Science Update: A satellite perspective of the interaction between the QBO and gravity waves

M. Ern and co-authors present a new study in JGR using satellite observations to improve the representation of the quasi-biennial oscillation (QBO) in models. This improvement requires a better understanding of the driving of the QBO by atmospheric waves, which remains highly uncertain because of the small horizontal scales involved and because no direct estimation based on global observations yet exists. They derive gravity wave momentum fluxes from temperature observations form the HIRDLS and SABER satellite instruments, and show that waves with wavelengths <10km interact most strongly with the QBO. They estimate gravity wave drag and compare this to the missing drag in the tropical momentum budget of ERA-Interim. During eastward wind shear the observations agree well with ERA-Interim, however, during westward wind shear the observations are two times lower than ERA-Interim. This possibly suggests that uncertainties in the ERA-Interim advection terms remain. They find that the tropical gravity waves are strongly intermittent and thus may play in important role in terms of QBO formation. This may have important implications for gravity wave parameterisation in models. The full abstract can be found here.