• Bhalme, H. N., and D. A. Mooley, 1980: Large-scale drought/floods and monsoon circulation. Mon. Wea. Rev., 108 , 11971211.

  • Chen, T-C., and M-C. Yen, 1994: Interannual variation of the Indian monsoon simulated by the NCAR community climate model: Effect of the tropical Pacific SST. J. Climate, 7 , 14031415.

    • Search Google Scholar
    • Export Citation
  • Goswami, B. N., 1998: Interannual variations of Indian summer monsoon in a GCM: External conditions versus internal feedbacks. J. Climate, 11 , 501522.

    • Search Google Scholar
    • Export Citation
  • Hsu, H. H., C. T. Terng, and C. T. Chen, 1999: Evolution of large scale circulation and heating during the first transition of Asian summer monsoon. J. Climate, 12 , 793810.

    • Search Google Scholar
    • Export Citation
  • Joseph, P. V., J. K. Eischeid, and R. J. Pyle, 1994: Interannual variability of the onset of the Indian summer monsoon and its association with atmospheric features, El Niño, and sea surface temperature anomalies. J. Climate, 7 , 81105.

    • Search Google Scholar
    • Export Citation
  • Ju, J., and J. Slingo, 1995: The Asian summer monsoon and ENSO. Quart. J. Roy. Meteor. Soc., 121 , 11331168.

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437471.

  • Kang, I. S., C. H. Ho, Y. K. Lim, and K-M. Lau, 1999: Principal modes of climatological seasonal and intraseasonal variation of the Asian summer monsoon. Mon. Wea. Rev., 127 , 322340.

    • Search Google Scholar
    • Export Citation
  • Kawamura, R., T. Matsuura, and S. Iizuka, 2001: Interannual atmosphere-ocean variations in the tropical western north Pacific relevant to the Asian summer monsoon-ENSO coupling. J. Meteor. Soc. Japan, 79 , 883898.

    • Search Google Scholar
    • Export Citation
  • Kim, K. Y., and G. North, 1997: EOFs of harmonizable cyclostationary processes. J. Atmos. Sci., 54 , 24162427.

  • Kim, K. Y., and Q. Wu, 1999: A comparison study of EOF techniques: Analysis of nonstationary data with periodic statistics. J. Climate, 12 , 185199.

    • Search Google Scholar
    • Export Citation
  • Krishnamurthy, V., and J. Shukla, 2000: Intraseasonal and interannual variability of rainfall over India. J. Climate, 13 , 43664377.

  • Krishnamurti, T. N., P. Ardanuy, Y. Ramanathan, and R. Pasch, 1981: On the onset vortex of the summer monsoon. Mon. Wea. Rev., 109 , 344363.

    • Search Google Scholar
    • Export Citation
  • Lau, N-C., and M. J. Nath, 2000: Impact of ENSO on the variability of the Asian–Australian monsoons as simulated in GCM experiments. J. Climate, 13 , 42874309.

    • Search Google Scholar
    • Export Citation
  • Lau, N-C., and H. T. Wu, 2001: Principal modes of rainfall-SST variability of the Asian summer monsoon: A reassessment of the monsoon–ENSO relationship. J. Climate, 14 , 28802895.

    • Search Google Scholar
    • Export Citation
  • Lau, N-C., and M. J. Nath, 2003: Atmosphere–ocean variations in the Indo-Pacific sector during ENSO episodes. J. Climate, 16 , 320.

  • Lau, N-C., G. T. Yang, and S. H. Shen, 1988: Seasonal and intraseasonal climatology of summer monsoon rainfall over East Asia. Mon. Wea. Rev., 116 , 1837.

    • 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.

    • Search Google Scholar
    • Export Citation
  • Lim, Y-K., K-Y. Kim, and H-S. Lee, 2002: Temporal and spatial evolution of the Asian summer monsoon in the seasonal cycle of synoptic fields. J. Climate, 15 , 36303644.

    • Search Google Scholar
    • Export Citation
  • Madden, R. A., and P. R. Julian, 1972: Description of global-scale circulation cells in the Tropics with a 40–50 day period. J. Atmos. Sci., 29 , 11091123.

