ICON-Seamless, the development of a novel Earth System Model based on ICON for time scales from weather to climate

<p>Within the project ICON-Seamless a new Earth System Model is developed for weather forecasts, seasonal and decadal climate predictions, as well as climate projections. In doing so, we use the expertise from the numerical weather prediction (NWP), which operates and maintains ICON-NWP, as well as the experience with the first ICON-Earth System Model version based on the physics of the MPI-M atmosphere model (ECHAM). The goal is to use common components for all time scales. As a first step we develop a model for seasonal and decadal predictions.</p><p>ICON-Seamless builds on the coupling of the atmosphere (ICON-NWP) and ocean (ICON-O) components via the coupling software YAC. Sea ice as a further important component is thereby included. Furthermore, to have a closed hydrological cycle and to represent the carbon and other biogeochemical cycles comprehensively, a suitable soil model based on the ICON-Land framework as well as the TERRA and JSBACH/QUINCY land models, are or will be coupled to ICON-NWP. In addition, transient external fields for aerosol, greenhouse gases, ozone and solar irradiance are implemented in ICON-NWP to be able to simulate historical time periods and scenarios of the future. In parallel, the ART modules (Aerosol and Reactive Trace gases), which allow a dynamic treatment of gases and aerosol, are adapted to the modified model physics. Intensive model evaluation supports the tuning. For future use in the field of (weather and) climate predictions, coupled data assimilation is being developed as well.</p><p>We give an overview of the current state of the development, experiments and potential areas of application.</p>