Details

Autor(en) / Beteiligte

• Geller, Marvin A.
• Zhou, Tiehan
• Yuan, Wei

Titel

The QBO, gravity waves forced by tropical convection, and ENSO

Ist Teil von

• Journal of geophysical research. Atmospheres, 2016-08, Vol.121 (15), p.8886-8895

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2016

Quelle

Wiley Online Library - AutoHoldings Journals

Beschreibungen/Notizen

• By means of theory, a simplified cartoon illustrating wave forcing of the stratospheric quasi‐biennial oscillation (QBO), and general circulation modeling of the QBO, it is argued that the period of the QBO is mainly controlled by the magnitude of the gravity wave (GW) vertical fluxes of horizontal momentum (GWMF) forcing the QBO, while the QBO amplitude is mainly determined by the phase speeds of the GWs that make up this momentum flux. It is furthermore argued that it is the zonally averaged GWMF that principally determines the QBO period irrespective of the longitudinal distribution of this GW momentum flux. These concepts are used to develop a hypothesis for the cause of a previously reported El Niño–Southern Oscillation (ENSO) modulation of QBO periods and amplitudes. Some observational evidence is reported for the ENSO modulation of QBO amplitudes to have been different before the 1980s than after about 1990. A hypothesis is also given to explain this in terms of the different ENSO modulation of tropical deep convection that took place before the 1980s from that which occurred after about 1990. The observational evidence, while consistent with our hypotheses, does not prove that our hypotheses are correct given the small number of El Niños and La Niñas that occurred in the early and later periods. Further research is needed to support or refute our hypotheses. Key Points It is the parameterized gravity wave flux that mainly determines the period and amplitude of the QBO QBO periods are longer during times of La Niña than during times of El Niño QBO amplitudes were larger during La Niñas than during El Niños after about 1990, but this did not seem to be the case before the mid‐1980s