    • Search Google Scholar
    • Export Citation
  • Meehl, G. A., and J. M. Arblaster, 1998: The Asian–Australian monsoon and El Niño–Southern Oscillation in the NCAR climate system model. J. Climate, 11 , 13561385.

    • Search Google Scholar
    • Export Citation
  • Nigam, S., 1994: On the dynamical basis for the Asian summer monsoon rainfall–El Niño relationship. J. Climate, 7 , 17501771.

  • Philander, S. G. H., 1990: El Niño, La Niña, and the Southern Oscillation. 1st ed. Academic Press, 293 pp.

  • Rasmusson, E. M., and T. H. Carpenter, 1983: The relationship between eastern equatorial Pacific sea surface temperatures and rainfall over India and Sri Lanka. Mon. Wea. Rev., 111 , 517528.

    • Search Google Scholar
    • Export Citation
  • Seo, K-H., and K-Y. Kim, 2003: Propagation and initiation mechanisms of the Madden-Julian oscillation. J. Geophys. Res., 108 .4384, doi:10.1029/2002JD002876.

    • Search Google Scholar
    • Export Citation
  • Shukla, J., and D. A. Paolino, 1983: The Southern Oscillation and long-range forecasting of the summer monsoon rainfall over India. Mon. Wea. Rev., 111 , 18301837.

    • Search Google Scholar
    • Export Citation
  • Slingo, J. M., and H. Annamalai, 2000: 1997: The El Niño of the century and the response of the Indian summer monsoon. Mon. Wea. Rev., 128 , 17781797.

    • Search Google Scholar
    • Export Citation
  • Sperber, K. R., 2003: Propagation and the vertical structure of the Madden–Julian Oscillation. Mon. Wea. Rev., 131 , 30183037.

  • Torrence, C., and P. J. Webster, 1999: Interdecadal changes in the ENSO–monsoon system. J. Climate, 12 , 26792690.

  • Wang, B., and LinHo, 2002: Rainy season of the Asian–Pacific summer monsoon. J. Climate, 15 , 386398.

  • Wang, B., R. Wu, and X. Fu, 2000: Pacific–East Asian teleconnection: How does ENSO affect East Asian climate? J. Climate, 13 , 15171536.

    • 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.

    • Search Google Scholar
    • Export Citation
  • Weare, B. C., and J. N. Nasstrom, 1982: Examples of extended empirical orthogonal function analysis. Mon. Wea. Rev., 110 , 481485.

  • Webster, P. J., and S. Yang, 1992: Monsoon and ENSO; Selectively interactive systems. Quart. J. Roy. Meteor. Soc., 118 , 877926.

  • Wu, R., Z-Z. Hu, and B. P. Kirtman, 2003: Evolution of ENSO-related rainfall anomalies in east Asia. J. Climate, 16 , 37423758.

  • Xie, P., and P. A. Arkin, 1996: Analyses of global monthly precipitation using gauge observations, satellite estimates, and numerical model predictions. J. Climate, 9 , 840858.

    • Search Google Scholar
    • Export Citation
  • Yanai, M., C. Li, and Z. Song, 1992: Seasonal heating of the Tibetan Plateau and its effects on the evolution of the Asian summer monsoon. J. Meteor. Soc. Japan, 70 , 1B. 319351.

    • Search Google Scholar
    • Export Citation
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ENSO Impact on the Space–Time Evolution of the Regional Asian Summer Monsoons

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  • 1 Center for Ocean–Atmospheric Prediction Studies, The Florida State University, Tallahassee, Florida
  • | 2 Department of Meteorology, The Florida State University, Tallahassee, Florida
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Abstract

This study investigates how ENSO affects the space–time evolution of the Asian summer monsoon (ASM) precipitation and synoptic variables on a 5-day resolution over the entire ASM area. Cyclostationary EOF and regression methods were used to investigate the detailed evolution features associated with ENSO during the prominent life cycle of the ASM (21 May–17 September). This ENSO mode is identified as the third largest component (next to the seasonal cycle and the intraseasonal oscillations with a 40–50-day period) of the ASM rainfall variation.

