Limited studies attempted to incorporate the dynamic urban growth into the regional modeling system over intensely urbanized city agglomerations in China. The Weather Research and Forecasting (WRF version 4.2) coupled with the single-layer urban canopy model (SLUCM) simulates the long-term climate impacts of LULC change in China's two fast-growing delta regions. The physical parameterizations in the PRD and YRD are first investigated in a high-resolution (4km) downscaled modeling. Then, the sensitivity experiments and new classified urban data are tested with fine-tuned building parameters and anthropogenic heat input in the SLUCM. The second part of the paper focuses on the impact of transient urbanization on the current and future climate. The most significant response to urbanization...[ Read more ]

Limited studies attempted to incorporate the dynamic urban growth into the regional modeling system over intensely urbanized city agglomerations in China. The Weather Research and Forecasting (WRF version 4.2) coupled with the single-layer urban canopy model (SLUCM) simulates the long-term climate impacts of LULC change in China's two fast-growing delta regions. The physical parameterizations in the PRD and YRD are first investigated in a high-resolution (4km) downscaled modeling. Then, the sensitivity experiments and new classified urban data are tested with fine-tuned building parameters and anthropogenic heat input in the SLUCM. The second part of the paper focuses on the impact of transient urbanization on the current and future climate. The most significant response to urbanization impacts comes from the SSP5 in the 2030s. The climatic interactions of different LULC in the nested domains are distinct that the PRD has warming and lower relative humidity on a local urban scale. In contrast, the YRD has broader feedback on a regional scale. Also, the urban effect on diurnal temperature varied significantly based on the forms and location of urban areas. The urbanization-induced warming mainly happened at night in the newly developed urban areas in the PRD, while such warming occurs in the late afternoon in the YRD. The local warming trend induced by urban expansion has already caused heat stress in these highly populated regions. Driven by the NorESM RCP8.5 scenario and the corresponding SSP5 urban growth data, the synergic effects of urban development and global warming are further quantified. Global warming is contributing more climatic impacts than LULC change, while the urban landcover can have an amplified effect on the local climate. The PRD and the YRD will experience dangerous heat stress under the synergic effects, with the risks of extreme in YRD developed more.