Abnormal upwelling and chlorophyll-a concentration off South Vietnam in summer 2007

Liu, X., J. Wang, X. Cheng, and Y. Du (2012), Abnormal upwelling and chlorophyll-a concentration off South Vietnam in summer 2007, J. Geophys. Res., 117, C07021, doi:10.1029/2012JC008052.


The present study investigates a strong upwelling and concurrent phytoplankton bloom off the South Vietnam coast in August 2007. Analysis of the alongshore wind, offshore Ekman transport, wind stress curl and other parameters indicates the southwesterly summer monsoon plays an important role in this peculiar case. The change of monsoonal wind involves variations of atmospheric circulation on multiple time scales. On the interannual time scale, a positive Indian Ocean Dipole (IOD) in 2007 accompanying with a La Niña event acts to enhance the southwesterly monsoon over the South China Sea (SCS). The enhanced southwesterly wind is regarded as a major factor in promoting the upwelling and the phytoplankton bloom off the South Vietnam coast. On the intraseasonal time scale, variations of the sea surface temperature (SST) and sea surface wind at 30-60 day periods reveal that the SST cooling develops with the evolution of the southwesterly wind anomalies with nearly one week delay, implying the great significance of the Madden-Julian Oscillation (MJO). Moreover, a tropical storm formed in the western SCS in early August reinforces the westerly wind and SST cooling. Among multiple factors on different time scales, the MJO event is considered as the major cause, since it induces the maximum velocity (4 m/s) of the southwesterly wind anomalies. As a result, the high Chlorophyll-a concentration (>0.56 mg/m3) and low SST center (<27 {degree sign}C) develops in the region off the South Vietnam coast and advects to the central SCS, riding on the northern rim of the southern anticyclonic gyre.


  • Chlorophyll-a concentration
  • El Niño
  • Indian Ocean dipole
  • Madden-Julian Oscillation
  • South Vietnam coast
  • upwelling

Underwater optical environment in the Upper Gulf of Thailand

Matsumura, Satsuki,Siripong, Absornsuda,Lirdwitayaprasit, Thaitherworn

Coastal marine science. Vol.30No.1, 2006.4, pp. 36-43


Because the composition of coastal water is full of variety by each region, relationship between chlorophyll-a (chl.a) concentration as a indicator of primary productivity derived by satellite ocean color data and in situ data of chl.a may not be same always. Those relations or algorithms should be verified at each coastal water for managing coastal environment. Coastal ocean color algorithms should be built up at each coastal water or at least should be verified by wide range field data for practical application at each region. Intensive research cruises were conducted at the Upper Gulf of Thailand. Optical survey using PRR (Profiling Reflectance Radiometer) showed the character of the Upper Gulf water. Under water optical algorithms for that water were suggested by these survey data. Optical depths in the Gulf of Thailand were also measured to know the compensation depth for primary production. Although the transparency measured by Secchi disk is not so large and surface water looks very turbid, the light energies are reaching to near bottom at almost all stations of the upper Gulf. It suggests that the turbidity of this water were mainly composed of scattering material like as clay mineral rather than absorbing material like as phytoplankton pigment or CDOM.


  • coastal water algorithm
  • PAR
  • compensation depth
  • chlorophyll-a
  • CDOM
  • SS
  • satellite
  • remote sensing

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Spatial and seasonal variability of Chlorophyll-a and associated oceanographic events in Sabah water

Abbas, Alaa A.,Mansor, Shattri B. ; Pradhan, Biswajeet ; Tan, C.K.,2012. Spatial and seasonal variability of Chlorophyll-a and associated oceanographic events in Sabah water.The Second International Workshop on Earth Observation and Remote Sensing Applications (EORSA 2012), pp 215-219. DOI 10.1109/EORSA.2012.6261168.


This study investigated the spatial and temporal distributions of Chlorophyll-a (Chl-a) in Sabah coastal water using satellite data, and identified the associated oceanographic events which caused large scale water enrichment in the surface layer. Results showed that surface Chl-a experienced seasonality in Sabah waters. At the northwest coast, very obvious increase in the Chl-a was observed from January to March, attributed to wind-driven coastal upwelling during the northeast monsoon (NEM). The southeast coast depicted high Chl-a at Labuan offshore water, related to the reversing direction of Baram River plume towards Sabah during NEM. Labuan bay water had higher Chl-a during the southwest monsoon (SWM) due to the effect of discharged materials from the Padas River during the rainy season at Labuan. On the other side, a slight increase in surface Chl-a was illustrated along the entire northeast coast during NEM, with higher concentrations at the southern part compared to the northern region. The high Chl-a at the southern part (southern Sandakan) was owing to alongshore water transport from the northern region driven by NEM winds and effect of discharged materials from the Kinabatangan River during the rainy season at Sandakan. Water characteristic at the southeast coast was highly influenced by surface water transport from the Sulu and Sulawesi seas and prevailed surface currents. Both inshore and offshore waters off Semporna had peak Chl-a in December, related to Sulu Sea water transport towards Semporna and occurrence of cyclonic eddy at the offshore water during early NEM. Tawau water showed very high Chl-a throughout the year due to the effect of coastal discharge. The discharged material near Tawau was transported to a wider area offshore during SWM. That in turn caused another peak Chl-a at Semporna inshore water in August during SWM.


  • Asian monsoon
  • Sabah water
  • chlorophyll-a
  • seasonal variation
  • upwelling