East Asian climate and Arctic/Antarctic Oscillations

1. East Asian climate and Arctic/Antarctic Oscillations Daoyi Gong (gdy@bnu.edu.cn) State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University

2. AO and East Asian climate • East Asian winter monsoon • East Asian summer monsoon • (b) Weather extremes/climate disasters

3. Climate meanings: Basic/fundamental state of free atmosphere: westerly flow What cause AO/AAO variability: … downward propagation of stratosphere anomalies … eddy-mean flow interaction, e.g., EP flux theory … stationary wave-mean flow interaction … troposphere thermal or dynamical forcing. e.g., Autumn snow in Siberian -> negative AO.

4. Changes of air temperature at 925 hPa level in association with a one unit of AO. Areas significant at 0.05 level are shaded and the high correlation center with |r|>0.6 indicated by darker shading. Contour intervals: 0.5C. Zero lines are omitted for clarity. ERA40 data

5. Changes of regional atmospheric circulation in association with a -1 unit of AO. Contours: 500hPa height, solid lines: positive anomalies, dashed lines are negative, unit is gpm. Vectors: horizontal wind at 850hPa level, maximum values are 2.4m/s. Shadings: air temperature at 925hPa, light shading: -0.5 to -1C; darker shading: cooler than lower -1C ERA40 data, DJF

6. Correlations among indices (DJF, 1880-2001)

7. Time-series of AO (a), Siberian High (b), East Asian Trough (c), and temperature in East China (d) since late 19th century

8. Winter influence on inter-annual to decadal time scale • AO influence on summer monsoon and monsoonal rainfall • AO modulation on high-frequency variability and extremes • in temperature • Negative phase AO: • Strong Siberian High due to • cooler Euasian continent in mid-high latitude, • enhanced downward air motion by convergence in upper level with the enhanced trough • …Strong winter monsoon • …Cooler East Asia.

9. Reg.<May AO, JJA rainfall> May AO and JJA Rainfall Data: 5x5 degree, global land (Hulme 1992) Grey squares: Data availability >95% during 1900-98 Shading: >95% c.l. Changes in summer precipitation (mm) corresponding to a one standard deviation of the May AO index.

10. Cross section of the zonal mean zonal wind (u), meridional wind (v) and vertical motion (ω) over East Asia (110ºE-150ºE) regressed onto the May AO index.

11. Spring NDVI Summer U200 • The first paired modes of singular value decomposition (SVD) analysis between spring normalized difference of vegetation index (NDVI) anomaly and summer zonal wind at 200 hPa (U200) anomaly • First-paired mode for NDVI • First-paired mode for U200. • Units are arbitrary. Contour interval is 0.02 and the 0 value line is omitted for clarity. • Mao et al., 2008

12. Cross section of the summer zonal mean zonal wind (u), meridional wind (v) and vertical motion (ω) over East Asia (100E-120E) regressed onto thespring NDVI-PC1. The u is shown as the contours with interval of 1 m/s. Regions above 95% confidence level are shaded. The covariance of v and ω are shown as vectors. Values are m/s for u and v, and hPa/s for ω. The values of largest vectors are 0.40 m/s for v and 1.3× 10-2 hPa/s for ω.

13. Dust storms Sea ice severity

14. AO and spring dust storm frequency in northern China (shown only the inter-annual components). Their Spearman correlation is –0.304.

15. Outline… • Winter influence on inter-annual to decadal time scale • AO influence on summer monsoon and monsoonal rainfall • AO modulation on high-frequency variability and extremes • in temperature Contour lines are regression of the synoptic variance of daily 850hPa heights upon dust storm frequency (F_D). Contour intervals: 0.5m. Zero contours are omitted for clarity. Shading areas are significant at the 95% level. Horizontal wind changes at 500 hPa level Maximum wind vectors are 1.8m/s.

17. Ice severity index AO Time-series of Sea ice severity in Bohai Sea and AO. DJF. AO x -1 normalized.

18. Jinzhou station, north Bohai Sea 2 1 > +1.2σ, 7 winters < -1.2σ, 6 winters • -12 days Less freezing days, where T < -4C

19. AAO and East Asian summer monsoon

20. (a) Correlation between the April–May AAO and June–August precipitation in China for the period 1951–2001. (b) Normalized time series of spring AAO and summer precipitation in Yangtze River valley. r = +0.49 Nan and Li 2003, GRL

21. …Cross-equatorial air flow in Indian Ocean …Cross-equatorial air flow in western Pacific …Troposphere Rossby waves ? …through influencing regional SST/Precipitation ?

22. A A A: anticyclone Water transport below 700hPa, wind vector at 850 hPa. JJA. ERA40 data

23. Regression coefficients of the ERA40 SLP upon the Sr-content time series during 1958–1993. The unit is hPa per standard deviation of Sr. Prior to analysis, the Niño3.4 SST signals were excluded from Sr-content time series.

