Data provided by Barbara Naujokat.

The contradicting results of these two observations remained a mystery for a half a century from then. In 1961, it was solved by Reed and independently by Veryard and Edbon. 4),5) They discovered that the wind in the equatorial stratosphere was changing direction in a 26-month cycle. The Krakatoa easterly and the Berson westerly were both correct. The oscillation of this wind, which has a cycle of a little more than two years, is called the Quasi-Biannual Oscillation (QBO). All that said, a 26 month cycle is certainly a strange length. A one or two year cycle would seem to make more sense, so where did this odd figure come from?