| Abstract from DBPedia | The quasi-biennial oscillation (QBO) is a quasiperiodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. The alternating wind regimes develop at the top of the lower stratosphere and propagate downwards at about 1 km (0.6 mi) per month until they are dissipated at the tropical tropopause. Downward motion of the easterlies is usually more irregular than that of the westerlies. The amplitude of the easterly phase is about twice as strong as that of the westerly phase. At the top of the vertical QBO domain, easterlies dominate, while at the bottom, westerlies are more likely to be found. At the 30mb level, with regards to monthly mean zonal winds, the strongest recorded easterly was 29.55 m/s in November 2005, while the strongest recorded westerly was only 15.62 m/s in June 1995.成層圏準2年周期振動（せいそうけんじゅんにねんしゅうきしんどう、quasi-biennial oscillation：QBO）とは、赤道域の成層圏での風系が約2年周期で規則的に変動する現象のことである。アメリカのR.J. ReedとイギリスのR.A. Ebdonによりそれぞれ独立に発見された。 (Source: http://dbpedia.org/resource/Quasi-biennial_oscillation) |
