Sensitivity study of T2m and precipitation forecasts to soil moisture initial condition using NCEP WRF ensemble system

Jun Du and George Gayno

NCEP Short-Range Ensemble Forecasting (SREF) system has been running in operation since 2001. It's noticed that ensemble spread particularly in precipitation and near-surface variables such as 2m temperature are underdispersive especially in warm seasons. Early research results suggested that perturbing soil moisture in land surface model (LSM) might increase ensemble spread in summer rainfall forecasts. To test if it's also the case in operational setting, a series of sensitivity tests of precipitation and near-surface variables to soil moisture initial conditions are performed using the NCEP operational WRF ensemble system for both warm and cold season cases. This talk will present the results from those preliminary sensitivity studies including the variation of sensitivity with the structure and size of perturbations as well as with seasons. It's planned to add perturbations to LSM to further increase diversity of the NCEP SREF system although it is a quite challenging task how to design a simple and effective perturbation generating scheme in LSM for an operational ensemble system. For NCEP regional ensemble system, you can go to