Bridging Scales and Processes: A Land Surface Model Framework for the Urban Thermal Environment

More than half of the world’s population currently lives in cities, and the urban population is expected to reach two-thirds of the total population by 2050. As the IPCC report pointed out, the growing urban population faces heightened climate-related risks, including sea-level rise, thermal stress, tropical cyclones, heavy rainfall, etc. Of these, extreme heat stands out as one of the most important and serious urban meteorological hazards. A well-documented example is the urban heat island (UHI), which could be amplified by heatwaves (HW). However, investigating these complex interactions is often hindered by the lack of high-quality, high-resolution climate information. While regional climate models are commonly used to downscale GCMs, their heavy computational demands limit their applicability for multi-scenario urban studies. In this study, we proposed a new approach using offline land surface models to downscale reanalysis data and acquire 2m air temperature and surface temperature. Using HRLDAS/Noah-MP as an example, this accounts for diverse sub-components—such as vegetation, impervious surfaces, and anthropogenic heat—through a sub-grid tiling scheme. By explicitly simulating the energy and water exchanges within urban and natural tiles, our approach effectively captures the fine-grained thermal heterogeneity of the city. To further enhance the physical representation of urban energy and water cycles, we integrated multiple land surface models, such as SUWES and MATSIRO, into the framework. This approach provides a robust, low-cost tool for predicting near-surface thermal conditions, offering valuable insights for urban planning and the enhancement of citizen well-being in the face of a warming climate.