Descent Rate Models of the Synchronization of the Quasi-Biennial Oscillation by the Annual Cycle in Tropical Upwelling

Author: 

Rajendran, K
Moroz, I
Osprey, S
Read, P

Publication Date: 

July 2018

Journal: 

JOURNAL OF THE ATMOSPHERIC SCIENCES

Last Updated: 

2019-04-27T03:13:23.007+01:00

Issue: 

7

Volume: 

75

DOI: 

10.1175/JAS-D-17-0267.1

page: 

2281-2297

abstract: 

The response of the Quasi-Biennial Oscillation (QBO) to an imposed
mean upwelling with a periodic modulation is studied, by modelling the
dynamics of the zero wind line at the equator using a class of equations
known as ‘descent rate’ models. These are simple mathematical models that capture the essence of QBO synchronization by focusing on the
dynamics of the height of the zero wind line. A heuristic descent rate
model for the zero wind line is described, and is shown to capture many
of the synchronization features seen in previous studies of the QBO. Using a simple transformation, it is then demonstrated that the standard
Holton-Lindzen model of the QBO can itself be put into the form of a
descent rate model if a quadratic velocity profile is assumed below the
zero wind line. The resulting non-autonomous ordinary differential equation captures much of the synchronization behaviour observed in the full
Holton-Lindzen partial differential equation. The new class of models
provides a novel framework within which to understand synchronization
of the QBO, and we demonstrate a close relationship between these models and the circle map well-known in the mathematics literature. Finally,
we analyse reanalysis datasets to validate some of the predictions of our
descent rate models, and find statistically significant evidence for synchronization of the QBO that is consistent with model behaviour.

Symplectic id: 

831364

Download URL: 

Submitted to ORA: 

Submitted

Publication Type: 

Journal Article