• Chang, C.-P., S. C. Hou, H. C. Kuo, and G. T. Chen, 1998: The development of an intense East Asian summer monsoon disturbance with strong vertical coupling. Mon. Wea. Rev.,126, 2692–2712.

  • ——, Y. Zhang, and T. Li, 2000: Interannual and interdecadal variations of the East Asian summer monsoon and the tropical sea-surface temperatures. Part I: Roles of the subtropical ridge. J. Climate,13, 4310–4325.

  • Chu, P., and C.-P. Chang, 1997: South China Sea warm pool in boreal spring. Adv. Atmos. Sci.,14, 195–206.

  • ——, H. C. Tseng, C.-P. Chang, and J. M. Chen, 1997: South China Sea warm pool detected in spring from the Navy’s Master Oceanographic Observational Data Set (MOODS). J. Geophys. Res.,102 (C7), 15 761–15 771.

  • Ding, Y. H., 1992: Summer monsoon rainfalls in China. J. Meteor. Soc. Japan,70, 373–396.

  • ——, 1994: Monsoon over China. Kluwer Academic Publishers, 420 pp.

  • Huang, R., and Y. Wu, 1989: The influence of ENSO on the summer climate change in China and its mechanism. Adv. Atmos. Sci.,6, 21–32.

  • ——, and F. Sun, 1992: Impacts of the tropical western Pacific on the East Asian summer monsoon. J. Meteor. Soc. Japan,70, 243–256.

  • Johnson, R. H., Z. Wang, and J. F. Bresch, 1993: Heat and moisture budgets over China during the early summer monsoon. J. Meteor. Soc. Japan,71, 137–152.

  • Lau, K. M., and S. Yang, 1996: The Asian monsoon and predictability of the tropical ocean–atmosphere system. Quart. J. Roy. Meteor. Soc.,122, 945–957.

  • ——, and ——, 1997: Climatology and interannual variability of the Southeast Asian summer monsoon. Adv. Atmos. Sci.,14, 141–162.

  • Liu, Y., and Y. H. Ding, 1992: Influence of El Niño on weather and climate in China. Acta Meteor. Sin.,6, 117–131.

  • Meehl, G. A., 1987: The annual cycle and interannual variability in the tropical Pacific and Indian Ocean region. Mon. Wea. Rev.,115, 27–50.

  • —— 1997: The South Asian monsoon and the tropospheric biennial oscillation. J. Climate,10, 1921–1943.

  • ——, and W. M. Washington, 1996: El Niño–like climate change in a model with increased atmospheric CO2 concentrations. Nature,382, 56–60.

  • Shen, S., and K. M. Lau, 1995: Biennial oscillation associated with the East Asian monsoon and tropical sea surface temperatures. J. Meteor. Soc. Japan,73, 105–124.

  • Tian, S. F., and T. Yasunari, 1992: Time and space structure of interannual variations in summer rainfall over China. J. Meteor. Soc. Japan,70, 585–596.

  • Trenberth, K. E., and T. J. Hoar, 1996: The 1990–1995 El Niño–Southern Oscillation event: Longest on record. Geophys. Res. Lett.,23, 57–60.

  • Wang, B., 1995: Interdecadal changes in El Niño onset in the last four decades. J. Climate,8, 267–285.

  • ——, and H. Weng, 1999: Interannual, decadal-to-interdecadal, and global warming signals in sea surface temperature during 1955–97. J. Climate,12, 1257–1267.

  • Webster, P. J., V. O. Magana, T. N. Palmer, J. Shukla, R. A. Tomas, M. Yanai, and T. Yasunari, 1998: Monsoons: Processes, predictability, and the prospects for prediction. J. Geophys. Res.,103 (C7), 14 451–14 510.

  • Weng, H., K.-M. Lau, and Y. Xue, 1999: Multi-scale summer rainfall variability over China and its long-term link to global sea surface temperature variability. J. Meteor. Soc. Japan,77, 845–857.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 361 361 21
PDF Downloads 121 121 8

Interannual and Interdecadal Variations of the East Asian Summer Monsoon and Tropical Pacific SSTs. Part II: Meridional Structure of the Monsoon

View More View Less
  • 1 Department of Meteorology, Naval Postgraduate School, Monterey, California
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

The relationship between the interannual variations of the East Asian summer monsoon and that of the tropical SST shows considerable variations. In this study, rainfall in the southeastern coastal area of China (SEC) during 1951–96 is used to composite the tropical SST, 850-hPa wind, and 500-hPa height. The results relative to the May–June rainfall, which represents most of the SEC summer monsoon rainfall, are compared to the Yangtze River Valley (YRV) rainfall composites. It is shown that strong interdecadal changes in the Pacific may account for the observed variations in the meridional structure of the monsoon–SST relationship. The western Pacific 500-hPa subtropical ridge, which is influenced by the equatorial eastern Pacific SST, is crucial to these variations.

