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CCLM - COSMO-ClimateLimited-areaModelling

COSMO - COnsortium for Small scale MOdeling

CLM-Logo.jpgWhat does the model do?

COSMO-CLM is a unified weather forecast and regional climate model. It out-puts a wide range of consistent climate parameters (about 100, scalable) including e.g. all components of the near-surface energy and water balance. Its deep-soil module TERRA_ML can handle permafrost. The lake model FLAKE can assess the impact of inland water bodies on the regional climate. It is a dynamic model, applicable for studying nonlinear feedback processes. In climate mode, it pro-vides scenarios at about 18 km grid resolution (e.g. the “Consortium runs”, see and below (recently: 10 km). In a new approach, it is applied to generate very-high resolution ensemble simulations for extremes (droughts and floods) under uncertainty with a spatial resolution of about 2.8 km. Temporal resolution is recently between 1 day and 1 hour with much smaller internal time steps (less than 10 min.). It is validated and inter-compared to other regional climate models (e.g. in the QUIRCS project) giving evidence of its high quality. Model regions cover recently Europe, Africa and India. It participated in EU projects as HYDROCARE, PRUDENCE and ENSEMBLES. Model regions cover Europe, Africa and India. Recent projects focus on resilient agro-landscapes to climate change in Eastern Africa (ReACCT), changes in weather-related insurance losses (German Insurance Association), on coupling climate-hydrology and on the im-pact of urban areas on regional climates. It contributes to the IPCC AR5 process within the CORDEX initiative (COordinated Regional Downscaling EXperiment).

Who maintains it?

The forecast part is maintained and developed by the COSMO consortium ( The climate part was originally developed at PIK (U. Böhm, F.-W. Gerstengarbe) and is now hosted and further developed commonly by the CLM community ( Recently, PIK provides essential contributions in adding further climate system components, in developing ensemble algorithms for extreme scenarios and in transferring the model to regions outside of Europe.

What are the next steps in the development of the model architecture?

In the next version 4.9, an aerosol module will be implemented (COSMO-ART). Also hail will be explicitly considered. OASIS-coupling to a regional ocean model will be enabled. A thermodynamic sea ice scheme is under construction. PIK focuses on two-way coupling of SWIM and CCLM to add retention and river routing to the ocean, plant dynamics and groundwater processes. An urban area model from NCAR is started to be implemented. Linking STAR and CCLM allows assess-ing both, frequency and intensity of extremes in a new approach.

In what way is the model different from other models in the community?

The model is a non-hydrostatic one with no scale approximations and applicable especially at very high resolutions of about 2.5 km. It is jointly developed by two international communities as an unified model. For the first time, an ensemble of regional scenarios for Europe is developed with CCLM to assess uncertainty.

Key publication

MetZ, Vol. 17, Number 4, August 2008: Special Issue on Regional Climate Modelling With COSMO-CLM (CCLM), Rockel et al., 347-348, Böhm et al., 477-485.

Poster SAB 2009

Poster Coupling of CCLM, STAR and SWIM

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