Summer upwelling in the South China Sea and its role in regional climate variations

Seasonal and interannual variations of summer upwelling off the South Vietnam coast and the offshore spread of cold water are investigated using a suite of new satellite measurements. In summer, as the southwesterly winds impinge on Annam Cordillera (a north-south running mountain range on the east coast of Indochina) a strong wind jet occurs at its southern tip offshore east of Saigon, resulting in strong wind curls that are important for ocean upwelling off the coast. In July and August an anticyclonic ocean eddy develops to the southeast, advecting the cold coastal water offshore into the open South China Sea (SCS). The center of this cold filament is located consistently north of the wind speed maximum, indicating that open-ocean upwelling helps to cool the ocean surface. Corroborating evidence for the cold filament is found in ocean color observations that reveal a collocated tongue of high chlorophyll concentration. The development of this cold filament disrupts the summer warming of the SCS and causes a pronounced semiannual cycle in SST. Moreover, the cold filament is an important player in interannual variability in the summer SCS. In 1998, the cold filament and mid-summer cooling never took place, giving rise to a strong basin-wide surface warming. Interannual SST variance has a local maximum over the climatological cold filament, and is much greater than the variance over the adjacent Indian and western Pacific Oceans. A cold filament index is constructed, which displays significant lagged correlation with SST in the eastern equatorial Pacific and Indian Oceans, indicative of a teleconnection from El Nino.

[1]  James T. Potemra,et al.  Coupled dynamics over the Indian Ocean: spring initiation of the Zonal Mode , 2003 .

[2]  Xiaosu Xie,et al.  Atmospheric manifestation of tropical instability wave observed by QuikSCAT and tropical rain measuring mission , 2000 .

[3]  Hou Yi-jun,et al.  Sea surface height and transport stream function of the South China Sea from a variable-grid global ocean circulation model , 2003 .

[4]  T. Qu.  Role of ocean dynamics in determining the mean seasonal cycle of the South China Sea surface temperature , 2001 .

[5]  Edward M. Armstrong,et al.  A new global satellite‐based sea surface temperature climatology , 2001 .

[6]  Yan Du,et al.  The 1997–1998 warm event in the South China Sea , 2002 .

[7]  R. Lu.  Convective activities in the tropical western Pacific and their impact on the northern hemisphere summer circulation , 1987 .

[8]  谢强,et al.  Comparison among four kinds of data of sea surface wind stress in the South China Sea , 2002 .

[9]  T. Pohlmann.  A Three Dimensional Circulation Model of the South China Sea , 1987 .

[10]  Phillip A. Arkin,et al.  Analyses of Global Monthly Precipitation Using Gauge Observations, Satellite Estimates, and Numerical Model Predictions , 1996 .

[11]  Xie Qiang,et al.  Comparison among four kinds of data of sea surface wind stress in the South China Sea , 2002 .

[12]  S. Xie,et al.  Structure and Mechanisms of South Indian Ocean Climate Variability , 2002 .

[13]  G. Duclos.  New York 1987 , 2000 .

[14]  Richard H. Johnson,et al.  A Report of the Field Operations and Early Results of the South China Sea Monsoon Experiment (SCSMEX) , 1999 .

[15]  W. Timothy Liu,et al.  Spacebased observations of the seasonal changes of south Asian monsoons and oceanic responses , 1999 .

[16]  Masaki Ishiwatari,et al.  Coupled ocean‐atmospheric waves on the equatorial front , 1998 .

[17]  S. Chao,et al.  Surface circulation in the South China Sea , 1994 .

[18]  Bin Wang,et al.  Pacific–East Asian Teleconnection: How Does ENSO Affect East Asian Climate? , 2000 .

[19]  Q. Zheng,et al.  Dynamically Active Areas in the South China Sea Detected from TOPEX/POSEIDON Satellite Altimeter Data , 2000 .

[20]  Akimasa Sumi,et al.  Far‐reaching effects of the Hawaiian Islands in the CCSR/NIES/FRCGC high‐resolution climate model , 2004 .

[21]  Gilles Reverdin,et al.  Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and -2 , 2000 .

[22]  C. W. Li,et al.  Current Characteristics Of The South China Sea , 1994 .

[23]  F. Schott,et al.  The monsoon circulation of the Indian Ocean , 2001 .

[24]  Yuqing Wang,et al.  Regional Model Simulations of Marine Boundary Layer Clouds over the Southeast Pacific off South America. Part II: Sensitivity Experiments* , 2004 .

[25]  Q. Xie,et al.  Seasonal structures of upper layer circulation in the southern South China Sea from in situ observations , 2002 .

[26]  Michael H. Freilich,et al.  Observations of coupling between surface wind stress and sea surface temperature in the Eastern Tropical Pacific , 2001 .

[27]  Dongxiao Wang,et al.  A general circulation model study of the dynamics of the upper ocean circulation of the South China Sea , 2002 .

[28]  Thomas M. Smith,et al.  Improved Global Sea Surface Temperature Analyses Using Optimum Interpolation , 1994 .

[29]  W. Kessler,et al.  Mean Three-Dimensional Circulation in the Northeast Tropical Pacific* , 2002 .

[30]  Cheinway Hwang,et al.  Circulations and eddies over the South China Sea derived from TOPEX/Poseidon altimetry , 2000 .

[31]  K. Lau,et al.  Hydrologic processes associated with the first transition of the Asian summer monsoon : A pilot satellite study , 1998 .

[32]  John C. Ries,et al.  Chapter 1 Satellite Altimetry , 2001 .

[33]  Masami Nonaka,et al.  Covariations of Sea Surface Temperature and Wind over the Kuroshio and Its Extension: Evidence for Ocean-to-Atmosphere Feedback(. , 2003 .

[34]  Shang-Ping Xie,et al.  Satellite Observations of Cool Ocean–Atmosphere Interaction , 2004 .

[35]  P. Chu,et al.  An airborne expendable bathythermograph survey of the South China Sea, May 1995 , 1998 .

[36]  W. Liu,et al.  Local and remote atmospheric response to tropical instability waves: A global view from space , 2001 .

[37]  Chung-Ru Ho,et al.  Satellite Observation of Upwelling along the Western Coast of the South China Sea , 2000 .

[38]  W. Liu,et al.  Far-Reaching Effects of the Hawaiian Islands on the Pacific Ocean-Atmosphere System , 2001, Science.

[39]  K. Wyrtki.  Physical oceanography of the Southeast Asian waters , 1961 .

[40]  Smith,et al.  Satellite measurements of sea surface temperature through clouds , 2000, Science.

[41]  A. Kitoh,et al.  Sea Surface Temperature in the South China Sea , 1997 .

[42]  T. Qu,et al.  Upper-Layer Circulation in the South China Sea* , 2000 .

[43]  Chung-Ru Ho,et al.  Seasonal variability of sea surface height in the South China Sea observed with TOPEX/Poseidon altimeter data , 2000 .

[44]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.