East Asia and Western Pacific METEOROLOGY AND CLIMATE

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This implies that the large-scale clouds move eastward with a zonal speed of
about 4 m/s.
In each computational step, two associated processes are
involved.
One is the movement of the large-scale clouds caused by the
equatorial zonal current and the cloud-radiative heating associated with the
moving clouds.
The other is concerned with the new diabatic-geostrophic
balance caused by the cloud-radiative heating that produces the equatorial
zonal current.
The physical essential of the 30-50 day oscillation is a
result of the interactions between the preceding two processes.
If no other
process is considered, the large-scale clouds and quasi-balanced atmospheric
circulation caused by the cloud radiative heating will produce eastward
motions with a speed of about 4 m/s.
If the half wavelength of the largescale
clouds is about 7000 km, the period of the oscillation is 2ir/kc - 40
days.
We propose that this is the basic mechanism for the 30-50 day oscillation
in the equatorial atmosphere.
We shall refer to the preceding behavior of large-scale clouds as the
cloud wave.
The movement and development of the cloud wave are described by
the quasi-diabatic geostrophic model.
In the abow discussion, the cloud wave
has a speed of about 4 m/s.
This wave can be expressed not only in the cloud
field, but has its components in the temperature and wind fields, which can
influence the entire globe.
The upper tropospheric divergence and low-level
convergence occur in the maximum cloud cover region of the cloud wave.
In
addition, Walker and anti-Walker circulation are developed to the east and