scholarly journals Monthly anomalies of sea surface chlorophyll-a concentration in the Khanh Hoa waters of Vietnam related to ENSO phenomenon

2021 ◽  
Vol 21 (3) ◽  
pp. 233-245
Author(s):  
Van Tac Vu
Keyword(s):  
Chlorophyll A ◽  
Marine Ecosystem ◽  
La Niña ◽  
Sea Surface ◽  
Concentration Data ◽  
Chlorophyll A Concentration ◽  
La Nina ◽  
Average Variation ◽  
La Nina Event ◽  
The Impact

Based on the monthly averaged sea surface chlorophyll-a concentration data continuously for more than 17 years (Jul. 2002–Dec. 2019), the analyzed results show that the averaged chlorophyll-a concentration in Khanh Hoa waters was 0.58 mg/m3, and the monthly average variation was ± 0.14 mg/m3 (that is equivalent to about ± 24%). Under the impact of ENSO phenomena, in the years when the double La Niña events occurred (two consecutive years in the La Nina event occurs), the chlorophyll-a anomaly index fluctuated from -0.99 mg/m3 to 1.62 mg/m3. These are very strong fluctuation levels, corresponding to the decrease or increase in chlorophyll-a concentration from 86% to 279%. In the El Niño years, the fluctuations of chlorophyll-a concentration were little affected unless the two previous years in which the double La Niña event occurred. These fluctuations have significantly impact nutritional resources and water quality because chlorophyll-a concentration is one of the key indices in studying the health status of any natural marine ecosystem. In addition, chlorophyll-a concentration in Khanh Hoa waters often varies between seasons. The averaged chlorophyll-a concentration reaches its maximum value in the winter, then decreases gradually in the spring and usually reaches the minimum value in the summer, then rises gradually again in the autumn.

scholarly journals BẤT THƯỜNG CỦA HÀM LƯỢNG CHLOROPHYLL TẦNG MẶT TẠI VÙNG BIỂN VEN BỜ NAM TRUNG BỘ VIỆT NAM LIÊN QUAN ĐẾN HIỆN TƯỢNG ENSO

2018 ◽  
Vol 18 (1) ◽  
pp. 70-78
Author(s):  
Vu Van Tac ◽  
Doan Nhu Hai
Keyword(s):  
Chlorophyll Concentration ◽  
La Niña ◽  
Environment Change ◽  
Concentration Data ◽  
Marine Area ◽  
South Central ◽  
La Nina ◽  
Coastal Marine ◽  
The Impact ◽  
Anomaly Index

The studies on the impact of the ENSO phenomenon on climate and environment change have shown that the Bien Dong (Southeast Asia Sea) is strongly influenced by this phenomenon. This paper focuses on analyzing sea surface chlorophyll concentration data in the coastal marine area of Vietnam South Centre from MODIS satellite images of National Aeronautics and Space Administration (US NASA). The analysis results have shown that there is no obvious difference of the chlorophyll anomaly index between El Niño and neutral years. However, in La Niña years the chlorophyll anomaly index is greatly varied and generally inversely proportional to the ONI index, which means chlorophyll anomaly index rises while ONI index falls. The impact has made chlorophyll in summer and autumn of La Niña years higher by 0.22 - 0.38 mg/m3 in comparison with other years. In terms of trends, chlorophyll concentration in the Vietnam South Central Coast fluctuates according to the seasons and months. The average chlorophyll concentration usually reaches its maximum value in the Autumn (Sep. - Nov.), then decreases in the Winter (Dec. - Feb.) and usually reaches the minimum value in the Spring (Mar. - May), then rises gradually in the Summer (June - Aug.). The above results have contributed to improving understanding of the impact of the climatic vagaries on the coastal marine area of Vietnam South Centre, supported scientists and managers in proposing measures to prevent, avoid efficiently, limit and mitigate the damage caused by ENSO, and in having reasonable alternatives in the protection of biodiversity as well as environment in the coastal marine area of Vietnam South Centre. It could be considered as a “small piece” of the overall picture of the impacts of the ENSO phenomenon on global climate change.

