ICON in Climate Limited-area Mode (ICON release version 2.6.1): a new regional climate model

Abstract

Abstract. For the first time, the Limited-Area Mode of the new ICON (Icosahedral Nonhydrostatic) weather and climate model has been used for a continuous long-term regional climate simulation over Europe. Built upon the Limited-Area Mode of ICON (ICON-LAM), ICON-CLM (ICON in Climate Limited-area Mode, hereafter ICON-CLM, available in ICON release version 2.6.1) is an adaptation for climate applications. A first version of ICON-CLM is now available and has already been integrated into a starter package (ICON-CLM_SP_beta1). The starter package provides users with a technical infrastructure that facilitates long-term simulations as well as model evaluation and test routines. ICON-CLM and ICON-CLM_SP were successfully installed and tested on two different computing systems. Tests with different domain decompositions showed bit-identical results, and no systematic outstanding differences were found in the results with different model time steps. ICON-CLM was also able to reproduce the large-scale atmospheric information from the global driving model. Comparison was done between ICON-CLM and the COnsortium for Small-scale MOdeling (COSMO)-CLM (the recommended model configuration by the CLM-Community) performance. For that, an evaluation run of ICON-CLM with ERA-Interim boundary conditions was carried out with the setup similar to the COSMO-CLM recommended optimal setup. ICON-CLM results showed biases in the same range as those of COSMO-CLM for all evaluated surface variables. While this COSMO-CLM simulation was carried out with the latest model version which has been developed and was carefully tuned for climate simulations on the European domain, ICON-CLM was not tuned yet. Nevertheless, ICON-CLM showed a better performance for air temperature and its daily extremes, and slightly better performance for total cloud cover. For precipitation and mean sea level pressure, COSMO-CLM was closer to observations than ICON-CLM. However, as ICON-CLM is still in the early stage of development, there is still much room for improvement.

Systematic Calibration of a Convection‐Resolving Model: Application Over Tropical Atlantic

“…It is thus attractive to consider a combined GCM/RCM calibration framework, that considers both approaches. Indeed, there is an increasing number of GCMs that are available in both limited‐area and global configurations, such as the ICON model (Pham et al., 2021) or the Unified Model (Bush et al., 2020). With such models, it is feasible to combine RCM‐style calibrations in subdomains.…”

Convection‐Permitting ICON‐LAM Simulations for Renewable Energy Potential Estimates Over Southern Africa

“…ICON‐NWP is used for operational global and regional forecasts by the DWD. ICON‐CLM is a recently realized mode (Pham et al., 2021) built upon ICON‐NWP in a limited‐area mode (ICON‐LAM) and facilitates a suite of technical infrastructures for regional climate applications. Here, we make use of the ICON model release version 2.6.4 (so‐called “common release” as of 2021‐09‐29) ICON‐NWP in limited area mode (ICON‐LAM).…”

COSMO-CLM regional climate simulations in the Coordinated Regional Climate Downscaling Experiment (CORDEX) framework: a review

“…Alternative parameterizations can be employed (e.g., the parameterization of convection by Bechtold et al, 2008 or land-surface models such as VEG3D or the Community Land Model; Will et al, 2017). The model versions used for CORDEX simulations are COSMO-CLM4-8-17 (Panitz et al, 2014;Keuler et al, 2016;Di Virgilio et al, 2019;Hirsch et al, 2019), multiple versions of COSMO-CLM5 (Sørland et al, 2018;Li et al, 2018), and the accelerated version COSMO-crCLIM (Vautard et al, 2020;Pothapakula et al, 2020). The following sections give short descriptions of the different versions, their main model developments, and new options for different configurations.…”

“…Whether an RCM adds value to the driving GCM data is one of the main motivations to perform dynamical downscaling (Rummukainen, 2016). Investigating whether RCM results add value to the driving GCMs should be done when comparing the downscaled results with the forcing data, and an assessment of the GCMs should also be done to determine whether the GCM has a realistic representation of the largescale atmosphere and ocean patterns (e.g., Pothapakula et al, 2020). An RCM inherits its large-scale circulation from the driving data, and any missing information from the boundary conditions is difficult to regenerate by the RCM within the simulation domain (Diaconescu and Laprise, 2013;Hall, 2014;Leps et al, 2019).…”

“…However, if a substantial adjustment is done in the model configuration (such as coupling to a different land model as done for AUS-44), the model results differ more. An RCM modeler can do a lot when it comes to improving the model performance, but if there is information missing in the large-scale GCM forcing on the RCM boundaries, it should not be expected that the RCMs can improve on that (Hall, 2014;Pothapakula et al, 2020;Rana et al, 2020). Thus, a coordinated and goaloriented strategy within CORDEX is needed for selection of the GCM data.…”