Climate of the Past www.clim-past.net 1814-9324 1814-9332 4 4 2008 10.5194/cp-4-225-2008 http://www.clim-past.net/4/225/2008/ http://www.clim-past.net/4/225/2008/cp-4-225-2008.html http://www.clim-past.net/4/225/2008/cp-4-225-2008.pdf 225 233 2008-11-03 Forced and internal modes of variability of the East Asian summer monsoon J. Liu jianliu@niglas.ac.cn B. Wang J. Yang State Key Laboratory of Lake Science and Environment, NIGLAS, Nanjing, 210008, China Department of Meteorology and IPRC, University of Hawaii at Manoa, Honolulu, HI 96822, USA Guest Professor, CPEO, Ocean University of China, Qingdao 266100, China State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China The modern instrumental record (1979–2006) is analyzed in an attempt to reveal the dynamical structure and origins of the major modes of interannual variability of East Asian summer monsoon (EASM) and to elucidate their fundamental differences with the major modes of seasonal variability. These differences are instrumental in understanding of the forced (say orbital) and internal (say interannual) modes of variability in EASM. We show that the leading mode of interannual variation, which accounts for about 39% of the total variance, is primarily associated with decaying phases of major El Nino, whereas the second mode, which accounts for 11.3% of the total variance, is associated with the developing phase of El Nino/La Nina. The EASM responds to ENSO in a nonlinear fashion with regard to the developing and decay phases of El Nino. The two modes are determined by El Nino/La Nina forcing and monsoon-warm ocean interaction, or essentially driven by internal feedback processes within the coupled climate system. For this internal mode, the intertropical convergence zone (ITCZ) and subtropical EASM precipitations exhibit an out-of-phase variations; further, the Meiyu in Yangtze River Valley is also out-of-phase with the precipitation in the central North China. <BR /> <BR /> In contrast, the annual cycle forced by the solar radiation shows an in-phase variation between the ITCZ and the subtropical EASM precipitation. Further, the seasonal march of precipitation displays a continental-scale northward advance of a southwest-northeastward tilted rainband from mid-May toward the end of July. This coherent seasonal advance between Indian and East Asian monsoons suggests that the position of the northern edge of the summer monsoon over the central North China may be an adequate measure of the monsoon intensity for the forced mode. Given the fact that the annual modes share the similar external forcing with orbital variability, the difference between the annual cycle and interannual variation may help to understand the differences in the EASM variability on the orbital time scale and in the modern records. Adler, R. F., Huffman, G. J., Chang, A., Ferraro, R., Xie, P., Janowiak, J., Rudolf, B., Schneider, U., Curtis, S., Bolvin, D., Gruber, A., Susskind, J., and Arkin, P.: The Version 2 Global Precipitation Climatology Project (GPCP) Monthly Precipitation Analysis (1979–Present), J. Hydrometeorol., 4, 1147–1167, 2003. An, Z. S.: The history and variability of the East Asian paleomonsoon climate, Quaternary Sci. Rev., 19(1–5), 171–187, 2000. Ding, Y. H.: Monsoons Over China, Springer, New York, 419 pp., 1994. Ding, Y. H.: Summer monsoon rainfalls in China, J. Meteorol. Soc. Jpn., 70(1B), 373–396, 1992. Ding, Z. L., Liu, T. S., Rutter, N. W., Yu, Z. W., Guo, Z. T., and Zhu, R. X.: Ice-volume forcing of East-Asian winter monsoon variations in the past 800,000 years, Quaternary Res., 44(2), 149–159, 1995. Guo, Q. Y. and Wang, J. Q.: Interannual variations of rain spell during predominant summer monsoon over China for recent thirty years, Acta Geogr. Sin., 36, 187–195, 1981 (in Chinese). Huang, R. H. and Wu, Y. F.: The influence of ENSO on the summer climate change in China and its mechanism, Adv. Atmos. Sci., 6, 21–32, 1989. Kanamitsu, M., Ebisuzaki, W., Woollen, J., Yang, S. K., Hnilo, J. J., Fiorino, M., and Potter, G. L.: NCEP-DOE AMIP-II reanalysis (R-2), B