The Equatorial Quasi-Biennial Oscillation (QBO)

The QBO is a dominant interannual variation in the equatorial stratosphere. It is characterized as periodic variations of the easterly and westerly zonal-mean zonal wind with the period of about 2 year (e.g., Baldwin et al. 2001, Review of Geophysics).

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Zonal wind observed at Singapore

About the data

Radiosonde observations have been conducted at Singapore (1N/104E) from 1976 to present.
The monthly-mean zonal wind data is available from http://www.geo.fu-berlin.de/met/ag/strat/produkte/qbo/qbo.dat
Time-height section of the zonal wind:

Japanese description

QBO index

About the index

A representation of the QBO is derived from the monthly-mean zonal wind data, by following the method introduced by Wallace et al. (1993; Journal of the Atmospheric Sciences).

The data is deseasonalized by subtracting the monthly climatology.
First two principal components (PC1 and PC2) are derived from the EOF analysis based on the covariance matrix at each levels.
The data and EOFs used are from January 1976 to April 2017 (as of 8 June 2017).

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Jan. 1976 to Apr. 2017 [NetCDF]

Scatter plots of normalized PC1 and PC2 at 4-year intervals

Created: Jun. 05, 2017 by Eriko Nishimoto