• Chang, C.-P., , Y. Zhang, , and T. Li, 2000: Interannual and interdecadal variations of the East Asian summer monsoon and tropical Pacific SSTs. Part I: Roles of the subtropical ridge. J. Climate, 13, 43104325, doi:10.1175/1520-0442(2000)013<4310:IAIVOT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chen, L., , M. Dong, , and Y. N. Shao, 1992: The characteristics of interannual variations on the East Asian monsoon. J. Meteor. Soc. Japan, 70, 397421.

    • Search Google Scholar
    • Export Citation
  • Chen, M., , P. Xie, , J. E. Janowiak, , and P. A. Arkin, 2002: Global land precipitation: A 50-yr monthly analysis based on gauge observations. J. Hydrometeor., 3, 249266, doi:10.1175/1525-7541(2002)003<0249:GLPAYM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chen, T.-J. G., , and C.-P. Chang, 1980: The structure and vorticity budget of an early summer monsoon trough (mei-yu) over southeastern China and Japan. Mon. Wea. Rev., 108, 942953, doi:10.1175/1520-0493(1980)108<0942:TSAVBO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chen, Z., , R. G. Wu, , and W. Chen, 2014: Distinguishing interannual variations of the northern and southern modes of the East Asian winter monsoon. J. Climate, 27, 835851, doi:10.1175/JCLI-D-13-00314.1.

    • Search Google Scholar
    • Export Citation
  • Chu, J.-E., , S. N. Hameed, , and K.-J. Ha, 2012: Nonlinear, intraseasonal phases of the East Asian summer monsoon: Extraction and analysis using self-organizing maps. J. Climate, 25, 69756988, doi:10.1175/JCLI-D-11-00512.1.

    • Search Google Scholar
    • Export Citation
  • Collins, W. D., and et al. , 2006: The Community Climate System Model version 3 (CCSM3). J. Climate, 19, 21222143, doi:10.1175/JCLI3761.1.

    • Search Google Scholar
    • Export Citation
  • Dai, A., , H. Li, , Y. Sun, , L. Hong, , LinHo, , C. Chou, , and T. J. Zhou, 2013: The relative roles of upper and lower tropospheric thermal contrasts and tropical influences in driving Asian summer monsoons. J. Geophys. Res. Atmos., 118, 70247045, doi:10.1002/jgrd.50565.

    • Search Google Scholar
    • Export Citation
  • Dai, N., , A. Xie, , and Y. Zhang, 2000: Interannual and interdecadal variations of summer monsoon activities over South China Sea. Climate Environ. Res., 5, 363374.

    • Search Google Scholar
    • Export Citation
  • Ding, R., , K.-J. Ha, , and J. Li, 2010: Interdecadal shift in the relationship between the East Asian summer monsoon and the tropical Indian Ocean. Climate Dyn., 34, 10591071, doi:10.1007/s00382-009-0555-2.

    • Search Google Scholar
    • Export Citation
  • Doblas-Reyes, F. J., and et al. , 2009: Addressing model uncertainty in seasonal and annual dynamical ensemble forecasts. Quart. J. Roy. Meteor. Soc., 135, 15381559, doi:10.1002/qj.464.

    • Search Google Scholar
    • Export Citation
  • Du, Y., , Y. Zhang, , and Z. Xie, 2008: Impacts of longitude location changes of East Asian westerly jet core on the precipitation distribution during meiyu period in middle-lower reaches of Yangtze River valley. Acta Meteor. Sin., 66, 566576.

    • Search Google Scholar
    • Export Citation
  • Guo, Q., 1983: The summer monsoon intensity index in East Asia and its variation (in Chinese). Acta Geogr. Sin., 38, 207217.

  • Ha, K.-J., , S.-K. Park, , and K.-Y. Kim, 2005: On interannual characteristics of Climate Prediction Center merged analysis precipitation over the Korean peninsula during the summer monsoon season. Int. J. Climatol., 25, 99116, doi:10.1002/joc.1116.

    • Search Google Scholar
    • Export Citation
  • He, J., , J. Ju, , Z. Wen, , J. Lu, , and Q. Jin, 2007: A review of recent advances in research on Asian monsoon in China. Adv. Atmos. Sci., 24, 972992, doi:10.1007/s00376-007-0972-2.

