Development and testing of a fully-coupled subsurface-land surface-atmosphere hydrometeorological model: High-resolution application in urban terrains

To improve simulation of atmospheric-hydrological processes with shallow groundwater in urban areas, a new fully-coupled model was developed. The Weather Research and Forecasting (WRF) atmospheric model in the large-eddy-simulation (LES) mode, the Princeton Urban Canopy Model (PUCM), and the subsurface hydrological model ParFlow (PF) were linked (WRF-PUCM-PF). To evaluate the impact of coupling, model intercomparison was performed by application to a small watershed in suburban Baltimore, Maryland, USA, for scenarios of both homogeneous and heterogeneous geologic properties, using WRF-PUCM with and without the ParFlow component. Homogeneous scenarios isolated the impact of including terrestrial hydrological processes through ParFlow. In response to rain events, the homogeneous WRF-PUCM model output gained and retained a 40% greater amount of soil moisture (area-averaged) compared to the homogeneous WRF-PUCM-PF case. In heterogeneous scenarios, the WRF-PUCM model generated a 10-fold greater area-averaged soil moisture increase over the simulation period compared to the WRF-PUCM-PF case. The WRF-PUCM-PF model output, influenced by lateral hydrology and impervious surfaces, generated lower latent heat flux, resulting in half of the domain having higher land surface temperatures (2–10 °C), compared to the WRF-PUCM model. Overall, the WRF-PUCM-PF model provides a new tool to simulate urban physics and resolve finer urban microclimatic heterogeneity.