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Original Research Papers

Is asymptotic non-divergence of the large-scale tropical atmosphere consistent with equatorial wave theories?

Authors:

Kevin Delayen,

Parcours “Atmosphere Ocean Continent”, UPS, Toulouse, FR
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Jun-Ichi Yano

CNRM–GAME (Météo-France, CNRS), 31057 Toulouse
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Abstract

Observations suggest that the large-scale tropical atmospheric circulations, associated with intraseasonal variabilties, are dominated more by the vorticity than the divergence. The present paper examines the consistency of the above observations with linear equatorial wave theories. Both free and forced linear waves are considered. The free equatorial waves are classified into two major categories: (1) the Rossby waves, strongly dominated by vorticity and (2) the inertial-gravity waves, relatively dominated by the divergence. Both the Kelvin and the mixed-Rossby gravity waves are intermediate of these two major categories.

In the forced case, the wave response is predominantly inertial-gravity wave-like for periods less than 5 d, thus predominantly divergent. On the other hand, for forcing with the longer periods, the wave response closely following free Rossby-wave structures, asymptotically approaches to a non-divergent state. The asymptotic tendency for nondivergence is found to be much stronger than observed. The difference is so stark that, notably, the tropical intraseasonal variability cannot be consistent with linear equatorial waves theories.

How to Cite: Delayen, K. and Yano, J.-I., 2009. Is asymptotic non-divergence of the large-scale tropical atmosphere consistent with equatorial wave theories?. Tellus A: Dynamic Meteorology and Oceanography, 61(4), pp.491–497. DOI: http://doi.org/10.1111/j.1600-0870.2009.00404.x
  Published on 01 Jan 2009
 Accepted on 20 Apr 2009            Submitted on 27 Jan 2009

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