Sub-hourly precipitation over a Mediterranean catchment in a high-resolution climate model

18:00 Tuesday 28 May




Edmund Meredith (Germany) 1; Edmund Ulbrich (Germany) 1; Henning Rust (Germany) 1

1 - Freie Universität Berlin

Convection-permitting atmospheric models [O (1 km)] add value to lower-resolution models for the simulation of extreme precipitation, in particular for short-duration (i.e. sub-daily) extremes of a convective nature. Such events are the main cause of flash flooding, an acute risk in many regions. Accurate modelling of short-duration rainfall events in the present climate is thus key for having confidence in future projections of how the flash-flooding risk may change. As such, evaluation of short-duration (extreme) precipitation in convection-permitting models is an important endeavour. Owing to a lack of observational datasets at both high spatial and temporal resolution, however, most evaluations of convection-permitting models have to date been at the hourly (or longer) temporal scale. The validation of precipitation in convection-permitting models at the sub-hourly scale has thus been identified as an important challenge for climate science (e.g. Chan et al., 2016).

Using a unique regional micro-gauge network from the Mediterranean city of Barcelona, with 5-minute precipitation observations spanning on average 20 years, we analyse the performance of the COSMO-CLM climate model at 2 km resolution in simulating the characteristics – both mean and extreme – of observed precipitation during this period. Results indicate that the model simulates 5-minute and sub-hourly precipitation with comparable realism to that found at the hourly scale, suggesting that convection-permitting models can be a valuable tool for the study of sub-hourly precipitation extremes.

Our results offer useful guidance to researchers on working with and interpreting high-resolution (temporal and spatial) modelled precipitation, or planning related experiments.

References: Chan, SC, EJ Kendon, NM Roberts, HJ Fowler and S Blenkinsop (2016). The characteristics of summer sub-hourly rainfall over the southern UK in a high-resolution convective permitting model. Environmental Research Letters, 11(9): 094024.