| dc.description |
By using the 160 stations monthly precipitation data and NOAA-ESRL reanalysis data, the effect of spring Antarctic Oscillation
(AAO) on Summer Precipitation in North China (SPNC) is studied. The analysis results show that the positive phase of March
AAO leads the easterly-southerly and ascend anomalies in the southern part of North China by affecting zonal wind, and
meridional circulation in the Northern Hemisphere (NH) late summer, results in more SPNC. Key regions of Antarctic sea-ice
may store preceding March AAO signal which is cross-seasonal sustained by the heat exchanging with underlying surface, and
the Summer Antarctic Sea-ice Index (SSI) is defined. The upward and poleward propagations of the planetary wave are enhanced
in the SouthernHemisphere (SH) high latitude, and there are significant anomalous variabilities of PSI over SH low latitude, high
latitude and polar regions in the high SSI years and vice versa. The wave-current interaction weakens the descendingmotion over
the Antarctic, strengthens the circumpolar westerlies and deepens the SH polar vortex (AAO positive phase) in the high SSI years
and vice versa. The results of observation and CAM5 show that SSI is positively correlated with indices of Quasi-Biennial
Oscillation (QBOI). In QBO westerly phase, the SPNC anomaly in the high SSI years shows out of phase with that in the low SSI
years. In the low SSI years, Rossby wave has the characteristics of anomalous southward propagation which corresponds to the
abnormal weakening of ascend motion (the decrease of precipitation) over North China. Accompanied with a significant PSI
anomaly, there exists a region of weak to strong wave energy over North China which is regarded as the source region of wave
energy in both high and low SSI years of QBO westerly phase. But in QBO easterly phase, SPNC anomaly is not significant.
QBO may be a bridge that connecting the signals of zonal wind anomalies in the stratosphere of the SH and the NH. |
|