Quasi-Biennial Oscillation (QBO) Zonal Wind Index, 1953-present

[Text Source: Freie Universitat Berlin, http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/qbo/ ]

Almost 50 years ago, the Quasi-Biennial Oscillation (QBO) of the winds in the equatorial stratosphere was detected due to the establishment of a global, regularly measuring radiosonde network (Graystone, 1959; Ebdon, 1960).

As part of the compilation of our daily stratospheric charts we have tabulated the daily wind observations of selected stations near the equator since 1957. For the earlier years, the values were extracted from the Northern Hemisphere Data Tabulations. From these daily values the monthly mean zonal wind components were calculated for the levels 70, 50, 40, 30, 20, 15, and 10 hPa and a data set from 1953 to the present was produced by combining the observations of the three radiosonde stations Canton Island (closed 1967), Gan/Maledive Islands (closed 1975), and Singapore (data file: qbo.dat).

This data set is supposed to be representative of the equatorial belt since all studies have shown that longitudinal differences in the phase of the QBO are small. It should be noted, however, that some uncertainties arose at higher levels during the early years from the scarcity of observations. More information on the original data can be found in Naujokat (1986).

A second data set has been produced since 1987 from the Singapore data by using the daily vertical wind profiles to obtain a higher vertical resolution. In this set you will find the monthly mean zonal wind components at Singapore for every year from 1987 to the present at the levels 100 (since 1997), 90, 80, 70, 60, 50, 45, 40, 35, 30, 25, 20, 15, 12, and 10-hPa (singapore.dat).