Annual record of particle fluxes, geochemistry and diatoms in Effingham Inlet, British Columbia, Canada, and the impact of the 1999 La Niña event

2013 ◽  
Vol 337 ◽  
pp. 20-34 ◽  
Author(s):  
Alice S. Chang ◽  
Miriam A. Bertram ◽  
Tara Ivanochko ◽  
Stephen E. Calvert ◽  
Audrey Dallimore ◽  
...  
Keyword(s):  
British Columbia ◽  
La Niña ◽  
La Nina ◽  
Particle Fluxes ◽  
La Nina Event ◽  
The Impact ◽  
Effingham Inlet

scholarly journals ANALYSIS OF WATER PRODUCTIVITY IN THE BANDA SEA BASED ON REMOTE SENSING SATELLITE DATA

2020 ◽  
Vol 17 (1) ◽  
pp. 25
Author(s):  
Sartono Marpaung ◽  
Risky Faristyawan ◽  
Anang Dwi Purwanto ◽  
Wikanti Asriningrum ◽  
Argo Galih Suhada ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
El Niño ◽  
El Nino ◽  
Dry Season ◽  
La Niña ◽  
Wet Season ◽  
Conservation Areas ◽  
Conservation Area ◽  
Chlorophyll A Concentration ◽  
La Nina

Abstract. This study examines the density of potential fishing zone (PFZ) points and chlorophyll-a concentration in the Banda Sea. The data used are those on chlorophyll-a from the Aqua MODIS satellite, PFZ points from ZAP and the monthly southern oscillation index. The methods used are single image edge detection, polygon center of mass, density function and a Hovmoller diagram. The result of the analysis show that productivity of chlorophyll-a in the Banda Sea is influenced by seasonal factors (dry season and wet season) and ENSO phenomena (El Niño and La Niña). High productivity of chlorophyll-a  occurs during in the dry season with the peak in August, while low productivity occurs in the wet season and the transition period, with the lowest levels in April and December. The variability in chlorophyll-a production is influenced by the global El Niño and La Niña phenomena; production increases during El Niño and decreases during La Niña. Tuna conservation areas have as lower productivity of chlorophyll-a and PFZ point density compared to the northern and southern parts of the Banda Sea. High density PFZ point regions are associated with regions that have higher productivity of chlorophyll-a, namely the southern part of the Banda Sea, while low density PFZ point areas  are associated with regions that have a low productivity of chlorophyll-a, namely tuna conservation areas. The effect of the El Niño phenomenon in increasing chlorophyll-a concentration is stronger in the southern part of study area than in the tuna conservation area. On the other hand, the effect of La Niña phenomenon in decreasing chlorophyll-a concentration is stronger in the tuna conservation area than in the southern and northern parts of the study area. 

Modelling the impact of a La Niña event on a South West Pacific Lagoon

2012 ◽  
Vol 64 (8) ◽  
pp. 1596-1613 ◽  
Author(s):  
R. Fuchs ◽  
C. Dupouy ◽  
P. Douillet ◽  
M. Caillaud ◽  
A. Mangin ◽  
...  
Keyword(s):  
La Niña ◽  
West Pacific ◽  
La Nina ◽  
South West ◽  
La Nina Event ◽  
The Impact

The Impact of ENSO on Wave Breaking and Southern Annular Mode Events

2010 ◽  
Vol 67 (9) ◽  
pp. 2854-2870 ◽  
Author(s):  
Tingting Gong ◽  
Steven B. Feldstein ◽  
Dehai Luo
Keyword(s):  
El Niño ◽  
Wave Breaking ◽  
El Nino ◽  
Southern Annular Mode ◽  
La Niña ◽  
Background Flow ◽  
Austral Spring ◽  
Annular Mode ◽  
La Nina ◽  
The Impact

Abstract This study examines the relationship between intraseasonal southern annular mode (SAM) events and the El Niño–Southern Oscillation (ENSO) using daily 40-yr ECMWF Re-Analysis (ERA-40) data. The data coverage spans the years 1979–2002, for the austral spring and summer seasons. The focus of this study is on the question of why positive SAM events dominate during La Niña and negative SAM events during El Niño. A composite analysis is performed on the zonal-mean zonal wind, Eliassen–Palm fluxes, and two diagnostic variables: the meridional potential vorticity gradient, a zonal-mean quantity that is used to estimate the likelihood of wave breaking, and the wave breaking index (WBI), which is used to evaluate the strength of the wave breaking. The results of this investigation suggest that the background zonal-mean flow associated with La Niña (El Niño) is preconditioned for strong (weak) anticyclonic wave breaking on the equatorward side of the eddy-driven jet, the type of wave breaking that is found to drive positive (negative) SAM events. A probability density function analysis of the WBI, for both La Niña and El Niño, indicates that strong anticyclonic wave breaking takes place much more frequently during La Niña and weak anticyclonic wave breaking during El Niño. It is suggested that these wave breaking characteristics, and their dependency on the background flow, can explain the strong preference for SAM events of one phase during ENSO. The analysis also shows that austral spring SAM events that coincide with ENSO are preceded by strong stratospheric SAM anomalies and then are followed by a prolonged period of wave breaking that lasts for approximately 30 days. These findings suggest that the ENSO background flow also plays a role in the excitation of stratospheric SAM anomalies and that the presence of these stratospheric SAM anomalies in turn excites and then maintains the tropospheric SAM anomalies via a positive eddy feedback.

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