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Vautard, R., Gobiet, A., Jacob, D., Belda, M., Colette, A., Deque, M., . . . Yiou, P. (2013). The simulation of European heat waves from an ensemble of regional climate models within the EURO-CORDEX project. Climate Dynamics, 41(9-10), 2555-2575
Open this publication in new window or tab >>The simulation of European heat waves from an ensemble of regional climate models within the EURO-CORDEX project
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2013 (English)In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 41, no 9-10, p. 2555-2575Article in journal (Refereed) Published
Abstract [en]

The ability of a large ensemble of regional climate models to accurately simulate heat waves at the regional scale of Europe was evaluated. Within the EURO-CORDEX project, several state-of-the art models, including non-hydrostatic meso-scale models, were run for an extended time period (20 years) at high resolution (12 km), over a large domain allowing for the first time the simultaneous representation of atmospheric phenomena over a large range of spatial scales. Eight models were run in this configuration, and thirteen models were run at a classical resolution of 50 km. The models were driven with the same boundary conditions, the ERA-Interim re-analysis, and except for one simulation, no observations were assimilated in the inner domain. Results, which are compared with daily temperature and precipitation observations (ECA&D and E-OBS data sets) show that, even forced by the same re-analysis, the ensemble exhibits a large spread. A preliminary analysis of the sources of spread, using in particular simulations of the same model with different parameterizations, shows that the simulation of hot temperature is primarily sensitive to the convection and the microphysics schemes, which affect incoming energy and the Bowen ratio. Further, most models exhibit an overestimation of summertime temperature extremes in Mediterranean regions and an underestimation over Scandinavia. Even after bias removal, the simulated heat wave events were found to be too persistent, but a higher resolution reduced this deficiency. The amplitude of events as well as the variability beyond the 90th percentile threshold were found to be too strong in almost all simulations and increasing resolution did not generally improve this deficiency. Resolution increase was also shown to induce large-scale 90th percentile warming or cooling for some models, with beneficial or detrimental effects on the overall biases. Even though full causality cannot be established on the basis of this evaluation work, the drivers of such regional differences were shown to be linked to changes in precipitation due to resolution changes, affecting the energy partitioning. Finally, the inter-annual sequence of hot summers over central/southern Europe was found to be fairly well simulated in most experiments despite an overestimation of the number of hot days and of the variability. The accurate simulation of inter-annual variability for a few models is independent of the model bias. This indicates that internal variability of high summer temperatures should not play a major role in controlling inter-annual variability. Despite some improvements, especially along coastlines, the analyses conducted here did not allow us to generally conclude that a higher resolution is clearly beneficial for a correct representation of heat waves by regional climate models. Even though local-scale feedbacks should be better represented at high resolution, combinations of parameterizations have to be improved or adapted accordingly.

Keywords
Regional climate modeling, Heat waves, Model evaluation, Climate projection, EURO-CORDEX
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-342 (URN)10.1007/s00382-013-1714-z (DOI)000326244700019 ()
Available from: 2015-04-14 Created: 2015-03-31 Last updated: 2017-12-04Bibliographically approved
Nikulin, G., Jones, C., Giorgi, F., Asrar, G., Buechner, M., Cerezo-Mota, R., . . . Sushama, L. (2012). Precipitation Climatology in an Ensemble of CORDEX-Africa Regional Climate Simulations. Journal of Climate, 25(18), 6057-6078
Open this publication in new window or tab >>Precipitation Climatology in an Ensemble of CORDEX-Africa Regional Climate Simulations
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2012 (English)In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 25, no 18, p. 6057-6078Article in journal (Refereed) Published
Abstract [en]

An ensemble of regional climate simulations is analyzed to evaluate the ability of 10 regional climate models (RCMs) and their ensemble average to simulate precipitation over Africa. All RCMs use a similar domain and spatial resolution of similar to 50 km and are driven by the ECMWF Interim Re-Analysis (ERA-Interim) (1989-2008). They constitute the first set of simulations in the Coordinated Regional Downscaling Experiment in Africa (CORDEX-Africa) project. Simulated precipitation is evaluated at a range of time scales, including seasonal means, and annual and diurnal cycles, against a number of detailed observational datasets. All RCMs simulate the seasonal mean and annual cycle quite accurately, although individual models can exhibit significant biases in some subregions and seasons. The multimodel average generally outperforms any individual simulation, showing biases of similar magnitude to differences across a number of observational datasets. Moreover, many of the RCMs significantly improve the precipitation climate compared to that from their boundary condition dataset, that is, ERA-Interim. A common problem in the majority of the RCMs is that precipitation is triggered too early during the diurnal cycle, although a small subset of models does have a reasonable representation of the phase of the diurnal cycle. The systematic bias in the diurnal cycle is not improved when the ensemble mean is considered. Based on this performance analysis, it is assessed that the present set of RCMs can be used to provide useful information on climate projections over Africa.

National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-436 (URN)10.1175/JCLI-D-11-00375.1 (DOI)000309038000001 ()
Available from: 2015-04-21 Created: 2015-04-14 Last updated: 2017-12-04Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3483-0008

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