WRF/UCM simulations of the impacts of urban expansion and future climate change on atmospheric thermal environment in a Chinese megacity

Urban expansion and climate change can considerably influence the regional thermal environment. In this study, the effects of changes in land cover type and vegetation coverage (referred to as LU for short), gridded anthropogenic heat (AH) emission and future climate change on atmospheric thermal environment in a Chinese megacity, Hefei, are investigated by Weather Research and Forecasting (WRF)/Urban Canopy Model (UCM) model. It is found that the increase of surface sensible heat in old urban areas is contributed by AH emission, while that in new urban areas is attributed to LU change. The LU change in new urban areas can lead to the decreased latent heat flux due to the reduction of vegetation coverage and the increase of impervious land surface. The contribution of LU change to the summer UHI intensity is about 0.76 degrees C, and AH emission to that is about 0.17 degrees C. The combined effects of LU change and AH emission in old urban areas are greater than those in new urban areas, leading to changes in daily mean 2-m air temperature, 2-m relative humidity (RH), and heat index in old (new) urban areas to be 1.08 degrees C (0.75 degrees C), - 5.93% (- 4.96%), and 2.77 degrees C (1.76 degrees C), respectively. At the end of the twenty-first century, the urban air temperature under RCP 4.5 (RCP 8.5) scenario is 0.7 degrees C (3 degrees C) higher than that at present.

Automated summary

Urban expansion and climate change have significant impacts on the regional thermal environment. Changes in land cover type, vegetation coverage, and anthropogenic heat emissions all play a role in affecting surface heat flux and urban heat island intensity. The combined effects of these factors vary between old and new urban areas.