The ICON‐ParFlow Coupling: Integrating a Continental‐Scale Hydrological Model Into a Global Atmospheric Model
Abstract
In Earth system models, three‐dimensional prognostic subsurface hydrodynamics, including groundwater flow, are currently missing at the global scale. In order to prepare Earth system models for kilometer‐scale simulations with integrated continental hydrology, the ParFlow hydrological model has been coupled to the land model of the ICON modeling framework. Global simulations of atmosphere and land were conducted with a two‐way coupling between ParFlow and the soil hydrological scheme of ICON‐Land over the pan‐European region. In this first implementation, ParFlow and ICON‐Land exchange surface moisture fluxes and soil water. The extended summer months of five consecutive years were simulated with 20 km horizontal grid spacing. The explicit treatment of surface and subsurface water in ParFlow has multiple effects. Some notable impacts are presented related to soil moisture variability and lateral redistribution of moisture. Correlations with surface latent heat flux and precipitation show regionally stronger land‐atmosphere coupling. This affects the seasonal change in soil water content in Central Europe during the summer. In addition, the lateral flow of near‐surface groundwater, which is intrinsically linked to the formation of river networks, is shown to influence the evolution of the atmosphere.