The Effects of Urbanization on China's Future Climate based on Dynamically Downscaled Projections

Abstract:

Human-induced land cover changes such as urbanization play an important role in regional-scale climate change, due to the altered land-atmosphere interactions in urban areas. We investigate the impacts of projected urbanization in China on future climate. Using the Weather Research and Forecasting (WRF) model, we downscale Community Earth System Model (CESM) projections based on Representative Concentration Pathways (RCP) 4.5. We find decreased latent and increased sensible heat fluxes over the urban areas by 2050, leading to higher surface temperatures and lower humidity. The projections further reveal that urbanization produces strong warming, up to 1.9°C at regional and local/urban scales, which is of similar magnitude to the greenhouse gas forcing under the RCP 4.5 scenario. At night and during summer, greater urban warming effects are projected, which can be attributed to the high heat capacity of built-up areas. Precipitation responses are more complex, and the impacts of urbanization show varying consequences, primarily in summer. Both precipitation increases and decreases are projected depending on spatial scale, and related to both local moisture deficits and large-scale circulation changes. As this region is also greatly impacted by the monsoon, we find that urbanization will strengthen the East Asian summer monsoon in southern China, and slightly weaken the winter monsoon in eastern China. These results suggest that for the most realistic and complete depiction of future climate, urbanization should be included in model projections