At CMCC, the regional climate model COSMO-CLM (Rockel and Geyer, 2008) is currently used to perform dynamical downscaling of global climate simulations (see figure 1).

Figure 1: A RCM domain embedded in a GCM grid. Image source F. Giorgi, 2008.

COSMO-CLM it is the climate version of the COSMO LM model (Steppeler et al., 2003), which is the operational non-hydrostatic mesoscale weather forecast model developed initially by the German Weather Service (DWD) and then by the European Consortium COSMO. The RCM COSMO CLM is currently developed by the CLM-Community, with which CMCC collaborates since 2008.

COSMO CLM is employed at spatial resolution between 1 and 50 km; these values are usually close to those requested by the impact modelers; in fact, they allow describing more correctly the terrain orography with respect to global models.
Moreover the non-hydrostatic formulation provides a better description of the convective phenomena (Holton, 2004), which are generated by vertical movement of the properties of the fluid as energy, water vapor and momentum. Convection can redistribute significant amounts of moisture, heat and mass on small temporal and spatial scales; furthermore, convection can cause severe localized precipitation events (as thunderstorm or cluster of thunderstorms).

The mathematical formulation of COSMO CLM is based on the fluid dynamics equations for a compressible flow. The atmosphere is treated as a multicomponent fluid (made up of dry air, water vapor, liquid and solid water) for which the perfect gas equation holds, and subject to the gravity and to the Coriolis forces. The prognostic variables are the following: horizontal and vertical Cartesian wind components, pressure perturbation, temperature, specific humidity, cloud water content, cloud ice content, turbulent kinetic energy and specific water content of rain, snow and graupel. The model includes several parameterizations, in order to keep into account, at least in a statistical manner, several phenomena that take place on unresolved scales, but that have significant effects on the meteorological interest scales:

• Sub grid-Scale Turbulence
  – Surface Layer Parameterization
  – Grid-Scale Clouds and Precipitation
  – Sub grid-Scale Clouds
  – Moist Convection
  – Shallow Convection
  – Radiation
  – Soil Model
  – Terrain and Surface Data
• Urban parameterization (TERRA-URB)

At CMCC, COSMO-CLM was driven by both reanalysis (i.e. ERA-Interim) and by Global Models (CMCC-CM, EC-Earth) and has been used in the frame of several national and international projects:

• ADAPTALP Interreg (Adaptation to climate change in the Alpine space): climate projections at 8 km resolution over the XXI century for the Alpine space, under IPCC RCP4.5 and RCP8.5 scenarios.
• GEMINA (F.I.S.R. – CIPE n. 42/2010) of CMCC): climate projections at 8 km resolution over the XXI century for Italy, under IPCC RCP4.5 and RCP8.5 scenarios. Climate projections at 14 km resolution over the XXI century for a wide Chinese region, under IPCC RCP4.5 and RCP8.5 scenarios.
• CLUVA (FP7 – Env 2010) Climate Change and Urban Vulnerability in Africa: Climate projections at 14 km resolution over the XXI century for selected African areas.
• MENA-CORDEX: Climate projections at 50 and 25 km resolution over the XXI century for the Middle East North Africa domain, under IPCC RCP4.5 scenario.
• ALCOTRA-CLIMAERA: Climate projections at high resolution for selected European domains and selected periods under IPCC RCP4.5 scenario
• CORDEX-CORE FPS Convection (Very high-resolution convection permitting simulations including TERRA-URB parameterization) and Lucas (Land Use and Climate Across Scales).
• EUCP (European Climate Prediction system) aimed to investigate convective-scale events, their processes and their changes in a few key regions of Europe and the Mediterranean, using convection-permitting RCMs
• Many other projects, such as PERSEUS (FP7 – Ocean 2011-3), LIFE TRUST, LIFE-SALT, FUME (FP7 – Environment), PNACC, DRR MAURITIUS.

