Effects of lateral groundwater flow on hydrologic extremes

Land Surface Models (LSMs), originally designed to represent the water and energy fluxes at the land-atmosphere boundary, have also evolved to represent the details of subsurface moisture processes. However, many LSMs lack more advanced physical processes, particularly lateral flow and groundwater flow. Recent literature has shown that groundwater flow can be important for the progression of convection or flash droughts in semi-arid environments, which are increasingly relevant in a changing climate. The Miguez-Macho and Fan (MMF) groundwater scheme is available as a runoff and groundwater parameterization in the Noah-MP LSM. In this work, we explore the specific impacts of simulating groundwater at continental scales during extreme events over North America. We consider water budget variables, including water and energy fluxes and surface runoff simulated by Noah-MP. The Noah-MP LSM is executed with MMF lateral flow and is compared to previous, simpler configurations of the LSM. In this study, we quantify the impact of improved representation of lateral groundwater processes on land surface fluxes and states. Additionally, we will present the impact of these improvements on the quantification and representation of hydrological extremes such as droughts. Specifically, we will examine the extent to which the onset, progression, and severity aspects of droughts are improved through the MMF scheme.