Tropospheric and equatorial influence on planetary wave amplitude in the stratosphere (formerly paper P6.6)

We examine two possible factors affecting the amplitudes of extratropical planetary waves in the stratophere: tropospheric influence and equatorial influence, using 45-year NCEP/NCAR reanalysis data. Climatological time-mean results do not show significant difference of planetary-wave amplitudes in the extratropical stratosphere between the easterly and westerly QBO phases. This is because the variability of troposphere influence overwhelms the QBO effect. After this factor is removed, it is found that when the equatorial winds at 20, 15, and 10 mb are easterly, planetary-waves are generally amplified, while the waves are suppressed as the winds at the three levels are westerly. The effect of tropospheric influence and the QBO on major sudden warmings is also discussed.