developments towards a seamless prediction in JMA global ensemble
11 am May 20 in Room 2155
In Japan Meteorological Agency (JMA), there are ongoing developments
towards unifying existing three operational global ensemble prediction
systems (EPS), i.e. Typhoon EPS, One-week EPS and One-month EPS into
one global EPS. This new global EPS will cover the prediction of
phenomena with various timescales from short-range to sub-seasonal.
Among these developments, two topics will be mainly discussed in this
talk. First topic will be the introduction of perturbations on Sea
Surface Temperature (SST) as boundary conditions of the atmospheric
model. The current operational EPS in JMA prescribes a common SST to
all members which is derived as persistent anomaly from climatology.
This could be a significant source of underdispersiveness in the
ensemble forecasts. Statistically consistent way to generate
perturbations on SST will be proposed and tested, with promising
results leading to better spread-skill relations especially for
lower-tropospheric fields in the Tropics and summer extra-tropics.
Second topic will be the use of the Ensemble Kalman Filter (EnKF) for
the generation of the initial perturbations. Current Typhoon EPS and
One-week EPS use Singular Vectors (SVs) as the initial perturbations.
After reviewing the characteristics of the EnKF perturbations, combined
use of SVs and EnKF perturbations is proposed. Using the combination of
the EnKF perturbations with SVs leads to improve the accuracy of
short-range ensemble forecast than using only SVs, indicating that the
EnKF perturbations approximate analysis error covariance better than