Journal of the Meteorological Society of Japan. Ser. II
Online ISSN : 2186-9057
Print ISSN : 0026-1165
ISSN-L : 0026-1165
On the Dynamics of Easterly Waves, Monsoon Depressions, and Tropical Depression Type Disturbances
Adam H. SobelTakeshi Horinouchi
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2000 Volume 78 Issue 2 Pages 167-173


The authors argue that certain aspects of the rotational, synoptic-scale disturbances of the wind field that are observed in ITCZ or monsoon trough regions can be understood by considering the linear response of a dry, initially resting atmosphere to a pulse of heating whose amplitude and spatial and temporal scales are characteristic of a large mesoscale convective system. The key points are that short Rossby waves have small intrinsic group and phase velocities, and that a heating pulse projects much more energy on the Rossby modes if it is located slightly off rather than on the equator. It follows that synoptic-scale Rossby waves, with characteristics broadly similar to those of observed disturbances, should be present in off-equatorial regions of persistent deep convection, since large mesoscale convective systems tend to develop in such regions.

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