East Asia and Western Pacific METEOROLOGY AND CLIMATE

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where r 4j is the correlation coefficient, Ey the Euclidean distance between
two anomaly fields, S i Sj the mean squared deviations of the two fields,
respectively, S = S. + S .: m the number of mesh points. The results show
m i j
that a quasi—semiannual rhythm exists significantly, i.e. the anomalous
fields between two different years are analogous in a starting month, the
similarity will rapidly become poorer in time, but after about six months, it
will become a little analogous again. It appears that a quasi-semiannual
rhythm phenomenon does exist in the evolution of monthly averaged circulation
anomalies and SST anomalies. Further research on this area will
greatly encouraged us to realize climate anomalies of a seasonal scale and
design numerical climate forecasting models correctly.
3. The Mechanism Of Analogous Rhythm
Some research has been done on the comprehensive interpretation of the
physical mechanism of rhythm. Marchuk(1979) (6) tried to explain the
rhythm with air—sea interaction. In a further study, Musealyan
(1980) (7) suggested that, during the summer half year, solar radiation is
obsorbed and stored in the deep layer of the sea, which may be called a
"memory 77 process; and during the winter half year, the stored energy is
transfered to the air through different processes and then propogated
downstream with the flow. In this way, he explained the formation of temporal
teleconnection between time-mean summer cloud cover over the
North Atlantic and the winter temperature in European parts of Russia.
Zhao and Wang (1982) (15) found that the rhythm indices depend closely
on geographical regions and the most significant indices appear in oceans.
This is another evidence of the relation between rhythm and air-sea
interaction.
In a study of long—term weather processes on air—sea interaction, Zang
and Wang (1983) (14) pointed out that there is. an obvious rhythmic relation
between summer SST and winter SST in the west drift region. They explained
that, during summer the ocean active layer is warm in the up-layer
and cool in the down-layer; solar energy and heat energy transferred by
atmospheric turbulent exchange are absorbed by the ocean, increasing the
temperature in the surface layer; in winter, ocean discharges the energy
stored in summer and the thermodynamic structure of the ocean active layer
becomes an isothermal one. Therefore, the influence of summer SST
anomalies on the air can be detected only in winter.