The ENSO mode reveals that the individual regional monsoons over the ASM domain respond to ENSO in a complex manner. 1) Under the El Niño condition, the early monsoon stage over India, the Bay of Bengal, and the Indochina peninsula is characterized by rainfall deficit, along with a delayed monsoon onset by one or two pentads. This is the result of weakened diabatic heating over the Asian continent and meridional pressure gradient over the Indian Ocean, causing a weak low-tropospheric westerly monsoonal flow and the ensuing moisture transport decrease toward the regional monsoon areas. Onsets of the subsequent regional monsoons are delayed successively by this poorly developed ASM system in the early stage. 2) The Walker circulation anomaly persistently induces an enhanced subsidence over the Maritime Continent, resulting in a drought condition over this region for the entire ASM period. 3) The Hadley circulation anomaly linked to the Walker circulation anomaly over the Tropics drives a rising motion over the subtropical western Pacific, resulting in a wetter south China monsoon. The negative sea level pressure anomaly over the subtropical western Pacific associated with this anomalous Hadley circulation provides an unfavorable condition for the moisture transport toward East Asia, causing drier monsoons over north China, Japan, and Korea regions. 4) This negative sea level pressure anomaly intrudes into India, the Bay of Bengal, and the Indochina peninsula during late July and early August, developing a brief wet period over these regions. In contrast, the physical changes including the onset variation and the monsoon strength addressed above are reversed during La Niña events.

In reality, the observed ASM rainfall anomaly does not necessarily follow the ENSO-related patterns addressed above because of other impacts contributing to the rainfall variations. Although the impact of ENSO is moderately important, a comparison with other impacts demonstrates that the rainfall variations are controlled more by regional-scale intraseasonal oscillations.

* Current affiliation: Environmental Forecasts and Value-Oriented Research, Inc., Tallahassee, Florida

Corresponding author address: Kwang-Yul Kim, Department of Meteorology, The Florida State University, 404 Love Bldg., Tallahassee, FL 32306-4250. Email: kwang56@gmail.com

Abstract

This study investigates how ENSO affects the space–time evolution of the Asian summer monsoon (ASM) precipitation and synoptic variables on a 5-day resolution over the entire ASM area. Cyclostationary EOF and regression methods were used to investigate the detailed evolution features associated with ENSO during the prominent life cycle of the ASM (21 May–17 September). This ENSO mode is identified as the third largest component (next to the seasonal cycle and the intraseasonal oscillations with a 40–50-day period) of the ASM rainfall variation.

The ENSO mode reveals that the individual regional monsoons over the ASM domain respond to ENSO in a complex manner. 1) Under the El Niño condition, the early monsoon stage over India, the Bay of Bengal, and the Indochina peninsula is characterized by rainfall deficit, along with a delayed monsoon onset by one or two pentads. This is the result of weakened diabatic heating over the Asian continent and meridional pressure gradient over the Indian Ocean, causing a weak low-tropospheric westerly monsoonal flow and the ensuing moisture transport decrease toward the regional monsoon areas. Onsets of the subsequent regional monsoons are delayed successively by this poorly developed ASM system in the early stage. 2) The Walker circulation anomaly persistently induces an enhanced subsidence over the Maritime Continent, resulting in a drought condition over this region for the entire ASM period. 3) The Hadley circulation anomaly linked to the Walker circulation anomaly over the Tropics drives a rising motion over the subtropical western Pacific, resulting in a wetter south China monsoon. The negative sea level pressure anomaly over the subtropical western Pacific associated with this anomalous Hadley circulation provides an unfavorable condition for the moisture transport toward East Asia, causing drier monsoons over north China, Japan, and Korea regions. 4) This negative sea level pressure anomaly intrudes into India, the Bay of Bengal, and the Indochina peninsula during late July and early August, developing a brief wet period over these regions. In contrast, the physical changes including the onset variation and the monsoon strength addressed above are reversed during La Niña events.

In reality, the observed ASM rainfall anomaly does not necessarily follow the ENSO-related patterns addressed above because of other impacts contributing to the rainfall variations. Although the impact of ENSO is moderately important, a comparison with other impacts demonstrates that the rainfall variations are controlled more by regional-scale intraseasonal oscillations.

* Current affiliation: Environmental Forecasts and Value-Oriented Research, Inc., Tallahassee, Florida

Corresponding author address: Kwang-Yul Kim, Department of Meteorology, The Florida State University, 404 Love Bldg., Tallahassee, FL 32306-4250. Email: kwang56@gmail.com

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