• Introduction
• Data
• QBO phases
• Solar activity
• Composites with respect to the QBO phases
• Stratification according to the solar activity
• Concluding remarks
• References

FIGURES

• Figures 1a, 1b
• Figures 2a, 2b
• Figure 3
• Figures 4
• Figures 5a, 5b
• Figures 6a, 6b

1. Introduction

• In the northern stratosphere: (e.g. Holton and Tan 1980)
  • Colder, deeper vortex, stronger polar-night jet in the W
  • Opposite to the Holton-Tan Oscillation in the solar maximum
• In the southern stratosphere:
  • Large difference not in midwinter but in spring

2. Data

• NCEP/NCAR Reanalysis Data; 1958-1997
• 31-day running mean after calculating the EP flux

3. QBO phases

• Equatorial zonal wind (provided by Naujokat)
• Phases definition - 20-30hPa average in July
• "W": westerly phase / "E": easterly phase
• Sign of the composite difference: W minus E

4. Solar activity

• Solar 10.7cm flux data (from WDC-A) in July
• "Min": less than 120 / "Max": more than 140
• Sign of the composite difference: Max minus Min

5. Composites with respect to the QBO phases

5-1: Latitude-time sections

Figures 1a -1b

Upper: Zonal wind at 50 hPa. Large positive difference in November means that the polar-night jet is stronger in the W, that is, the deceleration in this season occurs earlier in the E.
Lower: Zonal wind at 300hPa. Positive signal moves slowly from the equator to the higher latitudes during winter and spring.

5-2: Meridional sections

Figure 2a - 2b

Upper: Monthly mean zonal wind. Large positive difference appears near the equator in August, and moves poleward and downward to be found at 50hPa in November.
Lower: EQ flux (vectors) and its divergence (color tone). The vectors are divided by ? a cos ?. Downward vectors and blue tone around 60S indicate larger upward flux and larger convergence in the E.

5-3: Schematic view

Figure 3

Schematic illustration for considering income and outgo of the momentum for the "boxes". In the upper box, the large convergence is associated with the large income from the lower box. As for the lower box, the relationship between the upward outgo to the upper box and the equatorward one is interesting.

5-4: Time series

Figure 4

(a) Zonal wind at 50hPa, 60S. (b) EP flux divergence at the same. (c) Up;ward flux at 100hPa. (d) Equatorward flux at 40S. (e) Zonal wind at 300hPa, 40S.
Note that the planetary-scale compornents are dominant for (c) while the larger wavenumber components are dominant for (d).

6. Stratification according to the solar activity

6-1: QBO composites (W minus E) for the solar Min and Max years

Figures 5a - 5b

Composites with respect to the QBO phases by using only the Min years (upper) or the Max years (lower) for the zonal wind at 50hPa. Unlike the NH, the difference between the W and the E in the SH seems to be independent of the solar activity.

6-2: Solar composites (Max minus Min) for the QBO W and E years

Figures 6a - 6b

Composites with respect to the solar activity by using only the W years (upper) or the E years (lower) for the zonal wind at 50hPa. Unlike the NH, the difference between the Max and the Min in the SH seems to be independent of the QBO phases.

7. Concluding remarks

• The QBO effect on the polar-night jet in the SH is closely related to that on the planetary wave propagation from the troposphere.
• The momentum flux in the troposphere is also correlated with the QBO phases.
• The effect of the QBO and that of the solar activity seem to be independent of each other.

8. References

• Baldwin, M. P. and T. J. Dunkerton, 1998: Geophys. Res. Lett., 25, 3343-3346.
• Holton, J. R. and H.-C. Tan, 1980: J. Atmos. Soc., 60, 124-139.
• Labitzke, K. and H. van Loon, 1988: J. Atmos. Terr. Phys., 60, 124-139.
• Naito, Y. and I. Hirota, 1997: J. Meteor. Soc. Japan, 60, 124-139.
• Naito, Y. and I. Hirota, 2000: (in preparation)