    • Search Google Scholar
    • Export Citation
  • Hirota, N., , and M. Takahashi, 2012: A tripolar pattern as an internal mode of the East Asian summer monsoon. Climate Dyn., 39, 22192238, doi:10.1007/s00382-012-1416-y.

    • Search Google Scholar
    • Export Citation
  • Hsu, H.-H., , T. Zhou, , and J. Matsumoto, 2014: East Asian, Indochina and western north Pacific summer monsoon—An update. Asia-Pac. J. Atmos. Sci., 50, 4568, doi:10.1007/s13143-014-0027-4.

    • Search Google Scholar
    • Export Citation
  • Hu, K., , G. Huang, , and R. Huang, 2011: The impact of tropical Indian Ocean variability on summer surface air temperature in China. J. Climate, 24, 53655377, doi:10.1175/2011JCLI4152.1.

    • Search Google Scholar
    • Export Citation
  • Hu, K., , G. Huang, , and R. Wu, 2013: A strengthened influence of ENSO on August high temperature extremes over the southern Yangtze River valley since the late 1980s. J. Climate, 26, 22052221, doi:10.1175/JCLI-D-12-00277.1.

    • Search Google Scholar
    • Export Citation
  • Hu, K., , G. Huang, , X.-T. Zheng, , S. P. Xie, , X. Qu, , Y. Du, , and L. Liu, 2014: Interdecadal variations in ENSO influences on northwest Pacific–East Asian early summertime climate simulated in CMIP5 models. J. Climate, 27, 59825998, doi:10.1175/JCLI-D-13-00268.1.

    • Search Google Scholar
    • Export Citation
  • Huang, G., , and Z. Yan, 1999: The East Asian summer monsoon circulation anomaly index and its interannual variations. Chin. Sci. Bull., 44, 13251329, doi:10.1007/BF02885855.

    • Search Google Scholar
    • Export Citation
  • Huang, G., , K. Hu, , and S.-P. Xie, 2010: Strengthening of tropical Indian Ocean teleconnection to the northwest Pacific since the mid-1970s: An atmospheric GCM study. J. Climate, 23, 52945304, doi:10.1175/2010JCLI3577.1.

    • Search Google Scholar
    • Export Citation
  • Huang, R., , and Y. Wu, 1989: The influence of ENSO on the summer climate change in China and its mechanism. Adv. Atmos. Sci., 6, 2132, doi:10.1007/BF02656915.

    • Search Google Scholar
    • Export Citation
  • Huang, R., , J. Chen, , L. Wang, , and Z. Lin, 2012: Characteristics, processes, and causes of the spatio-temporal variabilities of the East Asian monsoon system. Adv. Atmos. Sci., 29, 910942, doi:10.1007/s00376-012-2015-x.

    • Search Google Scholar
    • Export Citation
  • Jiang, D., , and H. Wang, 2005: Natural interdecadal weakening of East Asian summer monsoon in the late 20th century. Chin. Sci. Bull., 50, 19231929, doi:10.1360/982005-36.

    • Search Google Scholar
    • Export Citation
  • Jiang, T., , Z. W. Kundzewicz, , and B. Su, 2008: Changes in monthly precipitation and flood hazard in the Yangtze River basin, China. Int. J. Climatol., 28, 14711481, doi:10.1002/joc.1635.

    • Search Google Scholar
    • Export Citation
  • Kim, B.-H., , and K.-J. Ha, 2015: Observed changes of global and western Pacific precipitation associated with global warming SST mode and mega-ENSO SST mode. Climate Dyn., doi:10.1007/s00382-015-2524-2, in press.

    • Search Google Scholar
    • Export Citation
  • Kobayashi, S., and et al. , 2015: The JRA-55 Reanalysis: General specifications and basic characteristics. J. Meteor. Soc. Japan, 93, 548, doi:10.2151/jmsj.2015-001.

    • Search Google Scholar
    • Export Citation
  • Kosaka, Y., , and H. Nakamura, 2010: Mechanisms of meridional teleconnection observed between a summer monsoon system and a subtropical anticyclone. Part I: The Pacific–Japan pattern. J. Climate, 23, 50855108, doi:10.1175/2010JCLI3413.1.

