Visualization of the missing role of hydrothermal interactions in a Japanese megalopolis for a win–win solution

The urban heat island effect has become a serious environmental problem with the expansion of cities and industrial areas. Prohibition of the use of groundwater has caused a further serious problem such as floating of subways, stations and buildings through an imbalance of the hydrologic cycle in a Japanese megalopolis. Most of the previous research has evaluated separately hydrologic and thermal cycles in atmospheric, land and water areas because of the complexity in this feedback mechanism. In this study, the author used the process-based National Integrated Catchment-based Eco-hydrology (NICE) model, which includes surface–unsaturated–saturated water processes coupled with the urban canopy and regional atmospheric models, to simulate the effect of urban geometry and anthropogenic exhaustion on the hydrothermal changes in the atmospheric/land areas of the Japanese megalopolis. The simulation was conducted with multi-scale in horizontal regional–urban-point levels and in vertical atmosphere–surface–unsaturated–saturated layers, and projected the effect of water resources use to ameliorate the heat island and its impact on the hydrologic change in the catchment. Finally, the author presented the procedure to visualize the missing role of hydrothermal interactions in atmospheric, land and water areas, which would be effective to recover a sound hydrologic cycle and to create thermally pleasing environments in an eco-conscious megalopolis.