Modulation of the Arctic Oscillation and the East Asian winter climate relationships by the 11-year solar cycle |
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Authors: | Wen Chen Qun Zhou |
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Institution: | Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100190 |
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Abstract: | The modulation of the relationship between the Arctic Oscillation (AO) and
the East Asian winter climate by the 11-year solar cycle was investigated.
During winters with high solar activity (HS), robust warming appeared in
northern Asia in a positive AO phase. This result corresponded to an
enhanced anticyclonic flow at 850 hPa over northeastern Asia and a weakened
East Asian trough (EAT) at 500 hPa. However, during winters with low solar
activity (LS), both the surface warming and the intensities of the
anticyclonic flow and the EAT were much less in the presence of a positive
AO phase. The possible atmospheric processes for this 11-year solar-cycle
modulation may be attributed to the indirect influence that solar activity
induces in the structural changes of AO. During HS winters, the sea level
pressure oscillation associated with the AO became stronger, with the
significant influence of AO extending to East Asia. In the meantime, the
AO-related zonal-mean zonal winds tended to extend more into the
stratosphere during HS winters, which implies a stronger coupling to the stratosphere. These
trends may have led to an enhanced AO phase difference; thus the associated
East Asian climate anomalies became larger and more significant. The situation tended to
reverse during LS winters. Further analyses revealed that the relationship between the winter
AO and surface-climate anomalies in the following spring is also modulated by the 11-year solar
cycle, with significant signals appearing only during HS phases. Solar-cycle variation should
be taken into consideration when the AO is used to predict winter and spring climate anomalies
over East Asia. |
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Keywords: | AO East Asian winter climate solar activity East Asian trough |
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