The tenth IMSC, Beijing, China, 2007 - International Meetings on ...

esults, the guidance on the determination of threshold for binary forecast is proposed for each
pattern.
Using this guidance, the heavy snow forecast in Korea is considered as a case study.
Effects of daily MOC fluctuations on long-term MOC predictability
Speaker: Jin-Song von Storch
Jin-Song von Storch
Max-Planck Institute for Meteorology
jin-song.von.storch@zmaw.de
Helmuth Haak
Max-Planck Institute for Meteorology
<strong>The</strong> first continuous assessment of the Atlantic meridional overturning circulation
(MOC), achieved within the framework of the UK Rapid Climate Change Program, indicates
strong MOC variability on timescales of about a few weeks. A large part of this variability
results from or is related to the wind stress forcing. Assume that this MOC variability is not
predictable beyond a few weeks, its presence will significantly limit the long-term MOC
predictions which owe their skill to the slow ocean dynamics. To quantify this limitation, daily
and yearly MOC time series generated by the ECHAM/MPI-OM model are used to test two null
hypothesis: one addresses the existence of the slow dynamics and the other the strength of
the variability generated by the slow dynamics relative to the low-frequency white-noise
extension of the unpredictable short-term fluctuations. <strong>The</strong> analysis is carried out for different
frequency ranges by decomposing the variances in frequency domain. It is found that the
model slow dynamics start to operate on timescales longer than two to three years and the
variance generated by the slow dynamics can only be over and above the low-frequency
white-noise extension of the unpredictable noise when considering timescales longer than 20
years. <strong>The</strong> result suggests that when predicting the MOC by initializing the ECHAM/MPI-OM
model using an ocean analysis, a long initialization time period, preferably longer than 20
years, is required to capture the state of slow dynamics at the initial time.
On the reliability of ENSO dynamical predictions
Speaker: Youmin Tang
Youmin Tang
University of Northern British Columbia, Canada
ytang@unbc.ca
Richard Kleeman
Courant Institute, New York University, USA
82