Monday, 12 January 2004: 2:15 PM
A local ensemble Kalman filter for the NCEP GFS model
Room 6A
In this paper, we present the implementation of the Local Ensemble Kalman Filter
(LEKF, Ott et al. 2003 ) on the T62, 28-level version of the full operational NCEP GFS model.
We will demonstrate that the LEKF scheme is efficient in assimilating a large
number of observations, as it is well suited to a massively parallel computing
environment. Our experiments, assimilating simulated observations (obtained
by perturbing a known true state), show that, with the current version of the
code, the assimilation of 1.7 million observations takes about 10 minutes on
a 40-processor cluster of 2.8 GHz Xeon processors (a $150,000 computer).
Also, assimilating observations at a mere 3% of the model grid points provides
analyses that are as accurate as those obtained by observing the atmospheric
state at all grid points. A modest size (40-member) ensemble is sufficient to
achieve a global analysis rms error that is significantly lower than the uncertainty in the observations for all observed variables at all model levels. Preliminary results, assimilating real observations by the LEKF, will also be presented.
Supplementary URL: