Investigating the impacts of anthropogenic heat over East China with a global variable-resolution model

Anthropogenic heat (AH) is an important urban forcing factor, with its impacts span local, regional, and larger-scale atmospheric processes. However, its multiscale effects are difficult to quantify using conventional global and regional models. Here we address this challenge by applying a global variable-resolution atmospheric model, the integrated Atmospheric Model Across Scales (iAMAS), which explicitly links urban-scale processes with regional and large-scale atmospheric feedbacks within a single modeling framework. The model employs grid spacing that transitions from 50 km globally to 3 km over the East China with 3 km to resolve the anthropogenic heat effect over urban areas. Two AH parameterizations are implemented in this study: a spatially uniform AH parameterization (UniAH) and a spatially distributed gridded dataset (GrdAH), enabling an investigation of the multiscale atmospheric impacts of different AH parameterizations. At the local boundary-layer scale, both UniAH and GrdAH indicate that AH increases near-surface temperature and planetary boundary layer height, with the strongest responses occurring in winter. Nevertheless, GrdAH reproduces observed 2-m air temperature and 10-m wind speed more accurately than UniAH. At the urban scale, both parameterizations reduce the underestimation of the urban heat island and enhance vertical motion, while producing distinct precipitation responses between urban areas and their surrounding rural regions. At larger scales associated with atmospheric circulation, both UniAH and GrdAH indicate that AH redistributes momentum, partially impeding the upper-level circulation and modifying urban-scale convergence and divergence patterns. The convergent circulation downwind of the city corresponds to enhanced precipitation, demonstrating the coupled interactions across different scales. These results highlight the inherently multiscale nature of AH effects and demonstrate the methodological value of variable-resolution modeling for capturing urban forcing and its associated multiscale atmospheric feedbacks.