Uncertainty produced in a 15-minute gridded rainfall product for the UK.

Reliable rainfall datasets are an essential foundation for hydrological research. The most extensive rainfall information is collected from rain gauge networks, which provide high-frequency observations on rainfall intensity at those locations, or their data can be interpolated onto a regular grid to provide consistent region-wide estimates.

For the UK, there are two major daily gridded rainfall products: (1) CEH-GEAR developed by the UK Centre for Ecology & Hydrology, and (2) HadUK-Grid developed by the Met Office. In each case, they are built from a selection of rain gauges from a multi-nation rain gauge network spanning Great Britain. Decisions made at each stage of rainfall data preparation, about collection, formatting, quality control and then gridding, introduce uncertainty into the resulting gridded rainfall products.

In this talk, we discuss plans for CEH-GEAR 15 min, a new sub-daily 1 km product developed as part of the UK’s multi-year Flood & Drought Research Infrastructure (FDRI) project. We detail each step of its production, from raw rain gauge to gridded rainfall estimates, and systematically discuss the sources of uncertainty introduced at each stage. 15-minute rainfall measurements tend to be highly variable in space and time, and intense storms or long dry periods create practical challenges for preparing gridded rainfall estimates. So, we quantify the sensitivity of those estimates to decisions made about quality control and data blending during notable rain events across the UK. We also present the associated open-source tools developed as part of FDRI, including RainfallQC, that aim to support reproducible rainfall data processing and alleviate some of the challenges in sub-daily rainfall data preparation.