H199-0015
Investigating the impact of soil moisture on precipitation and runoff generation over the contiguous United States.

Wednesday, 16 December 2020
Poster
Marika Koukoula, University of Connecticut, Civil and Environmental Engineering, Groton, CT, United States, Efthymios I Nikolopoulos, Florida Institute of Technology, Mechanical and Civil Engineering, Melbourne, United States, Humberto J Vergara, Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK, United States, Jonathan J Gourley, National Severe Storms Lab, Oklahoma City, OK, United States and Emmanouil Anagnostou, University of Connecticut, Civil and Environmental Engineering, Storrs, CT, United States
Abstract:
Soil moisture is an important hydrological state variable playing a crucial role in land atmosphere interactions. Soil moisture affects precipitation directly via evapotranspiration affecting the moisture supply to the atmosphere. It can also indirectly affect the large-scale atmospheric circulation patterns as well as the microphysical structure of storms and their associated distributions of precipitation. Additionally, soil moisture affects infiltration rates and thus has an important control on rainfall-to-runoff transformation process. Consequently, understanding the role of soil moisture in land-atmosphere interactions across different climate conditions and basin characteristics is fundamental to climate research, atmospheric and hydrological modeling, and extreme events monitoring.

In this study we investigate the effects of soil moisture on runoff generation over the conterminous United States (CONUS). We selected two 30-day periods (a cold and a warm season period) to conduct sensitivity simulations with the Weather Research and Forecasting (WRF) model at 3-km horizontal grid spacing over the CONUS, using initial soil moisture and temperature conditions derived from three different products: Global Forecast System (GFS) analyses, the NCAR continuously cycling ensemble Kalman filter Data Assimilation system, and the North American Land Data Assimilation System (NLDAS). Subsequently, we used precipitation and potential evapotranspiration derived from the atmospheric simulations as forcing for the Ensemble Framework for Flash Flood Forecasting (EF5) modeling system to conduct distributed hydrologic simulations over the CONUS. For these simulations we updated soil moisture every 24 hours using the datasets we used for the atmospheric simulations.

Results indicate different characteristics of the soil moisture–precipitation-runoff generation relationship under different meteorological conditions and across regions. Furthermore, soil water content affects mostly the spatial distribution of precipitation rather than the total amount of rainfall. We found a higher impact of soil moisture on precipitation during summer. The overall results suggest that soil moisture affects runoff generation, however the strength of the relationship depends on the soil properties.

<< Previous Abstract | Next Abstract >>