For more information about the COSMO CLM model and the CLM-Community see the webpage: https://www.clm-community.eu/

A list of the main publications on refereed journals published by CMCC using COSMO-CLM is reported here:

• Bucchignani E., M. Montesarchio, L. Cattaneo, M. Manzi, P. Mercogliano, Regional Climate modeling over China with COSMO-CLM: performance assessment and climate projections, Journal of Geophysical Research, 119(21), 12151-12170, 2014. DOI: 10.1002/2014JD022219
• Montesarchio M., A. Zollo, E. Bucchignani, P. Mercogliano, S. Castellari, Performance evaluation of high-resolution regional climate simulations in the Alpine space and analysis of extreme events, Journal of Geophysical Research, 119, 3222–3237, 2014. DOI: 10.1002/2013JD021105
• Bucchignani E, Montesarchio M, Zollo AL, Mercogliano P, “High-resolution climate simulations with COSMO-CLM over Italy: performance evaluation and climate projections for the XXI century”, DOI: 10.1002/joc.4379, International Journal of Climatology, Vol 36 Issue 2, 2016, pp. 735-756.
• Zollo AL, Rillo V, Bucchignani E, Montesarchio M, Mercogliano, “Extreme temperature and precipitation events over Italy: assessment of high resolution simulations with COSMO-CLM and future scenarios”, DOI: 10.1002/joc.4401, International Journal of Climatology, Vol 36 Issue 2, 2016, pp. 987-1005.
• Bucchignani E, Cattaneo L, Panitz H-J, Mercogliano P, “Sensitivity analysis with the regional climate model COSMO-CLM over the CORDEX-MENA domain”. DOI: 10.1007/s00703-015-0403-3, Meteorology and Atmospheric Physics, Vol 128 Issue 1, 2016, pp. 73-95.
• Bucchignani E, Zollo AL, Cattaneo L, Montesarchio M, Mercogliano P, “Extreme weather events over China: assessment of COSMO CLM simulations and future scenarios”, DOI: 10.1002/joc.4798, International Journal of Climatology, Vol 37 Issue 3, 2016, pp. 1578-1594.
• Bucchignani E, Mercogliano P, Rianna G, Panitz HJ, “Analysis of ERA-Interim-driven COSMO-CLM simulations over Middle East – North Africa domain at different spatial resolutions”, DOI: 10.1002/joc.4559, International Journal Of Climatology Vol 36 Issue 9, 2016, pp. 3346-3369.
• Bucchignani E, Mercogliano P, Panitz HJ, Montesarchio M, “Climate change projections for the Middle East – North Africa domain with COSMO-CLM at different spatial resolutions”, DOI: 10.1016/j.accre.2018.01.004, Advances in Climate Change Research, Vol 9 Issue 1, 2018, pp. 66-80.

Research papers:

• RP0088 – Climatic study of precipitation and temperature distribution over the Alps and the Italian Peninsula, using the High-Resolution Regional Climate Model COSMO-CLM
• RP0136 – Prearrangement of the COSMO-CLM Model on the Chinese region and sensitivity analysis
• RP0137 – Performance evaluation of a regional climate simulation with COSMO-CLM in the Alpine space
• RP0143 – A sensitivity study with the RCM COSMO CLM over the north and center Italy
• RP0144 – Assessment of COSMO-CLM performances over Mediterranean Area
• RP0145 – Assessment of COSMOCLM performances in simulating the past climate of Italy
• RP0171 – Post-processing methods for COSMO-CLM precipitation over Italy
• RP0179 – GCM driven COSMO-CLM post-processed precipitation over Italy: control and future scenarios
• RP0181 – Simulation of the period 1979-2011 over China with the regional climate model COSMO-CLM
• RP0183 – Assessment of ERA-Interim driven simulation over Italy with COSMO-CLM
• RP0184 – A simulation over the Mediterranean area with COSMO-CLM: assessment of the performance
• RP0233 – High resolution climate scenarios on Mediterranean test case areas for the hydro-climate integrated system
• RP0238 – Performance analysis of the COSMO-CLM model

References

• Giorgi, F. (2008). Regionalization of climate change information for impact assessment and adaptation. WMO Bulletin 57 (2) – April 2008, 86 – 92. Retrieved April 15th, 2014 from https://www.wmo.int/pages/publications/bulletin_en/archive/57_2_en/documents/giorgi_sub_en.pdf
• Holton, J.R. (2004). An Introduction to Dynamic Meteorology, Academic Press, International Geophysics Series Volume 88, Fourth Edition, 535 p., ISBN 0-12-354015-1, ISBN 978-0-12-354015-7
• Rockel, B., and B. Geyer (2008).The performance of the regional climate model CLM in different Climate regions, based on the example of precipitation, Meteorologische Zeitschrift, 17(4), 487– 498.
• Steppeler, J., G. Doms, U. Schättler, H. Bitzer, A. Gassmann, U. Damrath, and G. Gregoric (2003), Meso-gamma scale forecasts using the nonhydrostatic model LM, Meteorol. Atmos. Phys., 82, 75-96