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Hadley circulations and large scale motions of moist convection in the two dimensional numerical model
As a tool for understanding the meridional circulation of the atmosphere, a
two-dimensional ( latitude -- height ) numerical model is used to clarify the
relationship between the Hadley circulation and large-scale motions associated
with moist convection. The model is based on the primitive equations including
the moist process, and two kinds of coordinates are used: the spherical
coordinate and the Cartesian coordinate with a uniform rotation. The surface
temperature is externally fixed and the troposphere is cooled by the radiation;
unstable stratification generates large-scale convective motions.
Dependencies on the surface temperature difference from north to south Delta
T_s are investigated. The numerical results show that a systematic multi-cell
structure exists in every experiment. If the surface temperature is constant
(Delta T_s = 0 ), convective motions are organized in the scale of the Rossby
deformation radius and their precipitation patterns have a periodicity of the
advective time tau_D. As Delta T_s becomes larger, the organized convective
system tends to propagate toward warmer regions. The convective cells
calculated in the Cartesian coordinate model is very similar to those of the
mid-latitudes in the spherical coordinate model. In particular, the Hadley cell
can be regarded as the limit of the convective cells in the equatorial
latitudes.Comment: Submitted to J. Meteor. Soc. Japan. 36 pages for text and 16 pages
for figures. Only LaTeX source files for the text are included in a
tar-gzipped file. Full paper including postscript figures is requested from
the author (2.3 MB). Japanese version is also available from the autho
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