The influence of karst hydrology on local planetary boundary layer

Karst hydrology provides a unique set of surface and subsurface hydrological components that affect volumetric soil moisture variability. Over karst topography, surface moisture is rapidly directed below ground via sink holes, vertical shafts, and sinking streams, reducing surface runoff and moisture infiltration into the soil. In addition, subsurface cave blockage or rapid snow melt over karst can lead to surface flooding. Moreover, regions underlain by karst may exhibit either dryer or moister soils when compared to nonkarst topography. However, due to the lack of both dense observational volumetric soil moisture datasets to initialize simulations with and regional land surface models (LSM) that include karst hydrological processes, the impact of karst on atmospheric processes is marginalized. Therefore, the purpose of this study was to investigate the importance of karst hydrology on near-surface atmospheric processes using numerical modeling techniques. This research is a first attempt to identify the importance of localized hydrological processes, such as karst, in numerical weather prediction models. To model the influence of karst hydrology on atmospheric processes, volumetric soil moisture was varied systematically over Western Kentucky Pennyroyal Karst to produce an ensemble of dry and wet anomaly experiments. Simulations were conducted for both frontal and non-frontal based convection. For the dry ensemble, cloud cover was both diminished downwind of karst due to reduced atmospheric moisture and enhanced slightly upwind as moist air moved into a region of increased convection compared to control (CTRL). In addition, the wet ensemble experiment reduced PBL heights and increased cloud cover over karst compared to CTRL. Simulated rainfall patterns were altered by both dry and wet ensembles, but accumulated precipitation remained unchanged. Simulated response to soil moisture variability was strongest for non-frontal than frontal based convection. Furthermore, the initial state of the atmosphere and convective triggers were found to either enhance or diminish simulated atmospheric responses to karst.