Evaluating the Representation of Cities in a Convection Permitting Climate Model over Southeast Asia

The IPCC AR6 Working Group 2 report (https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-6/) states 'evidence from urban and rural settlements is unequivocal; climate impacts are felt disproportionately in urban communities, with the most economically and socially marginalised being most affected.' However, climate information at the urban scale remains limited, as urban areas have historically been excluded from climate models, and recent attempts to incorporate them vary in complexity.

To assess the role of urban land surface description in climate projections, we conducted three convection-permitting climate model (CPM) experiments (4 km grid length) over Southeast Asia (1981-2000), covering Bangkok, Hanoi, Ho Chi Minh, and Phnom Penh. Each simulation progressively enhances land surface detail, utilizing high-fidelity datasets (WorldCover and World Settlement Footprint 3D) to refine land cover and building morphology representation. Initial findings indicate that these improvements significantly impact temperature (1-2°C), with variations by city. The CPM experiments are still running and we will present our results in full once they have completed.

High-resolution climate projections capable of resolving urban areas are rare. Our results advance understanding of how urban areas influence their climate and provide valuable insights for future urban CPM projections, with the potential to contribute to the AR7 Special Report on Climate Change and Cities.