The ICON Single-Column Mode

Ivan Bašták Ďurán,Linda Schlemmer,Daniel Klocke,Sophia Schäfer,Noviana Dewani,Vera Maurer,Astrid Eichhorn-Müller,Annika Schomburg,Martin Köhler,Tobias Göcke,Juerg Schmidli

doi:10.3390/atmos12070906

Abstract

The single-column mode (SCM) of the ICON (ICOsahedral Nonhydrostatic) modeling framework is presented. The primary purpose of the ICON SCM is to use it as a tool for research, model evaluation and development. Thanks to the simplified geometry of the ICON SCM, various aspects of the ICON model, in particular the model physics, can be studied in a well-controlled environment. Additionally, the ICON SCM has a reduced computational cost and a low data storage demand. The ICON SCM can be utilized for idealized cases—several well-established cases are already included—or for semi-realistic cases based on analyses or model forecasts. As the case setup is defined by a single NetCDF file, new cases can be prepared easily by the modification of this file. We demonstrate the usage of the ICON SCM for different idealized cases such as shallow convection, stratocumulus clouds, and radiative transfer. Additionally, the ICON SCM is tested for a semi-realistic case together with an equivalent three-dimensional setup and the large eddy simulation mode of ICON. Such consistent comparisons across the hierarchy of ICON configurations are very helpful for model development. The ICON SCM will be implemented into the operational ICON model and will serve as an additional tool for advancing the development of the ICON model.

Highlights

Numerical weather prediction (NWP) and climate modeling are two of the most important applications in atmospheric research and operational forecasting services
While there is a strong interaction between these two processes and it is not easy to separate them in the convective boundary layer (CBL), they are traditionally parameterized in two separate schemes in NWP models: the local turbulence scheme and the non-local shallow convection scheme
In the ICON model, the local down-gradient turbulent mixing is parameterized via a turbulent kinetic energy (TKE) closure scheme [48,49] and the convection scheme for both shallow and deep convection is based on a mass-flux scheme, where the entrainment and detrainment include contributions from turbulent and organized parts [50]

Summary

Introduction

Numerical weather prediction (NWP) and climate modeling are two of the most important applications in atmospheric research and operational forecasting services. The ICON SCM was developed using the same parts of the software code as the three-dimensional ICON model with NWP physics parameterizations (model version operational since 14 April 2021 [32]) and is an integral and consistent part of the ICON framework. That the introduction of forcing and prescription of boundary conditions requires additional input for ICON SCM This information together with the initial conditions of the model are contained in a single NetCDF file, which is read at the start of the simulation. Y x (c) icnointidailtions: full levels half levels time forcings: relaxation prescribed tendencies simplified parameterization z y x boundary conditions: surface fluxes surface values Monin-Obukhov similarity theory land-surface model - TERRA

Forcing and Surface Boundary Conditions

Large Eddy Simulations

Study of the Shallow-Convection Parameterization for Three Idealized Cases

Evaluation of Clear-Sky Radiation and Improvement of the Solar Spectrum

Semi-Realistic Simulations

Conclusions