day south of the Alps. Extreme intensity and frequency peaks 2 hr earlier in the Prealps, the Jura Mountains and the Alps (~1600 UTC) compared to the Swiss Plateau (~1800 UTC). Extremes are less intense and frequent at high elevations (>2,000 MASL) than over the Swiss Plateau (<800 MASL).