The Anomalous Change in the QBO in 2015-16 (Invited Presentation)

The quasi-biennial oscillation (QBO) is a tropical lower stratospheric, downward propagating zonal wind variation, with a period of ~28 months. The QBO has been constantly documented since 1953. Here we describe the evolution of the QBO during the Northern Hemisphere winter of 2015-16 using radiosonde observations and meteorological reanalyses. Normally, the QBO would show a steady downward propagation of the westerly phase. In 2015-16, there was an anomalous upward displacement of this westerly phase from ~30 hPa to 15 hPa. These westerlies impinge on, or “cut-off” the normal downward propagation of the easterly phase. In addition, easterly winds develop at 40 hPa.  Comparisons to tropical wind statistics for the 1953-present record demonstrate that this anomalous 2015-16 QBO is unprecedented. We will also show the impact of the anomalous QBO to trace gas species in the tropics.