Figure 1 Nino
3.4 SST prediction skill is measured by anomaly correlation for the lead
time of 1-6 months. CFS and CMP14 are the same coupled model system with
the only difference in vertical resolution of the atmospheric component
and 28 layers, respectively. The other acronym labels are the major
statistical methods used in Climate Prediction Center for routine ENSO forecasts.
A new global coupled atmosphere-ocean forecast system model (CFS03) has
recently become operational at the National Centers for Environmental
Prediction (NCEP). The new coupled model consists of a T62L64 version of the
operational NCEP Atmospheric Global Forecast System model and the
Geophysical Fluid Dynamics Laboratory Modular Ocean Model version 3.
The atmospheric and oceanic components are coupled without any flux
of the new coupled model has been assessed and demonstrated not only
superior to the old system (see Significant Improvement below) but also for the first time in
the history the model hindcasts show comparable skill to the statistical
forecast for Nino 3.4 sea surface temperature (SST), which is considered to be a
desirable index used by forecasters to make seasonal prediction (Figure 1).
improvement mainly came along with the increase of vertical resolution from
28 layers to 64 layers. The cause and effect are under investigation.
of 64 layers, the result of which being compared with that of the
same model but with 28 layers
2 shows the vertical structure difference between
64 and 28 layers. )
Initial condition taken from GDAS and GODAS
climatology is reasonably good in the tropics and subtropics, where errors
are generally within 1K. (Figure
momentum flux and sea surface height (SSH) climatology distribution are
The model simulates
ENSO variability with realistic frequency (period of 3-5 years) and
similar amplitude to that of the observed strong events.
leading EOF modes of SSH are similar to those from oceanic analysis.
The observed feature that the EOF1 and Nino3.4 SSTs are almost in phase
and both lead EOF2 by about two to three seasons.
the observed ENSO seasonal phase-locking with the peak amplitude occurring
near the end of the year.
The ENSO events in
the simulation occur more regularly than in observations.
simulated warm events tend to start about three months earlier and persist
longer than observed.
The amplitude of the
simulated east-west gradient of SSH climatology appear to be smaller than
that of the observation analysis.
Why is the vertical resolution so critical to the CFS prediction skill improvement?
shows comparable result obtained by the coupled
ocean (ORCA) and atmosphere (ECHAM) model at T30 and 19 hybrid levels.
(Guilyardi and Delecluse 2003)
physics are the causes for the regularity of the simulated ENSO cycle, why
the simulated ENSO lasts longer than the observed?
the cause of the warm bias in the south eastern tropical Pacific?
source of the long-term trend in the surface and subsurface temperature?
sensitive the simulated ENSO is to the modelís numerics and physics?
Wang, W., S. Saha, H. Pan, S. Nadiga
and G. White, 2005: Simulation of ENSO in the new NCEP coupled forecast
system model (CFS03). Mon. Wea. Rev., 133, 1574 - 1593.