    • Search Google Scholar
    • Export Citation
  • Kwon, M., , J.-G. Jhun, , and K.-J. Ha, 2007: Decadal change in East Asian summer monsoon circulation in the mid-1990s. Geophys. Res. Lett., 34, L21706, doi:10.1029/2007GL031977.

    • Search Google Scholar
    • Export Citation
  • Lau, K.-M., , and M.-T. Li, 1984: The monsoon of East Asia and its global associations—A survey. Bull. Amer. Meteor. Soc., 65, 114125, doi:10.1175/1520-0477(1984)065<0114:TMOEAA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Lau, K.-M., , K.-M. Kim, , and S. Yang, 2000: Dynamical and boundary forcing characteristics of regional components of the Asian summer monsoon. J. Climate, 13, 24612482, doi:10.1175/1520-0442(2000)013<2461:DABFCO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Lee, E.-J., , J.-G. Jhun, , and C.-K. Park, 2005: Remote connection of the northeast Asian summer rainfall variation revealed by a newly defined monsoon index. J. Climate, 18, 43814393, doi:10.1175/JCLI3545.1.

    • Search Google Scholar
    • Export Citation
  • Li, C., , and M. Yanai, 1996: The onset and interannual variability of the Asian summer monsoon in relation to land–sea thermal contrast. J. Climate, 9, 358375, doi:10.1175/1520-0442(1996)009<0358:TOAIVO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Li, C., , J. Wang, , S. Lin, , and H. Cho, 2004: The relationship between East Asian summer monsoon activity and northward jump of the upper westerly jet location (in Chinese). Chin. J. Atmos. Sci., 28, 641658.

    • Search Google Scholar
    • Export Citation
  • Li, C. F., , R. Lu, , and B. Dong, 2012: Predictability of the western North Pacific summer climate demonstrated by the coupled models of ENSEMBLES. Climate Dyn., 39, 329346, doi:10.1007/s00382-011-1274-z.

    • Search Google Scholar
    • Export Citation
  • Li, Y., , J. Li, , and J. Feng, 2013: Boreal summer convection oscillation over the Indo-western Pacific and its relationship with the East Asian summer monsoon. Atmos. Sci. Lett., 14, 6671, doi:10.1002/asl2.418.

    • Search Google Scholar
    • Export Citation
  • Liang, X.-Z., , and W.-C. Wang, 1998: Associations between China monsoon rainfall and tropospheric jets. Quart. J. Roy. Meteor. Soc., 124, 25972623, doi:10.1002/qj.49712455204.

    • Search Google Scholar
    • Export Citation
  • Lin, Z., , and R. Lu, 2009: The ENSO’s effect on eastern China rainfall in the following early summer. Adv. Atmos. Sci., 26, 333342, doi:10.1007/s00376-009-0333-4.

    • Search Google Scholar
    • Export Citation
  • Liu, H., , T. Zhou, , Y. Zhu, , and Y. Lin, 2012: The strengthening East Asia summer monsoon since the early 1990s. Chin. Sci. Bull., 57, 15531558, doi:10.1007/s11434-012-4991-8.

    • Search Google Scholar
    • Export Citation
  • Murakami, T., , and J. Matsumoto, 1994: Summer monsoon over the Asian continent and western north Pacific. J. Meteor. Soc. Japan, 72, 719745.

    • Search Google Scholar
    • Export Citation
  • Nitta, T., 1987: Convective activities in the tropical western Pacific and their impact on the Northern Hemisphere summer circulation. J. Meteor. Soc. Japan, 65, 373390.

    • Search Google Scholar
    • Export Citation
  • Oh, H., , and K.-J. Ha, 2015: Thermodynamic characteristics and responses to ENSO of dominant intraseasonal modes in the East Asian summer monsoon. Climate Dyn., 44, 17511766, doi:10.1007/s00382-014-2268-4.

    • Search Google Scholar
    • Export Citation
  • Peixóto, J. P., , and A. H. Oort, 1984: Physics of climate. Rev. Mod. Phys., 56, 365, http://dx.doi.org/10.1103/RevModPhys.56.365.

  • Peng, J., , Z. Sun, , and D. Ni, 2000: Relation of eastern Asian summer monsoon with the equatorial eastern Pacific spring SSTA (in Chinese). J. Nanjing Inst. Meteor., 23, 385390.

