Envelope solitary Rossby waves and modulational instabilities of uniform Rossby wave trains in two space dimensions
✍ Scribed by Dehai Luo
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 846 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0165-2125
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✦ Synopsis
Envelope solitary Rossby waves and modulational instability of a uniform Rossby wave train in two space dimensions are investigated. It is found that the condition for an envelope solitary Rossby wave to exist is [(3m2 -k2) cos2 f3 + (5m2 + k2) sin2 8]/[3m2(m2 -2k2) -k4] > 0, in which k and m are the zonal and meridional wave numbers, respectively, and 0 is a fixed angle of orientation representing the modulation direction in two space dimensions. Moreover, under a moderate condition the envelope solitary Rossby wave possesses quasi-stationary dipole structure that can tilt horizontally either westward or eastward due to the change of modulation direction, which resembles observed vortex pair blocking. If there is a set of infinitesimal sideband perturbations imposing on a uniform Rossby wave train, then the condition for instability to occur is 0 < [I.(pk)2 + Q(qw~)~]h -c 26b$ where bo is the amplitude of the uniform Rossby wave train, and the restrictions that p < 1 and 4 < 1 are required. A noteworthy property is that the instability region of p will become narrower if q increases in the small value limit. On thB other hand, it will become wider if the latitude increases for a fixed q.