Better

In line with WarmWorld’s overarching mission to develop key components of climate information systems, the Better module takes on its role in enabling the successful simulation of an ICON-based model at a resolution of 2.5km or lower. The module’s central target is thus a more detailed description of underlying climate physics that will allow the simulation on finer model grids. While the Faster module’s responsibility lies in ensuring a model throughput of >0.5 SYPD, the Better activity groups strive to deliver an adequate configuration of the SR-ESM ahead of development Phase 2. In this sense, the task profiles of both groups are closely intertwined and are locked into a continuous collaborative exchange.

To establish a better representation of climate physics in the Earth System, Better in particular focuses on optimizing configurations of cloud-physics, turbulent-mixing, and land-surface processes. Practically this means that Better assumes responsibility for fine-tuning these processes to best represent the vertical structure of the atmosphere,capture land-atmosphere interactions, and establish a balanced water and energy budget to support long-term applications. Transferring a close understanding of these physical processes and their interaction into the ICON-C structure is vital to achieve overall better information on future scenarios.

The second strain of Better’s work concentrates providing a robust risk assessment through enabling a quantification of uncertainties. Better will provide and support a system for shadowing, and thus assessing, ICON-based future projections – so-called Simulation ghosts, based on ECMWF’s IFS model coupled to the sophisticated and flexible ocean model FESOM develpod at AWI. In addition the Research Centre Jülich can boast extensive experience in the development of Earth System Models (ESMs) from the regional to the global scale. Together, these institutions will concert their expertise to the meet the challenges the WarmWorld project presents.

In an effort to achieve more detailed representations of atmospheric processes, the Better activity groups will build on and extend existing efforts in NextGEMS. Thus the WarmWorld project and its outputs link to and benefit from collaboration with an international network of climate modeling projects.

Project partners:

• Alfred-Wegener-Institut Helmholtz Zentrum für Polar- und Meeresforschung
• Deutsches Klimarechenzentrum
• European Centre for Medium-Range Weather Forecasts
• Forschungszentrum Jülich
• Karlsruher Institut für Technologie
• Max-Planck-Institut für Meteorologie
• Universität Hamburg
• Universität Leipzig

Integrating ParFlow with ICON-Land – Closing the water cycle from the continents to the oceans

Representing hydrological processes in large-scale climate and Earth system models is important in order to simulate the coupled water, energy, and matter cycles, and predict the distribution of water in the atmosphere, on the land, and in the subsurface. In large model frameworks, such as ICON, the hydrological model usually is part of the land surface model. For the subsurface, oftentimes, these are isolated 1D column models based on simplifying assumptions and empirical relations. Hence, 3D groundwater dynamics and the connection of surface water along river corridors is not properly represented. However, this can be expected to be crucial for better predicting the soil moisture distribution and evapotranspiration, and for better resolving continental water-energy-matter-cycle processes on the climate scale.

One goal of subproject WarmWorld Better (AG3) is to integrate ParFlow with the ICON-Land modeling framework for an improved representation of subsurface and surface hydrological processes. ParFlow simulates 3D variably saturated groundwater-surface water flow in a continuum approach including groundwater, soil water and overland flow. Integrating ParFlow with ICON-Land will allow to resolve 3D hydrodynamics along individual hillslopes in complex terrain, and convergence of groundwater and surface water interactions along river corridors. Thus, for the first time, the hydrological cycle will be consistently closed from the continents to the oceans in high-resolution global simulations.

Technically, the coupling will be realized using the YAC coupling library which is already well established within the ICON framework linking the atmosphere with the ocean. YAC allows for parallel data exchange and provides efficient interpolation methods for almost any grid. The implementation of YAC will be based on existing interfaces and software infrastructure in ParFlow that are well tested. As ParFlow is performance portable and massively parallel, the integration will facilitate the efficient use of exascale supercomputing environments.