| 13 Jan 2026
From Single Storms to Global Waves: A Global 2.5 km ICON Simulation of Weather and Climate
Abstract. Global kilometer-scale (km-scale) weather and climate models offer new opportunities to unify numerical weather prediction (NWP) and climate modeling by explicitly simulating convection and mesoscale circulations globally within a single modeling framework. We present results from the first multi-year (April 2020–March 2024) global atmosphere-land simulation using the GPU-refactored ICON model at a 2.5 km horizontal grid spacing and 120 vertical levels. The simulation uses NWP physics and observed sea-surface temperatures. We assess its performance against satellite, reanalysis, and in-situ observations using standard statistics and the MOAAP feature-tracking framework to evaluate a wide spectrum of atmospheric phenomena. ICON reproduces global temperature and precipitation patterns, including a realistic single Intertropical Convergence Zone and physically consistent diurnal precipitation cycles. However, ICON exhibits continental warm and dry biases during the warm season, linked to an overestimation of incoming solar radiation and excessive surface sensible heat fluxes. The model realistically captures the intensity and frequency of hourly precipitation and near-surface winds, as well as the structure and occurrence of tropical cyclones. Mesoscale convective systems (MCSs) exhibit realistic spatial initiation patterns, but their frequency is underestimated over oceans and overestimated over tropical land. Long-lived MCSs are too infrequent and small, while excess rainfall from shallow and mid-level clouds suggests overactive warm-cloud microphysics. These biases likely stem in part from an underrepresentation of convectively coupled equatorial waves. Our results demonstrate the feasibility and scientific value of multi-year global convection-permitting simulations for exploring the weather–climate system and local-scale extreme events, while identifying key directions for future model development.
Dear authors,
Unfortunately, after checking your manuscript, it has come to our attention that it does not comply with our "Code and Data Policy".
https://www.geoscientific-model-development.net/policies/code_and_data_policy.html
First, in the Code and Data Availability section of your manuscript you do not provide a repository for the version of ICON that you use in your work. Also, you state "The global 2.5 km ICON simulation... will be made publicly available through the DYAMOND-III intercomparison archive upon completion of the coordinated data release. Until then, access can be provided by the corresponding author upon reasonable request.", which is neither acceptable.
Finally, for the other datasets used to produce your work, you provide links to the generic web pages that contain them, and what is needed is that you cite specific repositories that comply with the policies of the journal and contain the data you have used.
If we have missed a published policy which does in fact address this matter satisfactorily, please post a response linking to it. If you have any questions about this issue, please post them in a reply.
The GMD review process depends on reviewers and community commentators being able to access, during the discussion phase, the code and data on which a manuscript depends. Please, therefore, publish your code and data in one of the appropriate repositories and reply to this comment with the relevant information (link and a permanent identifier for it (e.g. DOI)) as soon as possible. We cannot have manuscripts under discussion that do not comply with our policy.
The 'Code and Data Availability’ section must also be modified to cite the new repository locations, and corresponding references added to the bibliography.
I must note that if you do not fix this problem, we cannot continue with the peer-review process or accept your manuscript for publication in GMD.
Juan A. Añel
Geosci. Model Dev. Executive Editor