A mechanistic model study of slowly propagating coupled stratosphere-troposphere variability

Citation
K. Kodera et Y. Kuroda, A mechanistic model study of slowly propagating coupled stratosphere-troposphere variability, J GEO RES-A, 105(D10), 2000, pp. 12361-12370
Citations number
27
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Volume
105
Issue
D10
Year of publication
2000
Pages
12361 - 12370
Database
ISI
SICI code
Abstract
Observational studies reveal the oscillatory nature of coupled stratosphere -troposphere variability, which is characterized by a slowly downward propa gating anomalous zonal-mean zonal wind during the winter. The term "slowly" is employed compared to the rapid variation associated with stratospheric sudden warmings. In fact, strong stratospheric warming events are embedded in this slowly propagating variability as is shown in a companion paper [Ko dera et al., this issue]. In the present study, the mechanism producing suc h variability at all levels of the atmosphere is investigated by developing a simple model that extends from the Earth's surface to 80 km altitude. Th e model is a quasi-geostrophic channel model similar to that used by Holton and Mass [1976], but it includes two meridional Fourier components and lat itudinal variation in the gradient of the Coriolis parameter. By this exten sion, the present model can incorporate both the subtropical and polar nigh t jet and also treat the horizontal propagation of planetary waves as well as vertical propagation. The results of the simulation reproduce qualitativ ely well the main observed features: Interaction between the planetary wave s and zonal-mean flow produces oscillations in the winter stratosphere, and zonal wind anomalies created in the subtropics of the stratopause propagat e downward into the polar region of the troposphere, which provoke changes in the meridional propagation of tropospheric planetary waves.