The Impact of Using G3D-UW Cumulus Scheme on NU-WRF Soil Moisture-Precipitation Feedback During a Drought Evolution in Central US

Abstract:

Cumulus parameterization is an important factor affecting model precipitation forecast in coupled land-atmosphere simulations. Many studies have analyzed the sensitivity of cumulus parameterization in different models, but the performance of cumulus scheme varies with location, season, and initial conditions (e.g. dry or wet soil). Previous studies have showed preference of positive or negative soil moisture-precipitation (SM-P) relationship in coarse resolution model with parameterized convection in different regions. However, it is still not well understood the impact of cumulus scheme in SM-P process. Our previous study found a suppression of precipitation while turning off the cumulus scheme in a 4 km NU-WRF simulation in central US compared with using G3D-UW cumulus scheme. Therefore, the aim of this study is to understand how G3D-UW scheme would impact the SM-P feedback in NU-WRF, using a case study of 2018 drought in Central US. Two NU-WRF model simulations with and without G3D-UW scheme at 4 km resolution during May to October in 2018 will be analyzed. Several key variables (e.g. soil moisture, sensible/latent heat flux, boundary layer height, precipitation) representing different processes in SM-P feedback will be analyzed at different stages of drought, both in time and space. This will provide a means for quantifying the impact of cumulus scheme on the development, persistence, and recovery of drought. It also helps to understand the different mode or preference of triggering/suppressing precipitation with and without use of G3D-UW scheme in SM-P feedback, as well as the advantage and disadvantage of their application in NU-WRF for future predictions.