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Physical Processes of the Influence of 11-year Solar Cycle on the East Asian Winter Climate Wen Chen, and Qun Zhou Institute of Atmospheric Physics, CAS, Beijing, China Slide 2 EAWM system: EA jet EA trough, Siberian High, Aleutian Low, Low-level northeasterlies Slide 3 Center for Monsoon System Research, IAP, CAS Many previous studies focused on the winter monsoon surges - the synoptic-scale features associated with the EAWM (Wu and Chan, 1995, 1997; Zhang et al., 1997) The interannual to interdecadal variations of the EAWM has been related to El Nio-Southern Oscillation (ENSO) (e.g., Zhang et al. 1996; Chen et al., 2000; Wang et al. 2000; Wu and Chan, 2000; Chan and Li 2004). Arctic Oscillation (AO) (e.g., Gong et al. 2001; Chen and Kang, 2006; Wu et al. 2006). Slide 4 Center for Monsoon System Research, IAP, CAS The El Nio-Southern Oscillation (ENSO) is regarded as the most important factor that influences the East Asian winter climate. El Nio warm and wet La Nia cold and dry (McBride et al., 2003; Hamada et al., 2002; Lau and Nath, 2003) (From Ashok and Yamagata 2009) Slide 5 The Arctic Oscillation (AO) is the dominant mode of wintertime atmospheric variability in the Northern Hemisphere. Its impact can extend to East Asia, modulating the frequency of cold surges [Jeong and Ho, 2005] and the intensity of the East Asian winter monsoon [Chen et al., 2005; Gong et al., 2001]. Arctic Oscillation Positive AO weak EAWM with warming in the northern China Negative AO strong EAWM Slide 6 Solar influence on ENSOSolar influence on ENSO (Kryjov and Park, 2007; Calvo and Marsh, 2011; Kodera, 2005, 2007) Solar influence on the AO/NAOSolar influence on the AO/NAO (Kodera, 2003; Ogi et al., 2003; Gimeno et al., 2003) Recent studies indicated that the modes of climate variation can be influenced by the solar cycle. Are the relationships of East Asian winter climate anomalies with ENSO or the AO affected by the 11-year solar cycle? Slide 7 Center for Monsoon System Research, IAP, CAS Solar cycle modulation of the ENSO impact on the winter climate of East Asia Influence of the solar cycle on the relationship between the AO and East Asian winter climate Slide 8 DJF 160 Correlation between the surface temperature of 160 Chinese observation stations and the F10.7 cm for DJF mean during 1959 to 2010. Slide 9 ENSO and the East Asian winter climate ENSO and the East Asian winter climate A Slide 10 More robust ENSO - EAWM relationship during the LS years! HS Surface temperature Precipitation LS Solar cycle modulation Solar cycle modulation Slide 11 SLP UV850 H500 A A C C Solar cycle modulation Solar cycle modulation More robust ENSO - EAWM relationship during the LS years! Slide 12 HSLS MAM(0) JJA(0) SON(0) DJF SSTA evolutions during the HS and LS years SSTA evolutions during the HS and LS years Slide 13 (Meehl et al., 2007) Slide 14 HS (1957, 1968, 1979, 1989, 2000) LS (1964, 1975, 1986, 1995, 2008) A La Nina like SST pattern in the Pacific tends to be forced in the HS. SSTAs in the HS and LS winters SSTAs in the HS and LS winters Slide 15 (Wang et al., 2000) The mechanism of the anomalous WNP anticyclone: (1) the local air-sea interaction Slide 16 Tropospheric temp, surface wind & rainfall IO warming Warm Kelvin wave into the WP Northeasterly winds to the north under friction Divergence over NW Pacific Suppressed convection The mechanism of the anomalous WNP anticyclone: (2) the Indian Ocean warming mechanism (Xie et al., 2009) Slide 17 Kaplan SLP HadISST CRUTEM3 SST SLP SST SLP TS Extended period analysis confirms the solar cycle modulation Extended period analysis confirms the solar cycle modulation Slide 18 Center for Monsoon System Research, IAP, CAS Solar cycle modulation of the ENSO impact on the winter climate of East Asia Influence of the solar cycle on the relationship between the AO and East Asian winter climate Slide 19 r=0.232 AO Solar cycle H/+ L/+ Slide 20 T850 160Ts H500 During the positive AO winters, lower tropospheric temperature tended to be abnormally warmer over northeastern Asia with a weakened trough. Relationship between AO and EAWM Relationship between AO and EAWM Slide 21 Weakened (Chen et al., 2005, JGR) Enhanced W-acceleration W-deceleration Arctic Oscillation Negative AO phase Strengthed SH and AL Strong EAWM Weakened Slide 22 During the HS winters, both the domain and strength of T anomalies enlarged in relation to the AO. The same is true for the East Asian trough. HS LS Influence of Solar Cycle on AO-EAWM Relationship Influence of Solar Cycle on AO-EAWM Relationship T850 H500 Slide 23 Why is the AO-EAWM relationship dependent on the solar cycle? The AO tends to be more active during an HS winter with more significant influence on East Asia. Discussion-(1) Slide 24 Extend farther into stratosphere Zonal-mean zonal wind To suggest more pronounced coupling between S&T in an HS winter. Discussion-(2) Slide 25 Differences of mean flow and waves between HS and LS LSHSHS-LS Zonal-mean TZonal-mean U A weak and warm polar vortex in relation to an HS winter More planetary waves propagating into polar region Weak Warm Slide 26 1hPa 10 100 S EQ N Radiation heating U Planetary wave propagation Weak and warm Polar vortex AO Direct influence More close AO- EAWM relation O 3 content variation T gradient change Thermal wind theorem Strong S-T coupling Chen and Zhou, AAS, 2012 Slide 27 Certain extreme stratospheric anomalies associated with AO (e.g., major warming) can propagate downward and influence the tropospheric weather regimes (Baldwin and Dunkerton, 2001). Baldwin and Dunkerton, 2001 Cold air outbreaks in the NH are associated with the stratospheric weak polar vortex events. The stratospheric polar vortex contains information that can be used to enhance forecasts of cold air outbreaks (Kolstad et al., 2010). Slide 28 Summary Both the relations of EA winter climate to the ENSO and AO are modulated by the 11-year solar cycle. ENSO and EA climate relationship is more robust during the LS winters. Possible mechanism of this influence is that an anomalous WNP anticyclone is intensified. However, during the HS winters, more robust warming appeared in northern Asia in a positive AO phase. Our results suggest that the solar cycle modulation appear to result from an indirect influence via the AO structural change. The solar cycle variation should be taken into consideration when ENSO and AO are used to predict the EA climate. Thank you!