Impact of Subsurface Hydrofacies and Groundwater Configuration on Convective Initiation in a High-Resolution Coupled Hydrometeorological Model

Meteorological models, with land surface models (LSMs) as their lower boundary conditions, have vastly improved in their ability to credibly predict soil moisture redistribution. However, there is a growing body of literature suggesting that several commonly used assumptions in LSMs can corrupt the terrestrial water balance and subsequently meteorological estimates. These include a free-draining lower boundary condition, shallow soil depth, one-dimensional (vertical) subsurface flow, and limited or nonexistent groundwater or surface water routing representations. Recently developed fully-coupled, bedrock-to-atmosphere modeling platforms, which employ physically-based, distributed hydrologic models as their lower boundary conditions, have demonstrated improved surface water budget closure and improved forecasts of surface turbulent fluxes and meteorological conditions. Mesoscale convective systems are not only functions of both localized, terrain-induced features and large-scale synoptic patterns, but are also sensitive to antecedent soil moisture conditions and moisture redistribution in the subsurface. Therefore, relaxed assumptions regarding the terrestrial hydrology, such as those used in LSMs, could have considerable influence on the origin, timing and progression of convective events. This study employs a mesoscale meteorological model with full two-way coupling to a hydrologic model, in order to test the impact of relaxed lower boundary conditions on atmospheric states. Specifically, we adjust deep geologic hydraulic parameters, initial soil moisture and water table conditions, and hydrologic-atmospheric model information exchange frequency, and observe the influence on convection initiation.