Mapping Urban Heat Islands for Estimating City-Wide Heat Increases in Relation to Background Global Warming

Creating city-wide maps of the canopy-layer urban heat island, or the spatial variation of air temperature within the canopy layer, generally requires the use of an urban climate model. This model must be able to resolve the complex energy exchanges between the urban surface and the atmosphere as well as the detailed atmospheric physics near the city surface at a sub-kilometer resolution. As a result, significant computational resources are necessary. Simpler statistical approaches are available but often restricted to specific weather conditions (e.g. maximum nighttime urban heat island intensity). Here we use a computationally and methodologically simple approach which relates local climate zones to canopy-layer air temperature to generating maps of the urban heat increment in reference to a specific local climate zone across Singapore Island for different periods of the day, different seasons and weather conditions. By utilizing historical land cover maps alongside projections for future urban development, it is possible to estimate how this temperature increase has evolved over time and how it may change in the future. Finally, by integrating global warming projections, future canopy-layer air temperatures can be determined. Initial results suggest a present-day extra ~1.0ºC warming due to the presence of urban areas across Singapore Island considering area-weighted distribution of LCZs and all-weather daily averages. This urban-induced warming is therefore of similar magnitude to that caused by anthropogenic global warming. Following the introduction of the long-term canopy-layer air temperature observations essential to the methodology, the presentation will show how urban heat levels have changed during Singapore's rapid development over the past 60 years, alongside future projections using recent high-resolution local climate projections for this tropical area.