Effect of the Kinematic Lower Boundary Condition on the Spectral and Autocorrelation Structure of Annular Variability in the Troposphere.

Kunz, Torben and Greatbatch, Richard John (2014) Effect of the Kinematic Lower Boundary Condition on the Spectral and Autocorrelation Structure of Annular Variability in the Troposphere. Open Access Journal of the Atmospheric Sciences, 71 (6). pp. 2264-2279. DOI 10.1175/JAS-D-13-0104.1.

[img]
Preview
Text
kunz_greatbatch14.pdf - Published Version

Download (933Kb) | Preview

Supplementary data:

Abstract

The dynamical origin of the spectral and autocorrelation structure of annular variability in the troposphere is investigated by a deductive approach. Specifically, the structure of the power spectrum and autocorrelation function of the zonal-mean geopotential is analyzed for the case of a quasigeostrophic spherical atmosphere subject to a white noise mechanical forcing applied in a single Hough mode and concentrated at a particular level in the vertical, with vertically uniform Newtonian cooling and Rayleigh drag concentrated at a rigid lower boundary. Analytic expressions for the power spectrum are presented together with expressions for an approximate red noise (i.e., a Lorentzian-shaped) power spectrum. It is found that for an infinitely deep atmosphere the power spectrum can be well approximated by a red noise process for the first few Hough modes (associated with large Rossby heights), provided the distance from the forcing is not larger than about one Rossby height. When a frictional rigid lower boundary is included, however, the approximation is generally bad. The high-frequency part of the power spectrum exhibits near-exponential behavior and the autocorrelation function shows a transition from a rapid decay at short lags to a much slower decay at longer lags, if the thermal and mechanical damping time scales are sufficiently well separated. Since observed annular variability exhibits the same characteristics, the above results lead to the hypothesis that these characteristics may, to some extent, be intrinsic to the linear zonal-mean response problem—although the need for an additional contribution from eddy feedbacks is also implied by the results.

Document Type: Article
Additional Information: WOS:000336882900022
Keywords: Annular mode, Troposphere, Boundary conditions
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/JAS-D-13-0104.1
ISSN: 0022-4928
Projects: Future Ocean
Date Deposited: 06 Jun 2014 09:38
Last Modified: 16 Apr 2018 11:43
URI: http://oceanrep.geomar.de/id/eprint/24702

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...