26. Weekly cycles in atmosphere over China: Polluted weather ? Dao-Yi GONG1, Chang-Hoi HO2, Deliang CHEN3, Yun QIAN4, Yong-Sang CHOI2, and Jinwon KIM5 1 State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Resources Science & Technology, Beijing Normal University, 100875, China 2 School of Earth and Environmental Sciences, Seoul National University, Seoul 151-742,Korea 3 Earth Sciences Centre, Göteborg University, Guldhedsgatan 5A, Box 460, 405 30 Göteborg, Sweden 4 Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, WA 99352, USA 5 Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California, USA Gong et al., J.G.R., 2006; 2007

27. Anomalies of temperature from Sunday through Saturday. 29 stations, JJA, 2001-2006 Error bars are  1 standard error about the 29-sample mean.

28. Anomalous frequency of light rains from Sunday through Saturday. P 5mm/day, 29 stations, JJA, 2001-2006 Error bars are  1 standard error about the 29-sample mean.

29. Globe: Cities with more than 100,000 people in 1997 China: 448 with population >0.5 million, 174 with population >1 million. Most in East China. By 2003 Source: United Nations Statistics Division

30. PM10 PM10, JJA, 2001-2006. ‘’ : PM10 stations, ‘’: R2 grids, ‘O’: radio-sounding temperature stations

31. Radio-sounding T, R2 Profile of temperature anomaly from Sunday through Saturday in troposphere. Shown here is the mean of 15 radiosonde observations. Unit: C. 1100UTC. Profile of temperature anomaly from Sunday through Saturday in troposphere. Shown here is the mean of 29 R2 grids. Unit: C. Data sources: Durre et al., 2006. J. Climate, 19, 53-68

32. Anomaly of the daily mean vertical air velocity (ω) in the lower troposphere between 925 and 850 hPa levels at 29 R2 grids during 2001-2005.

33. Radio-sounding Anomaly of the horizontal wind velocity in lower troposphere between 925 and 850hPa levels, shown as the average from radiosonde observations. Error bars are  1 standard error about the sample mean. 1100UTC, data availability >90%. Data sources: Durre et al., 2006. J. Climate, 19, 53-68

34. Climate implication… 0.05 level 1956-2005. Whole China. JJA.

35. Climate implication… Regional mean trends [<10mm/day]: 1956-05: -1.7days/10yr [～20％] 1980-05: -2.4days/10yr, 0.01 level Linear trend of the number of light rain days during the time period 1956-2005. Unit: days/10yr. JJA.

36. Conclusion: • There are significant, consistent weekly cycles in meteorological variables in east China during summer , most likely connected to the weekly cycle of air pollution, and a result of aerosol-atmosphere interaction. • (2) The significant decreasing of light rains is likely related to the enhanced human activities, and suppressed by the increasing air pollution. • (3) …modelling validation

37. Variability of the low-level cross-equatorial jet of the western Indian Ocean since 1660 as derived from the coral proxies Dao-Yi Gong ( Beijing Normal University, China, gdy@bnu.edu.cn) Jürg Luterbacher (University of Bern, Switzerland, juerg@giub.unibe.ch) Gong & Luterbacher, G. R. L., 2008

38. Trend in the 20th century: A puzzling fact In association with climate warming A notably enhancing trend in wind in western Arabian Sea (Anderson et al. 2002, Science, 596) … and also suggested by some simulations (Hu et al., 2000)

39. Data: 8 coral proxies from Indian Ocean Basin Longest: ~1660AD O Grids of COADS July wind speed data →ERA40 climate wind vectors of 850hPa level in June-July-August. Mean meridional wind to define the cross-equatorial jet flow (i.e., V850). Coral sites. IFA: Ifaty (Zinke et al., 2004), SEY: Seychelles (Charles et al., 1997), NIN: Ningaloo (Kuhnert et al., 2000), PIR: Pirotan (Chakraborty and Ramesh, 1998), REU: Réunion (Pfeiffer et al., 2004), BAL: Bali (Charles et al., 2003), XIS: Xisha (Sun et al., 2004), BUN: Bunaken (Charles et al., 2003). Data from: http://www.ncdc.noaa.go/paleo [all are δ18O except XIS which is Sr]

40. Trend in the 20th century: A puzzling fact

41. Observed and simulated wind during the 20th century COADS surface wind, July only averaging from 8 grids IPCC AR4, V850, JJA Coupled models simulations for 20th century (20C3M) forced by observed natural and anthropogenic forcings. Ensemble of 21 models Only low-frequency shown. Shading: 2SE of the ensemble means. Data source: Zhou T J

42. Conclusion: Low-level Indian monsoon wind shows no enhancing tendency as global temperature rises during the 20th century.

43. Thanks !