Am. Meteorol. Soc., 83(11), 1631–1643, 2002. Kitoh, A.: Effects of large-scale mountains on surface climate – a coupled ocean-atmosphere general circulation model study, J. Meteorol. Soc. Jpn., 80, 1165–1181, 2002. Kosaka, Y. and Nakamura, H.: Structure and dynamics of the summertime pacific-Japan teleconnection pattern, Q. J. Roy. Meteor. Soc., 132, 2009–2030, 2006. Lee, E. J., Jhun, J. G., and Park, C. K.: Remote connection of the northeast Asian summer rainfall revealed by a newly defined monsoon index, J. Climate, 18, 4381–4393, 2005. LinHo and Wang, B.:~ The time-space structure of the Asian-Pacific summer monsoon: A fast annual cycle view, J. Climate, 15, 2001–2019, 2002. Murakami, T. and Matsumoto, J.: Summer monsoon over the Asian continent and western north Pacific, J. Meteorol. Soc. Jpn., 72(5), 719–745, 1994. Nitta, T.: Convective activities in the tropical western Pacific and their impact on the Northern-Hemisphere summer circulation, J. Meteorol. Soc. Jpn., 65(3), 373–390, 1987. North, G. R., Bell, T. L., Cahalan, R. F., and Moeng, F. J.: Sampling errors in the estimation of empirical orthogonal functions, Mon. Weather Rev., 110(7), 699–706, 1982. Smith, T. M. and Reynolds, R. W.: Improved extended reconstruction of SST (1854–1997), J. Climate, 17(12), 2466–2477, 2004. Tao, S. Y. and Chen, L.: A review of recent research on East Asian summer monsoon in China, in: Monsoon Meterology, edited by: Chang, C. P. and Krishnamurti, T. N., Oxford University Press, London, 60–92, 1987. Tu, C. W. and Huang, S. S.: The advance and withdrawal of Chinese summer monsoon, Acta Meteor. Sin., 18, 81–92, 1944 (in Chinese). Wallace, J. M. and Gutzler, D. S.: Teleconnections in the geopotential height field during the northern Hemisphere winter, Mon. Weather Rev., 109(4), 784–812, 1981. Wang, B. and LinHo: Rainy season of the Asian-Pacific summer monsoon, J. Climate, 15(4), 386–398, 2002. Wang, B. and Xu, X.: Northern Hemisphere summer monsoon singularities and climatological intraseasonal oscillation, J. Climate, 10, 1071–1085, 1997. Wang, B. and Zhang, Q.: Pacific-East Asian teleconnection, part II: How the Philippine Sea anticyclone established during development of El Nino, J. Climate, 15, 3252–3265, 2002. Wang, B., Wu, R. G., and Fu, X. H.: Pacific-East Asian teleconnection: how does ENSO affect East Asian climate?, J. Climate, 13(9), 1517–1536, 2000. Wang, B., Wu, Z. W., Li, J. P., Liu, J., Chang, C. P., Ding, Y. H., and Wu, G. X.: How to Measure the Strength of the East Asian Summer Monsoon?, J. Climate, 21, 4449–4463, doi:10.1175/2008JCLI2183.1, 2008. Wang, B.: The vertical structure and development of the ENSO anomaly mode during 1979–1989, J. Atmos. Sci., 49(8), 698–712, 1992. Wang, Y. J., Cheng, H., Edwards, R. L., An, Z. S., Wu, J. Y., Shen, C. C., and Dorale, J. A.: A high-resolution absolute-dated Late Pleistocene monsoon record from Hulu Cave, China, Science, 294(5550), 2345–2348, 2001. Wu, G. X., Liu, Y. M., Liu, X., Duan, A. M., and Liang, X. Y.: How the heating over the TP affects the Asian climate in Summer, Chin., J. Atmos. Sci., 29, 47–56, 2005. Wu, R. G. and Wang, B.: Interannual variability of summer monsoon onset over the western North Pacific and the underlying processes, J. Climate, 13(14), 2483–2501, 2000. Yancheva, G., Nowaczyk, N. R., Mingram, J., Dulski, P., Schettler, G., Negendank, J. F., W., Liu, J. Q., Sigman, D. M., Peterson, L. C., and Haug, G. H.: Influence of the intertropical convergence zone on the East Asian monsoon, Nature, 445(7123), 74–77, 2007. Zhang, R. H., Sumi, A., and Kimoto, M.: Impact of El Nino on the East Asian monsoon: A diagnostic study of the '86/87 and '91/92 events, J. Meteorol. Soc. Jpn., 74(1), 49–62, 1996. Zhou, T. J. and Yu, R. C.: Atmospheric water vapor transport associated with typical anomalous summer rainfall patterns in China, J. Geophys. Res., 110, D08104, doi:10.1029/2004JD005413, 2005. Zhu, Q. G., He, J. H., and Wang, P. X.: A study of circulation differences between east-Asian and Indian summer monsoons with their interaction, Adv. Atmos. Sci., 3(4), 466–477, 1986.