The ICON Earth System Model Version 1.0

Abstract

This work documents the ICON‐Earth System Model (ICON‐ESM V1.0), the first coupled model based on the ICON (ICOsahedral Non‐hydrostatic) framework with its unstructured, icosahedral grid concept. The ICON‐A atmosphere uses a nonhydrostatic dynamical core and the ocean model ICON‐O builds on the same ICON infrastructure, but applies the Boussinesq and hydrostatic approximation and includes a sea‐ice model. The ICON‐Land module provides a new framework for the modeling of land processes and the terrestrial carbon cycle. The oceanic carbon cycle and biogeochemistry are represented by the Hamburg Ocean Carbon Cycle module. We describe the tuning and spin‐up of a base‐line version at a resolution typical for models participating in the Coupled Model Intercomparison Project (CMIP). The performance of ICON‐ESM is assessed by means of a set of standard CMIP6 simulations. Achievements are well‐balanced top‐of‐atmosphere radiation, stable key climate quantities in the control simulation, and a good representation of the historical surface temperature evolution. The model has overall biases, which are comparable to those of other CMIP models, but ICON‐ESM performs less well than its predecessor, the Max Planck Institute Earth System Model. Problematic biases are diagnosed in ICON‐ESM in the vertical cloud distribution and the mean zonal wind field. In the ocean, sub‐surface temperature and salinity biases are of concern as is a too strong seasonal cycle of the sea‐ice cover in both hemispheres. ICON‐ESM V1.0 serves as a basis for further developments that will take advantage of ICON‐specific properties such as spatially varying resolution, and configurations at very high resolution.

Air‐Sea Interactions and Water Mass Transformation During a Katabatic Storm in the Irminger Sea

“…We analyze the development of a katabatic storm in the Irminger Sea and its induced air‐sea fluxes and water mass transformation in a frontier simulation made with ICON‐ESM (ICOsahedral Nonhydrostatic—Earth System Model; Giorgetta et al., 2018; Jungclaus et al., 2022; Korn, 2017; Zängl et al., 2015), which is participating in the second phase of the DYnamics of the Atmospheric general circulation On Nonhydrostatic Domains (DYAMOND) Winter initiative (Stevens et al., 2019, and https://www.esiwace.eu/services/dyamond/winter). The model is globally coupled and was run at a horizontal resolution of 5 km, both in the nonhydrostatic atmospheric component (ICON‐A) and in the hydrostatic ocean/sea ice component (ICON‐O).…”

Seamless Integration of the Coastal Ocean in Global Marine Carbon Cycle Modeling

“…The biogeochemistry component of ICON‐O is the Hamburg Ocean Carbon Cycle model HAMOCC (Ilyina et al., 2013; Maier‐Reimer et al., 2005) in its CMIP6 version (Mauritsen et al., 2019). This version was transferred from the Earth system model MPI‐ESM to ICON‐O as the ocean component of the Earth system model ICON‐ESM (Jungclaus et al., 2022). Marine biology dynamics is represented by a NPZD‐type approach (Six & Maier‐Reimer, 1996).…”

High-Performance Computing in Meteorology under a Context of an Era of Graphical Processing Units

“…Deutscher Wetterdienst (DWD) is responsible for meeting the meteorological requirements arising from all areas of the economy and society in Germany. The operational weather model, ICON [13], has an icosahedral grid system to avoid the so-called pole problem, which produces too small grids in polar regions to set long time steps in numerical integrations due to the Courant−Friedrichs−Lewy Condition [14].…”