>This is a more recent description [1]V. S. Babu and G. Ramkumar, “Planetary waves–major forcing agent in generating stratospheric and mesospheric quasi biennial oscillation,” CURRENT SCIENCE, vol. 106, no. 9, p. 1260, 2014. http://www.currentscience.ac.in/Volumes/106/09/1260.pdf

Frankly I have problems with this article. In particular the QBO visualizations on page 3 are decribed with two time intervals one extending over two years (which looks more likely) and one extending over ten years, but this seems not to be just a typo that is the visualization capture says explicitly again that the visualization extends over ten years.

>As it turns out, the other component in QBO is what they call a Semi-Annual Oscillation (SAO)

>The theory of the QBO

The Gif animation is a very nice visualization! It seems you have quite a talent for detecting special webpages. In particular as a matter of fact one can't find this webpage via a [search
on the main page](http://www.nerc.ac.uk/site/search/index.asp?q=QBO). I find it only irritatating that they seem to use red and blue for wind speeds into the east or west direction (minus is east). Especially with the bar below and the corresponding numbers one can very easily mistake that as temperatures, since this color choice is meanwhile quite hardwired for temperatures in visualizations. But then this is a 20 year old visualization from 1994! And yes it looks in those visualization as if the semiannual pressure oscillation is exactly semiannual (and the QBO exactly biannual, especially in the 200mB region the exact annuity is rather good visible).

>"Holton and Lindzen (1972) were the first to propose a model of the QBO based on vertically propagating waves. Originally it was thought that the Semi Annual Oscillation (SAO) in the upper stratosphere played an important role in the QBO. More recently they showed that while the SAO was important, it was not necessary for the formation of the QBO.The mechanism was further explained by Plumb (1977) who showed that the maximum acceleration occurs just below the maximum phase speed, leading to descent of the maximum with time. "

I don't understand though what they mean with: "who showed that the maximum acceleration occurs just below the maximum phase speed, leading to descent of the maximum with time. "
and their other explanations like:

>The more freely propagating westerlies are dissipated at higher altitudes and produce a westerly acceleration leading to a new westerly regime

From the visualization it looks to me on a first glance as if there is semiannually (In winter from south and in summer from north) easterlies (blue) "pouring down" from the stratosphere in the course of a quarter year (yes thats strange but thats how it looks) alternating with westerlies in autumn from north and in spring from south. And every second year the easterlies are not "strong enough" (in even years) to leave a "blotch" around the equator at around 20-30mB (which gives the QBO). Would be interesting to see that wind profiles together with temperature measurements....but given the state of temperature measurements I have some doubts that those exist, but may be I am wrong, satellite-drone galore or balloons???