Understanding the Impact of Soil Moisture on Precipitation Under Different Climate and Meteorological Conditions: A Numerical Sensitivity Study Over the CONUS

• Published in: Journal of geophysical research. Atmospheres 2021-12, Vol.126 (23), p.n/a
• Main Authors: Koukoula, M., Schwartz, C. S., Nikolopoulos, E. I., Anagnostou, E. N.
• Format: Article
• Language: English
• Subjects: Agriculture; Atmosphere; Atmospheric research; Boundary conditions; Climate; Data assimilation; Data collection; Enthalpy; Evapotranspiration; Geophysics; Heat flux; Heat transfer; Kalman filters; land surface‐atmosphere interaction; Meteorological conditions; numerical weather prediction; Precipitation; precipitation forecast; Precipitation forecasting; Sensible heat; Simulation; Soil; Soil investigations; Soil moisture; Soil temperature; Spatial distribution; Storms; Water resources; Water resources management; Weather forecasting
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2021JD035096

Accurate quantitative precipitation forecasts are essential for water resources management, agriculture, and other applications. Soil moisture is among the most important boundary conditions affecting the overlying atmosphere. It can affect precipitation either directly via evapotranspiration, affecting the moisture supply to the atmosphere, or indirectly, changing sensible heat fluxes, which can affect the structure of storms and their associated distributions of precipitation. In this study we investigate the impact of soil moisture uncertainty on simulated precipitation over the conterminous United States (CONUS) with the Weather Research and Forecasting model. We selected two 30‐day periods to conduct simulation scenarios with 3‐km horizontal grid spacing over the CONUS, where the different simulations were identical except for their initial soil moisture and temperature states which were derived from three different products: Global Forecast System analyses, the National Center for Atmospheric Research (NCAR) continuously cycling ensemble Kalman filter (EnKF) data assimilation system, and the North American Land Data Assimilation System (NLDAS‐2). Results indicate different characteristics of the soil moisture–precipitation relationship during the cold and warm periods and under different climate and meteorological conditions. Better representation of initial soil moisture does not consistently provide an improvement in the simulation of precipitation. Our results suggest that soil moisture affects both the magnitude and spatial distribution of precipitation. The impact of soil moisture on precipitation is more pronounced under drier soil and strong thermal and weak synoptic forcing, while in areas with complex terrain the soil moisture‐precipitation coupling becomes weaker. Key Points Initial soil moisture affects the magnitude and spatial distribution of the simulated precipitation Better representation of initial soil moisture does not consistently provide an improvement in the simulation of precipitation The soil moisture‐precipitation feedback varies under different climate and meteorological conditions