Abstract:

Karst hydrology provides a unique set of surface and subsurface hydrological components that affect soilmoisture variability. Over karst topography, surface moisture moves rapidly 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 snowmelt over karst can lead to surface flooding. Moreover, regionsdominated by karst may exhibit either drier or wetter soils when compared to nonkarst landscape. However,because of the lack of both observational soil moisture datasets to initialize simulations and regional landsurface models (LSMs) that include explicit karst hydrological processes, the impact of karst on atmosphericprocesses is not fully understood. Therefore, the purpose of this study was to investigate the importance ofkarst hydrology on planetary boundary layer (PBL) atmosphere using the Weather Research and ForecastingModel (WRF). This research is a first attempt to identify the impacts of karst on PBL. To model the influenceof karst hydrology on atmospheric processes, soil moisture was modified systematically over the WesternKentucky Pennyroyal Karst (WKYPK) region to produce an ensemble of dry and wet anomaly experiments.Simulations were conducted for both frontal- and nonfrontal-based convection. For the dry ensemble, cloudcover was both diminished downwind of karst because of reduced atmospheric moisture and enhanced slightlyupwind as moist air moved into a region of increased convection compared to control simulations (CTRL).Moreover, sensible (latent) heat flux and PBL heights were increased (decreased) compared to CTRL. Inaddition, the wet ensemble experiments reduced PBL heights and sensible heat flux and increased cloud coverover karst compared to CTRL. Other changes were noted in equivalent potential temperature (ue) andvertical motions and development of new mesoscale circulation cells with alterations in soil moisture overWKYPK. Finally, the location of simulated rainfall patterns were altered by both dry and wet ensembles withthe greatest sensitivity to simulated rainfall occurring during weakly forced or nonfrontal cases. Simulatedrainfall for the dry ensemble was more similar to the North American Regional Reanalysis (NARR) thanCTRL for the nonfrontal case. Furthermore, the initial state of the atmosphere and convective triggers werefound to either enhance or diminish simulated atmospheric responses