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In this study, we evaluate a set of high-resolution (25–50 km horizontal grid spacing) global climate models (GCMs) from the High-Resolution Model Intercomparison Project (HighResMIP), developed as part of the EU-funded PRIMAVERA (Process-based climate simulation: Advances in high resolution modelling and European climate risk assessment) project, and from the EURO-CORDEX (Coordinated Regional Climate Downscaling Experiment) regional climate models (RCMs) (12–50 km horizontal grid spacing) over a European domain. It is the first time that an assessment of regional climate information using ensembles of both GCMs and RCMs at similar horizontal resolutions has been possible. The focus of the evaluation is on the distribution of daily precipitation at a 50 km scale under current climate conditions. Both the GCM and RCM ensembles are evaluated against high-quality gridded observations in terms of spatial resolution and station density. We show that both ensembles outperform GCMs from the 5th Coupled Model Intercomparison Project (CMIP5), which cannot capture the regional-scale precipitation distribution properly because of their coarse resolutions. PRIMAVERA GCMs generally simulate precipitation distributions within the range of EURO-CORDEX RCMs. Both ensembles perform better in summer and autumn in most European regions but tend to overestimate precipitation in winter and spring. PRIMAVERA shows improvements in the latter by reducing moderate-precipitation rate biases over central and western Europe. The spatial distribution of mean precipitation is also improved in PRIMAVERA. Finally, heavy precipitation simulated by PRIMAVERA agrees better with observations in most regions and seasons, while CORDEX overestimates precipitation extremes. However, uncertainty exists in the observations due to a potential undercatch error, especially during heavy-precipitation events. The analyses also confirm previous findings that, although the spatial representation of precipitation is improved, the effect of increasing resolution from 50 to 12 km horizontal grid spacing in EURO-CORDEX daily precipitation distributions is, in comparison, small in most regions and seasons outside mountainous regions and coastal regions. Our results show that both high-resolution GCMs and CORDEX RCMs provide adequate information to end users at a 50 km scale.

We have implemented dynamical downscaling of the Met Office GloSea5 global seasonal forecasting system and analysed its ability to generate skilful forecasts of characteristics of the June-September rainy season in Ethiopia that are of societal relevance. The downscaling used a regional model with a resolution of 25 km, and the same atmosphere and land configuration as the global model, to produce a 3-member ensemble of seasonal hindcasts for the period 1991–2011 and a larger 15-member ensemble for four of these years comprising two anomalously dry and two anomalously wet years. The regional model was also driven by the quasi-observed ERA-Interim dataset. To provide context for the assessment of the downscaled seasonal forecasts and to show the limit for the skill of a global seasonal forecast downscaling system for the region.A mainly qualitative assessment of GloSea5 and downscaled GloSea5 forecasts demonstrated that the downscaled forecasts could be considered a faithful disaggregation of the coarse resolution GloSea5 forecasts. Forecasts of average seasonal rainfall anomalies in the three regions of Ethiopia studied were captured in three of the four years with the wet season of 2006 incorrectly forecast in all three regions, and the 21 year 3-member hindcast had a correlation of 0.65 with observations. Whilst exploring the potential for the downscaled GloSea5 to generate skillful forecasts of rainy season onset and dry spells we note that both the global and regional model have skill with onset correctly predicted as being early or late in more than 75% of cases for some regions. Keywords: Seasonal forecast, Ethiopia, Downscaling, Rainy season onset, Dry spells