Marine Meteorology

Diagnostic analysis of abnormal meridional circulation during strong/weak South China Sea Summer Monsoon

  • WU Dong-mei ,
  • LU Wei-song ,
  • WU Nai-geng ,
  • QI Jin-dian ,
  • YANG Lei ,
  • LIU Qin-yan ,
  • WANG Dong-xiao
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  • 1. Department of Atmospheric Science, Nanjing University of Information Science & Technology, Nanjing 210044, China; 2. State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China; 3. Guangzhou Central Meteorological Observatory, Guangzhou 510080, China; 4. Department of Atmospheric Science, Sun Yat-sen University, Guangzhou 510275, China;

Received date: 2012-06-27

  Revised date: 2012-09-21

  Online published: 2013-11-21

Abstract

Based on the National Centers for Environmental Prediction/the National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset, the meridional circulation of the South China Sea Summer Monsoon (SCSSM) in June-August from 1979 to 2010 is diagnosed using the linear diagnostic equation. The major processes that affect the meridional circulation of the SCSSM are discussed quantitatively. The anomalous meridional circulation indicates that the low-level (900-hPa) southerly over the SCS (10°-15°N) is stronger in strong SCSSM years than in normal years, and that in weak SCSSM years there exists stronger northerly in the SCS. The quantitative analysis shows that the contributions to the anomalous meridional component of the meridional circulation in the lower level over the SCS in anomalous strong SCSSM years are mainly from the processes related to latent heating (68%), boundary effect (or the effect of cross-equatorial flow) (14%), and air-sea latent-heat flux (12%). In weak SCSSM years, the contributions are mainly from the processes related to latent heat (46%), boundary effect (38%), and vertical transport of heat (13%). The general circulation associated with the major processes shows that the western Pacific Subtropical High (WPSH) related to latent heating and the Australia High (AH) associated with boundary effect have the opposite characteristics in strong/weak SCSSM years. Latent-heat flux also contributes to monsoon intensity. The distribution of latent-heat flux over the SCS is opposite in strong/weak SCSSM years. In the strong (weak) SCSSM years, the latent-heat flux anomalies is positive (negative) over the southern SCS and negative (positive) over the northern SCS.

Cite this article

WU Dong-mei , LU Wei-song , WU Nai-geng , QI Jin-dian , YANG Lei , LIU Qin-yan , WANG Dong-xiao . Diagnostic analysis of abnormal meridional circulation during strong/weak South China Sea Summer Monsoon[J]. Journal of Tropical Oceanography, 2013 , 32(5) : 48 -58 . DOI: 10.11978/j.issn.1009-5470.2013.05.007

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