High-Resolution Land Surface Modeling of the Effect of Long-Term Urbanization on Hydrothermal Changes Over Beijing Metropolitan Area

The impacts of urbanization on terrestrial thermal and hydrological changes should be considered for sustainable development of urban environment and economy. However, previous studies mainly focused on the impacts at short time scales, which is insufficient to provide the needed information. This study augmented the high-resolution Conjunctive Surface-Subsurface Process version 2 (CSSPv2) land model with an urban canopy model that incorporates domestic wastewater recharge (DWWR) and dynamical impervious surface area (ISA) to develop a new CSSPv2_Urban model and conducted 38-year simulations over the Beijing metropolitan area at 1 km resolution to quantify the urbanization impacts. Compared with CSSPv2, CSSPv2_Urban decreases the root-mean-square errors in surface latent/sensible heat fluxes, near-surface air temperature and land surface temperature by 15%-66%, increases Kling-Gupta efficiency for streamflow by 27%-34%, and reproduces the observed long-term trends of land surface temperature and streamflow. It also reduces the corresponding errors in the modern reanalysis products by up to 70%. The model sensitivity analyses showed that the urbanization over Beijing area contributed to 31% of the surface warming during 1979-2017 and kept the warming trend over the new development zone during 2000-2013 when global warming slowed down. Although the large fraction of ISA in the city center increased streamflow by generating more surface runoff, 39%-62% of the increasing trend of streamflow was caused by the increased DWWR. Our study highlights the importance of the urban heat island effect from a climatological perspective and suggests that the influences of urbanization on streamflow may be underestimated if ignoring DWWR.

Automated summary

This study quantified the urbanization impacts on terrestrial thermal and hydrological changes in the Beijing metropolitan area using a new CSSPv2_Urban model. The results showed that urbanization contributed significantly to surface warming and streamflow trends, highlighting the importance of considering DWWR in urbanization studies.