The NOAA IR serves as an archival repository of NOAA-published products including scientific findings, journal articles, guidelines, recommendations, or other information authored or co-authored by NOAA or funded partners.
As a repository, the NOAA IR retains documents in their original published format to ensure public access to scientific information.
i
Linear stability analysis of CISK-induced low latitude disturbances
-
1975
[PDF-106.48 MB]
Details:
-
Personal Author:
-
Corporate Authors:
-
NOAA Program & Office:
-
Description:The physical stability of perturbation motions in a conditionally unstable tropical atmosphere at rest is examined under CISK and frictional forcing. The governing linear multi-layer primitive equations are formulated into an eigenvalue problem for the unconditional heating case. This analysis yields propagation speeds, growth rates, and vertical structure for the modes supported by the model. The specified parameters are the vertical distribution of diabatic heating, the base state temperature structure, boundary layer specific humidity, lateral mixing coefficients for momentum and temperature, surface friction coefficient, coriolis parameter and perturbation wavelength. A variety of unstable quasibalanced modes are found, some of which have small e-folding times (on the order of days) with a cyclone scale preferred wavelength; for these modes a pronounced short wave cutoff is essentially independent of lateral mixing. For a welldelineated vertical heating profile, and certain values of the physical parameters, the vertical structure of these modes resembles that of the formative stage of a tropical cyclone. Internal gravity modes are found which are unstable; the external gravity mode damps in all cases. These results hold for both a three-layer and seven-layer model. With coarse vertical resolution, the results are strongly dependent on the vertical staggering of the dependent variables; increasing the vertical resolution of the model eliminates differences due to the choice of staggering. The equations for the three-layer model are numerically integrated as an initial value problem for both conditional and unconditional heating. The results indicate that the eigenvalue analysis for unconditional heating can be used as a predictor for instability under conditional heating. The integrations also show that the results are strongly dependent on lateral boundary conditions when a small domain is used, and that a domain in excess of 3000 km is preferred for the study of perturbations supported by this model atmosphere.
-
Keywords:
-
Series:
-
Document Type:
-
License:
-
Rights Information:CC0 Public Domain
-
Compliance:Library
-
Main Document Checksum:
-
Download URL:
-
File Type:
