The CORDEX project, endorsed by the World Climate Research Program (WCRP), provides global coordination of Regional Climate Downscaling (RCD) for improved regional climate change adaptation and impact assessment. In this framework, the MENA-CORDEX domain (27W – 76E, 7S – 45N), which includes North Africa, southern Europe and the whole Arabian peninsula, offers considerable challenges for assessing and understanding climate change over the region due to its large size and complex topography. In fact, it includes highland areas, wide coastal areas and desert areas. Increasing temperatures and changes in precipitation patterns make this region one of the most prominent climate change “hot spots”, with increased risks of heat mortality, energy and water shortage and crop failure. High-resolution climate projections within the MENA-CORDEX domain are driven by several needs, such as the assessment of impacts on water resources in the Arab region. Therefore, given the expected climate change conditions, an evaluation of the specific effects of climate change for the MENA countries in the medium and long term is of crucial importance with regard to the development of adaptation strategies.
The REMHI division of CMCC is massively involved in the MENA-CORDEX project. Several simulations with the regional model COSMO-CLM have been performed over this area. The activity is carried out in cooperation with the Karlsruher Institut für Technologie (Germany). Being this domain one of the last defined CORDEX official ones, the number of simulations already available is still limited. For this reason, in was necessary to perform a sensitivity analysis of the model with the aim of defining an optimal configuration for this complex and heterogeneous zone. The analysis shows significant improvements in the representation of the main climatic variables using a new albedo representation (which realistically describes the terrestrial surface reflectivity) and of the aerosols. Figure 1 shows the map of temperature bias for winter (DJF) and (summer (JJA) against CRU observational dataset, obtained respectively with the reference and the optimized configuration. Successively, control simulations over the past period 1979-2011 have been performed at different resolutions (0.44° and 0.22° according with CORDEX protocols) in order to quantify the performance improvement with the resolution. Performance evaluation of the two simulations highlights that for average precipitation and for the interannual variability of temperatures, a slight improvement is obtained adopting a higher resolution; moreover, in general the representation of extreme events takes a more evident advantage of the high resolution. Figure 2 shows the physical domain (black line) and the computational domain for 0.22° (blue line) and 0.44° (red line) resolution. Is currently in preparation the paper concerning the climate projections over the XXI (at the same spatial resolutions) according with the IPCC RCP4.5 scenario and forced by the global model CMCC-CM (Bucchignani et al., in preparation). Since the number of projections for this area is still limited, these simulations represent a valuable contribution to the definition of robust scenarios for this area. The reliability of projections might be improved by using multi-model ensembles, which are useful for uncertainty quantification. Of course, ensembles must use a common framework to achieve robust and useful conclusions in projecting future regional climate change, as addressed by the CORDEX initiative.
Bucchignani E., Cattaneo L., Panitz H.-J., Mercogliano P. (2015) Sensitivity analysis with the regional climate model COSMO-CLM over the CORDEX-MENA domain. Meteorology and Atmospheric Physics DOI: 10.1007/s00703-015-0403-3
Bucchignani E., Mercogliano P., Rianna G., Panitz H.J. (2015) – Analysis of ERA-Interim-driven COSMO-CLM simulations over Middle East – North Africa domain at different spatial resolutions – International Journal Of Climatology DOI: 10.1002/joc.4559