COSMO-CLM Regional Climate Simulations in the CORDEX framework: a review

Abstract

Abstract. In the last decade, the Climate Limited-area Modeling (CLM) Community has contributed to the Coordinated Re- gional Climate Downscaling Experiment (CORDEX) with an extensive set of regional climate simulations. Using several versions of the COSMO-CLM community model, ERA-Interim reanalysis and eight Global Climate Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) were dynamically downscaled with horizontal grid spacings of 0.44° (∼50 km), 0.22° (∼25 km) and 0.11° (∼12 km) over the CORDEX domains Europe, South Asia, East Asia, Australasia and Africa. This major effort resulted in 80 regional climate simulations publicly available through the Earth System Grid Fed- eration (ESGF) web portals for use in impact studies and climate scenario assessments. Here we review the production of these simulations and assess their results in terms of mean near-surface temperature and precipitation to aid the future design of the COSMO-CLM model simulations. It is found that a domain-specific parameter tuning is beneficial, while increasing horizontal model resolution (from 50 to 25 or 12 km grid spacing) alone does not always improve the performance of the simulation. Moreover, the COSMO-CLM performance depends on the driving data. This is generally more important than the dependence on horizontal resolution, model version and configuration. Our results emphasize the importance of performing regional climate projections in a coordinated way, where guidance from both the global (GCM) and regional (RCM) climate modelling communities is needed to increase the reliability of the GCM-RCM modelling chain.

Projected future daily characteristics of African precipitation based on global (CMIP5, CMIP6) and regional (CORDEX, CORDEX-CORE) climate models

“…In this paper we focus on daily characteristics of precipitation. However, useful regional climate information can be constructed also by analyzing model results for pre- Panitz et al (2014), Sørland et al (2021) claim that boundary conditions may affect the results more critically than model version, configuration and horizontal resolution. 5.…”

Sensitivity of Convection Permitting Simulations to Lateral Boundary Conditions in Idealized Experiments

“…Anyhow, it is recommended to use a driving model with grid‐spacing scales not too deep in the gray zone of its convection parameterization. Direct nesting of a CPM with grid‐spacing of 4.9 km or finer into, for example, global ERA5 re‐analysis data (Hersbach et al., 2020), global HighResMIP (Haarsma et al., 2016), or regional CORDEX‐CORE (Sørland et al., 2021) simulations with about 30–25 km grid‐spacing is sensible given the results shown here. Nesting into an intermediate gray‐zone nest is not advised.…”

“…The nonhydrostatic LAM COSMO‐CLM (e.g., Rockel et al., 2008) in version COSMO5.0‐CLM7 was applied in the idealized test configurations. COSMO‐CLM has been used successfully in many climate studies with typical grid‐spacings from $$\sim 50$$ km to convection‐permitting scales with grid‐spacing of $$\mathcal{O}(1\,\mathrm{k}\mathrm{m})$$ (Purr et al., 2021; Sørland et al., 2021). Necessary initial and lateral boundary data were compiled with the pre‐processor INT2LM2.0‐CLM4.…”

“…In CORDEX (Coordinated REgional Climate Downscaling Experiment), for example, a default grid‐spacing of about 50 km was suggested to be used in multiple domains covering all global continents (https://cordex.org/, Giorgi et al. (2009)), but finer grid‐spacing was already suggested and later on used (e.g., 12 km in EURO‐CORDEX, https://www.euro-cordex.net, or CORDEX‐CORE, Sørland et al., 2021). This, however, results in RCMs being used in the so‐called gray zone of convection, that is, in a grid‐spacing range of about 4–20 km.…”

Dynamical Projections of the Mean and Extreme Wave Climate in the Bohai Sea, Yellow Sea and East China Sea

“…This is because of the limited availability of high-resolution wind forcings during the conduction of the wave simulations. With the release of more high-resolution RCM datasets through the Coordinated Regional Climate Downscaling Experiment (Sørland et al, 2021), ensemble of high-resolution wave projections are in demand for the Chinese marginal seas. Furthermore, it is also interesting to investigate the capacity of these high-resolution RCMs in simulating tropical cyclones and in driving cyclone-related extreme waves.…”