Since 12 January 2005, an ensemble Kalman filter (EnKF) is being used
in Canada for global atmospheric data assimilation. It provides the
initial conditions for a medium-range ensemble prediction system.
Initial EnKF analyses were not of the same quality as the higher
resolution analyses that were obtained with a 4D-Var algorithm for the
high-resolution deterministic forecast at our center.
In part this was due to the lower resolution - and correspondingly
lower computational cost - of the EnKF. In part this was due to
weaknesses of the initial EnKF algorithm.
We have modified the EnKF algorithm and are working towards a clean
comparison
with 4D-Var.
Peter Houtekamer and
Herschel Mitchell