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Article

A Comparison between One-Step and Two-Step Nesting Strategy in the Dynamical Downscaling of Regional Climate Model COSMO-CLM at 2.2 km Driven by ERA5 Reanalysis

Regional Model and geo-Hydrological Impacts (REMHI), Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici, Via Thomas Alva Edison, 81100 Caserta, Italy
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Academic Editor: Rowan Fealy
Atmosphere 2021, 12(2), 260; https://doi.org/10.3390/atmos12020260
Received: 23 December 2020 / Revised: 10 February 2021 / Accepted: 12 February 2021 / Published: 16 February 2021
Recently, the European Centre for Medium Range Weather Forecast (ECMWF) has released a new generation of reanalysis, acknowledged as ERA5, representing at the present the most plausible picture for the current climate. Although ERA5 enhancements, in some cases, its coarse spatial resolution (~31 km) could still discourage a direct use of precipitation fields. Such a gap could be faced dynamically downscaling ERA5 at convection permitting scale (resolution < 4 km). On this regard, the selection of the most appropriate nesting strategy (direct one-step against nested two-step) represents a pivotal issue for saving time and computational resources. Two questions may be raised within this context: (i) may the dynamical downscaling of ERA5 accurately represents past precipitation patterns? and (ii) at what extent may the direct nesting strategy performances be adequately for this scope? This work addresses these questions evaluating two ERA5-driven experiments at ~2.2 km grid spacing over part of the central Europe, run using the regional climate model COSMO-CLM with different nesting strategies, for the period 2007–2011. Precipitation data are analysed at different temporal and spatial scales with respect to gridded observational datasets (i.e., E-OBS and RADKLIM-RW) and existing reanalysis products (i.e., ERA5-Land and UERRA). The present work demonstrates that the one-step experiment tendentially outperforms the two-step one when there is no spectral nudging, providing results at different spatial and temporal scales in line with the other existing reanalysis products. However, the results can be highly model and event dependent as some different aspects might need to be considered (i.e., the nesting strategies) during the configuration phase of the climate experiments. For this reason, a clear and consolidated recommendation on this topic cannot be stated. Such a level of confidence could be achieved in future works by increasing the number of cities and events analysed. Nevertheless, these promising results represent a starting point for the optimal experimental configuration assessment, in the frame of future climate studies. View Full-Text
Keywords: ERA5-reanalysis; COSMO-CLM; dynamical downscaling; precipitation; nesting strategy ERA5-reanalysis; COSMO-CLM; dynamical downscaling; precipitation; nesting strategy
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MDPI and ACS Style

Raffa, M.; Reder, A.; Adinolfi, M.; Mercogliano, P. A Comparison between One-Step and Two-Step Nesting Strategy in the Dynamical Downscaling of Regional Climate Model COSMO-CLM at 2.2 km Driven by ERA5 Reanalysis. Atmosphere 2021, 12, 260. https://doi.org/10.3390/atmos12020260

AMA Style

Raffa M, Reder A, Adinolfi M, Mercogliano P. A Comparison between One-Step and Two-Step Nesting Strategy in the Dynamical Downscaling of Regional Climate Model COSMO-CLM at 2.2 km Driven by ERA5 Reanalysis. Atmosphere. 2021; 12(2):260. https://doi.org/10.3390/atmos12020260

Chicago/Turabian Style

Raffa, Mario, Alfredo Reder, Marianna Adinolfi, and Paola Mercogliano. 2021. "A Comparison between One-Step and Two-Step Nesting Strategy in the Dynamical Downscaling of Regional Climate Model COSMO-CLM at 2.2 km Driven by ERA5 Reanalysis" Atmosphere 12, no. 2: 260. https://doi.org/10.3390/atmos12020260

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