There are interesting changes going on in the upper atmosphere with blocking becoming more and more of a feature over the North Atlantic.

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For the first time in a fair few months, the NAO is tanking. May this be a reaction to the shift from west to east in the QBO and this being a reaction of the solar downturn? Perhaps. Will be watching for a TREND.  If the GFS is correct then the incoming low Friday into Saturday across the northern UK looks set to change the shape of our pattern through next week with a chilly northerly flow on the rear of the low. Expect a cool, wet and windy weekend and a cool, showery week next week.  As for next week, that low becomes a larger feature over Scandinavia, acting like a giant wheel that will pull down late summer arctic air into the UK and much of Europe in fact. This setup with blocking high pressure near Greenland/Iceland and low pressure over Scand looks to be our pattern next week. The first chilly week in a few months. Next Wed/Thur (GFS)  GFS ensemble 500mb height anomaly (7-day mean) supports the firm -NAO with strong positive over Greenland/large vortex over Scandinavia. Wouldn’t this is fun if it were winter?  Week 2 shows weakening and westward shift in the blocking high into NE Canada but still teleconnects to a W Europe negative with cool/unsettled over Ireland, UK and western mainland.

QBO wind is turning from west to east.

The Quasi-Biennial-Oscillation (QBO) Data Serie

Data Compilation

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).

Data access

The data files are in ASCII format and can be downloaded bellow. The archive files (*.zip and *.tgz) contain the files: qbo.dat, singapore.dat, singapore2012.dat, and singapore2013.dat.

• qbo.dat            (starting 1953)
• singapore.dat  (starting 1987)
• singapore2013.dat
• singapore2014.dat
• qbo_data_zip.zip
• qbo_data_tgz.tgz

The QBO time series is updated until June 2014.

Note: Depending on your browser configuration it might happen that the data files, due to the file suffix .dat, will be related to the quicktime application. In this case please use the possibility to save the data files on your hard disk (right click, save link as …) before open them with a text editor.

Structure of the QBO

The time-height section derived from these data in Fig.30 shows the observed structure of the QBO at equatorial latitudes:

• alternating easterly and westerly wind regimes propagate downward with time;
• westerlies move down faster and more regularly than easterlies;
• the transition to easterlies is often delayed between 30 and 50 hPa;
• easterlies are generally stronger (30-35 m/s) than westerlies (15-20 m/s);
• maximum amplitudes of both phases typically occur near 20-hPa;
• the average period is about 27 months;
• both period and amplitude considerably vary from cycle to cycle.

Figure 1: Time-height section of monthly mean zonal winds (m/s) at equatorial stations: Canton Island, 3°S/172°W (Jan 1953 – Aug 1967), Gan/Maledive Islands, 1°S/73°E (Sep 1967 – Dec 1975) and Singapore, 1°N/104°E (since Jan 1976). Isopleths are at 10 m/s intervals; westerlies are shaded (updated from Naujokat, 1986) (download pdf).

Detailed information on all aspects of the QBO, its dynamics and its global effects, can be found in a most recent review paper of Baldwin et al (2001), including a comprehensive bibliography. A study of the coupling between the tropical QBO and the global stratospheric circulation has been performed by Marquardt (1998).

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