Variability in QBO Temperature Anomalies on Annual and Decadal Time Scales

The stratospheric quasi-biennial oscillation (QBO) induces temperature anomalies in the lower stratosphere and tropical tropopause layer (TTL) that are cold when lower-stratospheric winds are easterly and warm when winds are westerly. Recent literature has indicated that these QBO temperature anomalies are potentially important in influencing the tropical troposphere, and particularly in explaining the relationship between the QBO and the Madden-Julian oscillation (MJO). The authors examine the variability of OBO temperature anomalies across several time scales using reanalysis and observational datasets. The authors find that, in boreal winter relative to other seasons, QBO temperature anomalies are significantly stronger (i.e., colder in the easterly phase of the QBO and warmer in the westerly phase of the QBO) on the equator, but weaker off the equator. The equatorial and subtropical changes compensate such that meridional temperature gradients and thus (by thermal wind balance) equatorial zonal wind anomalies do not vary in amplitude as the temperature anomalies do. The same pattern of stronger on-equatorial and weaker off-equatorial OBO temperature anomalies is found on decadal time scales: stronger anomalies are seen for 1999-2019 compared to 1979-99. The causes of these changes to QBO temperature anomalies, as well as their possible relevance to the MJO-QBO relationship, are not known.

Automated summary

The study found that in boreal winter, the temperature anomalies induced by QBO were stronger on the equator but weaker off the equator, with differences in amplitude compensating for meridional temperature gradients. Similar patterns were observed on decadal time scales, with stronger anomalies seen in the years 1999-2019 compared to 1979-99. The causes of these changes and their potential relevance to the MJO-QBO relationship remain unknown.