    • Search Google Scholar
    • Export Citation
  • Qian, Y., , D. Gong, , J. Fan, , L. R. Leung, , R. Bennartz, , D. Chen, , and W. Wang, 2009: Heavy pollution suppresses light rain in China: Observations and modeling. J. Geophys. Res., 114, D00K02, doi:10.1029/2008JD011575.

    • Search Google Scholar
    • Export Citation
  • Qu, X., , and G. Huang, 2012: Impacts of tropical Indian Ocean SST on the meridional displacement of East Asian jet in boreal summer. Int. J. Climatol., 32, 20732080, doi:10.1002/joc.2378.

    • Search Google Scholar
    • Export Citation
  • Rodwell, M. J., , and B. J. Hoskins, 2001: Subtropical anticyclones and summer monsoons. J. Climate, 14, 31923211, doi:10.1175/1520-0442(2001)014<3192:SAASM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Sampe, T., , and S.-P. Xie, 2010: Large-scale dynamics of the meiyu-baiu rainband: Environmental forcing by the westerly jet. J. Climate, 23, 113134, doi:10.1175/2009JCLI3128.1.

    • Search Google Scholar
    • Export Citation
  • Shen, S., , and K.-M. Lau, 1995: Biennial oscillation associated with the East-Asian summer monsoon and tropical sea-surface temperatures. J. Meteor. Soc. Japan, 73, 105124.

    • Search Google Scholar
    • Export Citation
  • Shi, N., , and Q. G. Zhu, 1996: An abrupt change in the intensity of the East Asian summer monsoon index and its relationship with temperature and precipitation over east China. Int. J. Climatol., 16, 757764, doi:10.1002/(SICI)1097-0088(199607)16:7<757::AID-JOC50>3.0.CO;2-5.

    • Search Google Scholar
    • Export Citation
  • Smith, T. M., , R. W. Reynolds, , T. C. Peterson, , and J. Lawrimore, 2007: Improvements to NOAA's historical merged land–ocean surface temperature analysis (1880–2006). J. Climate, 21, 22832296, doi:10.1175/2007JCLI2100.1.

    • Search Google Scholar
    • Export Citation
  • Song, F., , T. Zhou, , and Y. Qian, 2014: Responses of East Asian summer monsoon to natural and anthropogenic forcings in the 17 latest CMIP5 models. Geophys. Res. Lett., 41, 596603, doi:10.1002/2013GL058705.

    • Search Google Scholar
    • Export Citation
  • Tao, S., , and L. Chen, 1957: The structure of general circulation over continent of Asia in summer. Acta Meteor. Sin., 28, 234247.

  • Tao, S., , and J. Wei, 2006: The westward and northward advance of the subtropical high over the west Pacific in summer (in Chinese). J. Appl. Meteor. Sci., 17, 513525.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , and Z. Fan, 1999: Choice of South Asian summer monsoon indices. Bull. Amer. Meteor. Soc., 80, 629638, doi:10.1175/1520-0477(1999)080<0629:COSASM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , R. Wu, , and X. Fu, 2000: Pacific–East Asian teleconnection: How does ENSO affect East Asian climate? J. Climate, 13, 15171536, doi:10.1175/1520-0442(2000)013<1517:PEATHD>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , R. Wu, , and K.-M. Lau, 2001: Interannual variability of the Asian summer monsoon: Contrasts between the Indian and the western north Pacific–East Asian monsoons. J. Climate, 14, 40734090, doi:10.1175/1520-0442(2001)014<4073:IVOTAS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , Z. Wu, , J. Li, , J. Liu, , C.-P. Chang, , Y. Ding, , and G. Wu, 2008: How to measure the strength of the East Asian summer monsoon. J. Climate, 21, 44494463, doi:10.1175/2008JCLI2183.1.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , J. Liu, , J. Yang, , T. Zhou, , and Z. W. Wu, 2009: Distinct principal modes of early and late summer rainfall anomalies in East Asia. J. Climate, 22, 38643875, doi:10.1175/2009JCLI2850.1.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , Z. Wu, , C.-P. Chang, , J. Liu, , J. Li, , and T. Zhou, 2010: Another look at interannual-to-interdecadal variations of the East Asian winter monsoon: The northern and southern temperature modes. J. Climate, 23, 14951512, doi:10.1175/2009JCLI3243.1.