During 1951–77 the SEC wet phase is produced by an anomalous anticyclone in the northern South China Sea, which tends to make the monsoon pre-Mei-yu and Mei-yu fronts quasi-stationary in the general area of both SEC and YRV, and also helps to warm the SST in the northern South China Sea. In this case the monsoon rainfalls in the two regions are in phase.

During 1978–96 the mean equatorial eastern Pacific SST is higher, leading to a stronger and more expansive mean western Pacific subtropical ridge. Its proximity to the SEC region causes the latter to experience a strong interdecadal change, with less mean rainfall than 1951–77. Within the 1978–96 period, the anomalous anticyclone sustaining the YRV wet phase is situated near SEC, suppressing the SEC rainfall. Therefore the SEC and YRV rainfalls become out of phase.

The SEC wet phase in 1978–96 depends on an anomalous 850-hPa cyclone in the East China Sea. This anomalous cyclone, which transports moist air onshore from the east resulting in maximum moisture convergence in SEC, develops when the western Pacific subtropical ridge is weak and displaced equatorward. The flow is more baroclinic and the monsoon fronts are active in the southeast coastal area. In this case the SEC and YRV rainfalls are uncorrelated.

The July and August SEC wet phases show opposite characteristics. The wet July phase depends on anomalous 850-hPa cyclonic circulation in the northern South China Sea (and the East China Sea during 1951–77), which requires a retreat of the western edge of the western Pacific subtropical ridge. The anomalous South China Sea cyclone may be due to more frequent tropical cyclone activity. This is in contrast to the wet August phase, which is associated with anomalous anticyclones in the northern South China Sea and a greater westward extension of the subtropical ridge.

* Current affiliation: IPRC, University of Hawaii, Honolulu, Hawaii.

Corresponding author address: Dr. C.-P. Chang, Dept. of Meteorology, Naval Postgraduate School, Monterey, CA 93943.

Email: cpchang@nps.navy.mil

Abstract

The relationship between the interannual variations of the East Asian summer monsoon and that of the tropical SST shows considerable variations. In this study, rainfall in the southeastern coastal area of China (SEC) during 1951–96 is used to composite the tropical SST, 850-hPa wind, and 500-hPa height. The results relative to the May–June rainfall, which represents most of the SEC summer monsoon rainfall, are compared to the Yangtze River Valley (YRV) rainfall composites. It is shown that strong interdecadal changes in the Pacific may account for the observed variations in the meridional structure of the monsoon–SST relationship. The western Pacific 500-hPa subtropical ridge, which is influenced by the equatorial eastern Pacific SST, is crucial to these variations.

During 1951–77 the SEC wet phase is produced by an anomalous anticyclone in the northern South China Sea, which tends to make the monsoon pre-Mei-yu and Mei-yu fronts quasi-stationary in the general area of both SEC and YRV, and also helps to warm the SST in the northern South China Sea. In this case the monsoon rainfalls in the two regions are in phase.

During 1978–96 the mean equatorial eastern Pacific SST is higher, leading to a stronger and more expansive mean western Pacific subtropical ridge. Its proximity to the SEC region causes the latter to experience a strong interdecadal change, with less mean rainfall than 1951–77. Within the 1978–96 period, the anomalous anticyclone sustaining the YRV wet phase is situated near SEC, suppressing the SEC rainfall. Therefore the SEC and YRV rainfalls become out of phase.

The SEC wet phase in 1978–96 depends on an anomalous 850-hPa cyclone in the East China Sea. This anomalous cyclone, which transports moist air onshore from the east resulting in maximum moisture convergence in SEC, develops when the western Pacific subtropical ridge is weak and displaced equatorward. The flow is more baroclinic and the monsoon fronts are active in the southeast coastal area. In this case the SEC and YRV rainfalls are uncorrelated.

The July and August SEC wet phases show opposite characteristics. The wet July phase depends on anomalous 850-hPa cyclonic circulation in the northern South China Sea (and the East China Sea during 1951–77), which requires a retreat of the western edge of the western Pacific subtropical ridge. The anomalous South China Sea cyclone may be due to more frequent tropical cyclone activity. This is in contrast to the wet August phase, which is associated with anomalous anticyclones in the northern South China Sea and a greater westward extension of the subtropical ridge.

* Current affiliation: IPRC, University of Hawaii, Honolulu, Hawaii.

Corresponding author address: Dr. C.-P. Chang, Dept. of Meteorology, Naval Postgraduate School, Monterey, CA 93943.

Email: cpchang@nps.navy.mil

Save