Sensitivity study of T2m and precipitation forecasts to soil
moisture initial condition using NCEP WRF ensemble system
Jun Du and George Gayno
EMC/NCEP/NOAA
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 http://www.emc.ncep.noaa.gov/mmb/SREF/SREF.html