    • Search Google Scholar
    • Export Citation
  • Wang, Y., , B. Wang, , and J.-H. Oh, 2001: Impact of the preceding El Nino on the East Asian summer atmosphere circulation. J. Meteor. Soc. Japan, 79, 575588, doi:10.2151/jmsj.79.575.

    • Search Google Scholar
    • Export Citation
  • Webster, P. J., , and S. Yang, 1992: Monsoon and ENSO: Selectively interactive systems. Quart. J. Roy. Meteor. Soc., 118, 877926, doi:10.1002/qj.49711850705.

    • Search Google Scholar
    • Export Citation
  • Wu, A., , and Y. Ni, 1997: The influence of Tibetan Plateau on the interannual variability of Asian monsoon. Adv. Atmos. Sci., 14, 491504, doi:10.1007/s00376-997-0067-0.

    • Search Google Scholar
    • Export Citation
  • Wu, B., , R. Zhang, , Y. Ding, , and R. D’Arrigo, 2008: Distinct modes of the East Asian summer monsoon. J. Climate, 21, 11221138, doi:10.1175/2007JCLI1592.1.

    • Search Google Scholar
    • Export Citation
  • Wu, R., , J. Chen, , and Z. Wen, 2013: Precipitation–surface temperature relationship in the IPCC CMIP5 models. Adv. Atmos. Sci., 30, 766778, doi:10.1007/s00376-012-2130-8.

    • Search Google Scholar
    • Export Citation
  • Wu, Z., , J. Li, , Z. Jiang, , J. He, , and X. Zhu, 2012: Possible effects of the North Atlantic Oscillation on the strengthening relationship between the East Asian summer monsoon and ENSO. Int. J. Climatol., 32, 794800, doi:10.1002/joc.2309.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., , K. Hu, , J. Hafner, , H. Tokinaga, , Y. Du, , G. Huang, , and T. Sampe, 2009: Indian Ocean capacitor effect on Indo–western Pacific climate during the summer following El Niño. J. Climate, 22, 730747, doi:10.1175/2008JCLI2544.1.

    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., , Y. Du, , G. Huang, , X.-T. Zheng, , H. Tokinaga, , K. Hu, , and Q. Liu, 2010: Decadal shift in El Niño influences on Indo-western Pacific and East Asian climate in the 1970s. J. Climate, 23, 33523368, doi:10.1175/2010JCLI3429.1.

    • Search Google Scholar
    • Export Citation
  • Yang, S., , and P. J. Webster, 1990: The effect of summer tropical heating on the location and intensity of the extratropical westerly jet streams. J. Geophys. Res., 95, 18 70518 721, doi:10.1029/JD095iD11p18705.

    • Search Google Scholar
    • Export Citation
  • Yun, K.-S., , K.-H. Seo, , and K.-J. Ha, 2008: Relationship between ENSO and northward propagating intraseasonal oscillation in the East Asian summer monsoon system. J. Geophys. Res., 113, D14120, doi:10.1029/2008JD009901.

    • Search Google Scholar
    • Export Citation
  • Yun, K.-S., , K.-H. Seo, , and K.-J. Ha, 2010: Interdecadal change in the relationship between ENSO and the intraseasonal oscillation in East Asia. J. Climate, 23, 35993612, doi:10.1175/2010JCLI3431.1.

    • Search Google Scholar
    • Export Citation
  • Zhang, Q., , S. Tao, , and L. Chen, 2003: The inter-annual variability of East Asian summer monsoon indices and its association with the pattern of general circulation over East Asia (in Chinese). Acta Meteor. Sin., 61, 559568.

    • Search Google Scholar
    • Export Citation
  • Zhang, Y., , and X. Kuang, 2006: Simulation of seasonal variation of the East Asian subtropical westerly jet in a coupled climate system model FGCM0. Chin. J. Atmos. Sci., 30, 11771188.

    • Search Google Scholar
    • Export Citation
  • Zhang, Y., , X. Kuang, , W. Guo, , and T. Zhou, 2006: Seasonal evolution of the upper-tropospheric westerly jet core over East Asia. Geophys. Res. Lett., 33, L11708, doi:10.1029/2006GL026377.

    • Search Google Scholar
    • Export Citation
  • Zhao, P., , and Z. Zhou, 2009: An East Asian subtropical summer monsoon index and its relationship to summer rainfall in China. Acta Meteor. Sin., 23, 1828.

