East Asia and Western Pacific METEOROLOGY AND CLIMATE

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west of the maximum cloud cover region.
The zonal winds are out of phase at
the upper and lower levels.
On the basis of the preceding discussion, it is our view that the 30-50
day oscillation in the equatorial atmosphere is not produced by the Kelvin
wave, but is primarily caused by the cloud wave.
In the present quasidiabatic
geostrophic model, the Kelvin wave is filtered out.
In the present
quasi-dialictic geotrophic model, the Kelvin wave is filtered out.
This is
similar to the case where the gravity wave is removed from the quasi-geostrophic
model in the midlatitudes.
From the traditional viewpoint of the dynamics of the midlatitudes, the
motion systems play the dominant role, whereas the formation of clouds is
subject to the motion systems.
However, from the standpoint of the cloud wave
for the tropical low frequency motion, the role of cloud systems and atmospheric
motions is reversed.
The cloud system plays the leading role, while
the motion systems are secondary and are determined by the cloud systems
through the cloud-radiative heating.
References
Anthes, R. A., 1977: A cumulus parameterization scheme utilizing a onedimensional
cloud model. Hon. Wea. Rev., 105, 270-286.
Chang, C. P., and H. Lim, 1988: Kelvin wave-CISK: A possible mechanism for
the 30-50 day oscillations. J. 'Atznos. Sci., 45, , 1709-1720.
Charney, J, G., 1963: A note on large scale motions in the tropics, J.
Atmos. Sci., 20, 607-609.
Gill, A. E. , 1980: Some simple solutions for heat induced tropical circulation.
Quart. J. Roy. Meteor. Soc., 106, 447-462.
Gray, W. M., E. Ruprecht, and R. Phelps, 1975: Relative humidity in tropical
weather systems. Mon. Wea. Rev. 103, 685-690.