1. Interdecadal Variability of East Asian Summer Monsoon and Precipitation By Huijun Wang Institute of Atmospheric Physics 2011-07-25

2. EAAM –seasonal migration of the rainbelt Averaged monthly rainfall 1979 through 2006 (http://svs.gsfc.nasa.gov)

3. EAAM –seasonal migration of the rainbelt

4. Changes in observed precipitation, 1951-2000 Courtesy of T. Zhou

5. The East Asian monsoon experienced an interdecadal change at the end of 1970s Wang H. J., 2001: The Weakening of the Asian Monsoon Circulation after the End of 1970’s, Adv. Atmos. Sci.,18, 376-386.

6. The East Asian summer monsoon index （ Wang, 2001, AAS; Wang, 2002, AAS ）

7. Area ： 110-125E, 20-40N Index of wind speed ： Data ： NCEP reanalysis

8. Variability of the East Asian winter monsoon index

9. Recent interdecadal Variation of the summer precipitation in eastern China

10. Background Interdecadal variability: a main contributor to the variation in the summer rainfall in East China; ▫Late 1970’s change – global scale; southern flood and northern drought (Wang 2001; Wu and Wang 2002; Han and Wang 2007; Ding et al. 2009; ……).  Possible contributors: global SST (Fu et al., 2009); PDO; Indian and Atlantic Ocean SST (Li et al. 2001; Yang and Lau 2004; Dong et al. 2006; Li et al. 2008; Wang et al. 2009; ……); snow cover over the Tibetan Plateau (Ding et al., 2008); Arctic sea ice and Eurasian snow; ……  No consistent conclusion

11. Recent changes in regional and global climate: (Kwon et al. 2007; Cummins et al. 2005; Bratcher and Giese 2002; Peterson and Schwing 2003; Swanson and Tsonis 2009; Easterling and Wehner 2009; ……). ▫Early 1990’s (south China rainfall increase); ▫Late 1990’s and beginning of 21st century (other regions  China: a new interdecadal period?)

12. Data and the model employed (1) the 160-station precipitation dataset from the China Meteorological Administration; (2) the soil moisture, horizontal and vertical wind, specific humidity, geopotential height and air temperature from the NCEP/NCAR reanalysis; (3) the Hadley Centre sea surface temperature (SST); (4) the PDO index from the website http://jisao.washington.edu/pdo/ http://jisao.washington.edu/pdo/ Model: IAP 9L_AGCM 4° lat × 5° lon (Bi 1993; Wang and Bi 1996)

13. Results of the study (1) Features of the summer precipitation pattern changes (2) Regional circulation (3) Background circulation (4) Sea Surface Temperature (5) AGCM experiments

14. HR: 32-36°N, 110-121°E YR: 28-31°N, 110-121°E SC: 22-26°N, 110-121°E percentage of the rainfall departure from the 1951- 2008 summer mean (7- year smoothed) (1) Features of the summer precipitation pattern changes

15. difference between 2000-2008 and 1979-1999 (a) station precipitation; (b) soil moisture (reanalysis) - + + - + + Consistent change patterns.

16. (a) 850 hPa omega; (b) vertically integrated water vapor content ; (c) vertically integrated (1000-300 hPa) moisture flux ; (d) climatology of (c). (2) Regional circulation Difference in the moisture flux divergence: HR-(- 0.78); YR-(0.29) (Sun et al., 2010)

17. (3) Background circulation (a) 500 hPa gph; (b) WPSH; (c) 200 hPa jet; (d) Temperature gradient.

18. (4) Sea Surface Temperature SST difference and PDO index

19. Correlation map between the summer-mean PDO index and 500 hPa geopotential height during 1979-2008 Consistent with the Warming center over Lake Baikal

20. (5) AGCM experiments 控制试验： 1980-2008 年平均的夏季海温 敏感性试验：方框区域内的海温差值叠加控制试验海温

21. 500 hPa hgt Observation Model

22. surface air temperature Observation Model

23. Precipitation Transport of water vapor （ 850 hPa wind ） ObservationModel

24. Summary Two interdecadal variation: one in the end of 1970s, another around 1999 After 1999, the summer precipitation in eastern China has changed significantly, with reduced rainfall over the middle-and-lower reaches of Yangtze River Basin The interdecadal change after 1999 is possibly related to variation of PDO, which is supported by the AGCM experiments with prescribed SST anomalies