    • Search Google Scholar
    • Export Citation
  • Zhou, T., , D. Gong, , J. Li, , and B. Li, 2009: Detecting and understanding the multi-decadal variability of the East Asian summer monsoon—Recent progress and state of affairs. Meteor. Z., 18, 455467, doi:10.1127/0941-2948/2009/0396.

    • Search Google Scholar
    • Export Citation
  • Zhu, C., , H. Jinhai, , and W. Guoxiong, 2000: East Asian monsoon index and its interannual relationship with large-scale thermal dynamic circulation. Acta Meteor. Sin., 58, 391402.

    • Search Google Scholar
    • Export Citation
  • Zhu, C. W., , B. Wang, , W. H. Qian, , and B. Zhang, 2012: Recent weakening of northern East Asian summer monsoon: A possible response to global warming. Geophys. Res. Lett., 39, L09701, doi:10.1029/2012GL051155.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 129 129 35
PDF Downloads 179 179 25

A New Upper-Level Circulation Index for the East Asian Summer Monsoon Variability

View More View Less
  • 1 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, and College of Earth Science, University of Chinese Academy of Sciences, Beijing, China
  • | 2 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, and Joint Center for Global Change Studies, Beijing, China
  • | 3 Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
© Get Permissions
Restricted access

Abstract

The East Asian summer monsoon (EASM) and its variability involve circulation systems in both the tropics and midlatitudes as well as in both the lower and upper troposphere. Considering this fact, a new EASM index (NEWI) is proposed based on 200-hPa zonal wind, which takes into account wind anomalies in the southern (about 5°N), middle (about 20°N), and northern areas (about 35°N) of East Asia. The NEWI can capture the interannual EASM-related climate anomalies and the interdecadal variability well. Compared to previous indices, the NEWI shows a better performance in describing precipitation and air temperature variations over East Asia. It can also show distinct climate anomalous features in early and late summer. The NEWI is tightly associated with the East Asian–Pacific or the Pacific–Japan teleconnection, suggesting a possible role of internal dynamics in the EASM variability. Meanwhile, the NEWI is significantly linked to El Niño–Southern Oscillation and tropical Indian Ocean sea surface temperature anomalies. Furthermore, the NEWI is highly predictable in the ENSEMBLES models, indicating its advantage for operational prediction of the EASM. The physical mechanism of the EASM variability as represented by the NEWI is also explicit. Both warm advection anomalies of temperature by anomalous westerly winds and the advection of anomalous positive relative vorticity by northerly basic winds cause anomalous ascending motion over the mei-yu–changma–baiu rainfall area, and vice versa over the South China Sea area. Hence, this NEWI would be a good choice to study, monitor, and predict the EASM.

Corresponding author address: Gang Huang, State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. E-mail: hg@mail.iap.ac.cn.

Abstract

The East Asian summer monsoon (EASM) and its variability involve circulation systems in both the tropics and midlatitudes as well as in both the lower and upper troposphere. Considering this fact, a new EASM index (NEWI) is proposed based on 200-hPa zonal wind, which takes into account wind anomalies in the southern (about 5°N), middle (about 20°N), and northern areas (about 35°N) of East Asia. The NEWI can capture the interannual EASM-related climate anomalies and the interdecadal variability well. Compared to previous indices, the NEWI shows a better performance in describing precipitation and air temperature variations over East Asia. It can also show distinct climate anomalous features in early and late summer. The NEWI is tightly associated with the East Asian–Pacific or the Pacific–Japan teleconnection, suggesting a possible role of internal dynamics in the EASM variability. Meanwhile, the NEWI is significantly linked to El Niño–Southern Oscillation and tropical Indian Ocean sea surface temperature anomalies. Furthermore, the NEWI is highly predictable in the ENSEMBLES models, indicating its advantage for operational prediction of the EASM. The physical mechanism of the EASM variability as represented by the NEWI is also explicit. Both warm advection anomalies of temperature by anomalous westerly winds and the advection of anomalous positive relative vorticity by northerly basic winds cause anomalous ascending motion over the mei-yu–changma–baiu rainfall area, and vice versa over the South China Sea area. Hence, this NEWI would be a good choice to study, monitor, and predict the EASM.

Corresponding author address: Gang Huang, State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. E-mail: hg@mail.iap.ac.cn.
Save