Abstract
There is an ongoing debate in the climate community about the benefits of convection-permitting models that explicitly resolve convection and other thermodynamical processes. An increasing number of studies show improvements in Regional Climate Model (RCM) performances when the grid spacing is increased to 1-km scale. Up until now, such studies have revealed that convection-permitting models confer significant advantages in representing orographic regions, producing high-order statistics, predicting events with small temporal and spatial scales, and representing convective organization. The focus of this work is on the analysis of summer precipitation over the Alpine space. More specifically, the driving data are downscaled using the RCM COSMO-CLM first at an intermediate resolution (12 km) over the European Domain of Coordinated Downscaling Experiment (EURO-CORDEX domain). Then, a further downscaling at 3 km, nested into the previous one, is performed over the Alpine domain to exploit the results over a complex orography context. Experiments of evaluation, historical and far future under the Intergovernmental Panel on Climate Change (IPCC) RCP8.5 scenario have been considered. Indices as mean precipitation, frequency, intensity, and heavy precipitation are employed in daily and hourly analyses. The results, observed from the analysis of 10 year-long simulations, provide preliminary indications, highlighting significant differences of the convection permitting simulations with respect to the driving one, especially at an hourly time scale. Moreover, future projections suggest that the convection permitting simulation refines and enhances the projected patterns, compared with the coarser resolution.
Highlights
At present, it is widely recognized that extreme precipitation is becoming more frequent and intense in warmer climates, in response to anthropogenic forcing [1,2]
The current study aims to contribute to such an open debate, in the climate community, by attempting to complete the following objectives: (i) Investigate behaviors and footprints yielded by a convection-parameterizing climate simulation and a convection-resolving one for summer precipitation at daily and hourly scales; (ii) Investigate potential changes in summer precipitation regimes, expected for the end of the century, resulting from the ongoing climate change; (iii) Prove limitations and benefits returned by a spatial and temporal refinement of CP-Regional Climate Model (RCM)
The ALP-3 simulation performs well the heavy precipitation (Figure 2b), slight overestimations indicate that some problems in initiating small-scale convective summer precipitation still persist over orography
Summary
It is widely recognized that extreme precipitation is becoming more frequent and intense in warmer climates, in response to anthropogenic forcing [1,2]. Extreme precipitation events are the main causes for different hazards (e.g., floods), and play an important role for engineers and hydrologists involved in the update of existing design standards of structures, such as dams, bridges, and sewage systems to potential future changes, as well as for land use planning and socioeconomic purposes [3,4]. Such evidence suggests the need to provide climate information at properly temporal (preferably hourly) and spatial (preferably ~1–3 km) scales, concerning current climate and future projections. The benefits in explicitly resolving convection and other (thermo)dynamical processes are appreciated from the climate community, only with recent computational advances that climate time scales (i.e., decade or longer) are within reach
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