Does the Solar Cycle Increase or Decrease the Period of the Quasi-Biennial Oscillation? A Modeling Study Le Kuai 1, Runlie Shia 1, Xun Jiang 2, Ka-Kit Tung 3, Yuk L. Yung 1 Le Kuai 1, Runlie Shia 1, Xun Jiang 2, Ka-Kit Tung 3, Yuk L. Yung 1

1)Pascoe, et al. (2005), Salby and Callaghan (2000): westerly period of the equatorial QBO longer during the solar min 2)Soukhrarew and Hood’s (2001): both phases of QBO periods were longer during SC-min. 3)Fisher, and K.K. Tung (2007) that the anti-correlation of QBO period with the solar cycle mentioned by Salby and Calleghan breaks down in the solar min of 1997 with QBO period as low as about 25 months when there were no major volcanic perturbations. 1)Pascoe, et al. (2005), Salby and Callaghan (2000): westerly period of the equatorial QBO longer during the solar min 2)Soukhrarew and Hood’s (2001): both phases of QBO periods were longer during SC-min. 3)Fisher, and K.K. Tung (2007) that the anti-correlation of QBO period with the solar cycle mentioned by Salby and Calleghan breaks down in the solar min of 1997 with QBO period as low as about 25 months when there were no major volcanic perturbations. Previous work

Advantage of model Provide longer time period (82 yr, more than 6 solar cycle) Without volcanic influence in the simulation Provide the solar radiation perpetual condition

The run with solar-min perpetual condition  Total QBO period is lengthened  Both phase durations are increased  Westerly descent rate < 1 month delayed; Easterly descent rate ~ 5 months longer  Total QBO period is lengthened  Both phase durations are increased  Westerly descent rate < 1 month delayed; Easterly descent rate ~ 5 months longer The run with five-time solar- max perpetual condition

FFT analysis of equatorial zonal wind at 30 hPa QBO period: 5xSC-max > 1xSC-max > 1xSC-min QBO period: 5xSC-max > 1xSC-max > 1xSC-min

Increasing trend due to enlarged solar radiation Above 30 hPa: Easterly > Westerly Below 30 hPa: Westerly > Easterly  NCEP: E-QBO/W-QBO gradually decrease/increase from 10 hPa ~ 50 hPa  Model: Constant at upper three levels  Both see the stalling at 50 hPa W-QBO longer than E-QBO  The stalling is strengthened by solar radiation  NCEP: E-QBO/W-QBO gradually decrease/increase from 10 hPa ~ 50 hPa  Model: Constant at upper three levels  Both see the stalling at 50 hPa W-QBO longer than E-QBO  The stalling is strengthened by solar radiation

More sudden warming events during solar max years Brewer Dobson circulation stronger in solar-max condition Brewer Dobson circulation stronger in solar-max condition More downdraft at polar region Upwelling at equatorial lower stratosphere Slow down the critical line descent rate

 A positive correlation between the lengthen of QBO period and the solar cycle flux  Each phase duration is extended. Stronger elongation in E-QBO above 30 hPa but in W-QBO below this level.  Easterly phase stalling is stronger during larger solar radiation.  A positive correlation between the lengthen of QBO period and the solar cycle flux  Each phase duration is extended. Stronger elongation in E-QBO above 30 hPa but in W-QBO below this level.  Easterly phase stalling is stronger during larger solar radiation. Conclusions:

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