Representation of global mega-cities and their urban heat island in CORDEX-CORE regional climate model simulations
Abstract
Cities are highly vulnerable to climate change, yet the interactions between urban and regional climate remain insufficiently understood, especially over climate changes timescales and when comparing cities globally. Therefore, this study assesses the capabilities of two CORDEX-CORE regional climate models (REMO and RegCM) in representing urban areas globally, focusing on land-surface characteristics and urban heat island (UHI) evaluation. Despite their relatively coarse resolution (~25 km), the two models can capture urban imprints of large cities. RegCM, with a single-layer urban canopy parameterization, represents the UHI, especially at night. REMO tends to underestimate nighttime UHI due to its simple bulk urban scheme. Across models, impervious surface areas are consistently underestimated, with notable geographic imbalances across the world. Going forward, regional climate model simulations for cities require both enhanced urban parameterizations and the integration of refined urban land-use data.
Data availability
CORDEX-CORE and EURO-CORDEX data for daily maximum and minimum near surface temperature, orography, and land area fraction are publicly available through ESGF (https://esgf-data.dkrz.de/search/cordex-dkrz/). Urban and impervious surface area (ISA) fractions were collected and post-processed as part of this work and have been made publicly available on Zenodo (v1.0.0, https://doi.org/10.5281/zenodo.15700266). In addition, we provide detailed summary statistics for ISA - covering all cities, reference products, and model outputs, including mean values, percentiles (P0, 5, 25, 50, 75, 90, 100), and the number of pixels exceeding ISA thresholds of 0 and 0.1—available as both GeoJSON and CSV files on Zenodo (v1, https://doi.org/10.5281/zenodo.17313478).
Code availability
The Python code for city selection, impervious surface fraction calculation and related tasks is available on GitHub (https://github.com/FPS-URB-RCC/CORDEX-CORE-WG). The Python code for the urban heat island analysis is also available on GitHub (https://github.com/FPS-URB-RCC/urclimask).
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Acknowledgements
We would like to thank the World Climate Research Programme (WCRP) and the COordinated Regional climate Downscaling EXperiment (CORDEX) for their endorsement and support to the CORDEX Flagship Pilot Study URB-RCC. We wish to thank the partners of the WCRP CORDEX FPS URB-RCC for their engagement and contributions to the initiative. M.D. is supported by the European Union’s HORIZON Research and Innovation Actions under grant agreement No 101137851, project CARMINE (Climate-Resilient Development Pathways in Metropolitan Regions of Europe, https://www.carmine-project.eu). D.R. acknowledges support from the European Union’s HORIZON project FOCAL - Efficient Exploration of Climate Data Locally—under grant agreement No.101137787. J.F. acknowledges support from the European Union’s HORIZON Research and Innovation Actions under grant agreement No 101081555, project IMPETUS4CHANGE. G.S.L. and J.F. acknowledge support from project PROTECT (PID2023-149997OA-I00), funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU. T.H. acknowledges support from the European Union’s HORIZON Research and Innovation Actions under grant agreement No 101081555, project IMPETUS4CHANGE and by the Johannes Amos Comenius Programme (OP JAC) project No. CZ.02.01.01/00/22_008/0004605, Natural and anthropogenic georisk.
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G.S.L., T.H., and P.H. initiated the study as part of the CORDEX FPS URB-RCC proposal. G.S.L., J.F., M.D., and J.D.S. developed the conceptual approach together with the rest of co-authors. M.D. conducted the land-use analysis. J.F., J.D.S., Y.Q., and G.S.L. conducted the urban heat island analysis. G.S.L., J.F., M.D., J.D.S., L.F., N.Z., R.N., K.P.C., T.H., J.Y., P.H., and J.P.P. developed the city selection approach, and G.S.L., J.F., J.D.S., L.F., N.Z., and R.N. conducted the associated analysis. J.P.P. and G.G. produced the urban fraction data from the models. G.S.L., J.F., M.D., and J.D.S. took the lead on writing the manuscript. Y.Q., L.F., N.Z., R.N., A.F.C., K.P.C., G.G., T.H., P.H., L.E.M., J.P.P., D.R., and J.Y. revised and improved the initial draft. All authors contributed to writing and revising the manuscript.
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Langendijk, G.S., Fernandez, J., Demuzere, M. et al. Representation of global mega-cities and their urban heat island in CORDEX-CORE regional climate model simulations. npj Urban Sustain (2025). https://doi.org/10.1038/s42949-025-00325-6
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DOI: https://doi.org/10.1038/s42949-025-00325-6