HILO joint Laboratory was set up in 2014 based on a strong partnership with Vietnamese (IMER, IO, STI and VNU-HUS) and French (LEGOS, LOG, LA) research teams.
The HILO laboratory of oceanography aims at understanding and forecasting the functioning and variability of the coupled hydrodynamical-biogeochemical system in the regional and coastal marine areas. Due the strong coupling between the dynamical and biological processes, as well as the multiple spatial and temporal scales involved, oceanography is fundamentally a multidisciplinary science. Its study requires the involvement of different specialties and the combination of a large range of tools. To reach its objectives, HILO therefore gathers scientists of different disciplines (physics, optics, biogeochemistry, geology...) who use state of the arts tools : satellite and in situ observations, numerical modeling and assimilation techniques. The large field of research covered in the frame of this laboratory allows a large community of institutes, researchers, and students (PhD, Master students) to be involved. It also allows to answer to large panel of research funding from national and international calls in collaboration with the different Vietnamese institutes and French universities and laboratories involved in this project. The presence in Vietnam of the two PI of the project through the IRD program is a great advantage for the efficient implementation of HILO.
• Identify and understand the physical and biogeochemical processes involved in the functioning of the oceanic system,
• Understand its variability at different scales (daily to long term evolution) and identify the factors that trigger those scales of variability (atmospheric, oceanic, hydrological, anthropogenic...),
• Forecast the evolution of the oceanic system, from the short-term scales (operational forecast) to the long-term evolution (impact of climate change).
High-resolution coupled physical-biogeochemical modeling, multi-sensors satellite observations, in-stu measurements and assimilation are used complementarily to answer these questions. Several PhD (7 presently) and Master students are trained within HILO. This gives them the opportunity to work in the frame of an international and highly interdisciplinary laboratory, and to learn different technical and scientific approaches relevant to environmental studies.
3. Current research activities
- High Performance Computing (HPC) facilities for modeling and satellite data treatment: a 100-cores IBM server cluster was installed in 2016 at USTH for the HILO and REMOSAT groups (French Embassy funding).
- The WEO 90 m2 platform for water samples analysis is located at USTH and is furnished with a large range of high technology instruments. It used for research and training.
- In-situ equipment for field campaigns in marine and river environment available at USTH (balance, turbidimeter, ADCP, Niskin bottle to sample seawater, etc).
Our research activities are organized around differents and complementaries tasks:
- Impact of ocean dynamics on marine ecosystems
Coupled models are used to study the hydrodynamical processes in regional and coastal regions of Vietnam, and to assess their impact of the marine pelagic planktonic ecosystems, which are the first level of the trophic chain. We use SYMPHONIE, Delft3D and ROMS ocean models. In particular the SYMPHONIE model is developed by the SIROCCO group that provides a strong support to HILO in terms of training, students’ supervision, numerical configurations developement and improvement and results analysis. This model is particularly adapted to our activities: it allows to implement variable size grid therefore to zoom over some area of interest, and it is coupled to the model ECO3M-S that represents the biogeochemical interactions inside the pelagic planktonic ecosystem.
Mean summer sea surface elevation and associated surface circulation in the altimetry data (left) and a ROMS 1/12 simulation (right)
- Fate and transport of suspended sediment
The Gulf of Tonkin waters are submitted to huge suspended matter continental input coming from the Red River. We focus on coastal suspended sediment transport as well as factors relative to this process in the Red River estuarine and coastal zones. We perform intensive in-situ measurements campaign as well as numerical simulations : the SYMPHONIE model is coupled to a state of the art sediment transport model developed by IFREMER (France), and we also use the Delft3D finite element model.
Deflt3D model results: suspended sediment distribution in June (Left) and September (right) 2014
- Algorithm development for satellite observations
We develop new algorithms especially designed for coastal regions to assess the surface chlorophyll content from Ocean Color satellite data in those areas, and test them over in situ datasets. In particular, for all visible imagery, clouds are impacting the quantity and quality of observations. Assumptions made regarding marine reflectance for open-ocean waters are not valid for coastal turbid waters due to suspended matter and non-maritime aerosols. A special attention must be given to cloud free/shadow/masking pixels dealing when working with high spatial resolution data. We therefore develop new tools for cloud masking in satellite images for coastal regions. Combination of satellite images and results from numerical model allows to understand the observed spatio-temporal variability of chlorophyll concentration.
Comparison of SPM estimated by Landsat -8 images in rainy season (left) and dry season (right) in Haiphong coastal areas and Bachdang estuary.
- - In-situ observations collection, treatment and analysis
Numerical modeling tools and satellite observations must be used in combination with in-situ data.
Several oceanographic surveys dedicated to the observation of the estuarine and coastal regions in the Red river and Mekong river estuaries and plumes took place between 2012 and 2016, in particular in the framework of the VIETNAMINS (USTH), VITEL (CNES/TOSCA), GlobCoast (ANR) projects and MERIS 4th Reprocessing (ESA) projectsm in strong collaboration with colleagues from STI and IMER.
Glider surveys should be performed in in 2017-18 in the Central Vietnam Upwelling region (~11°N), in cooperation with IO, IRD and CNRS. The objectives are to build a fine scale description of the water masses hydrological and biogeochemical characterstics and of their seasonal variability, and to study the role of submesoscale dynamics in this region.
Measurements stations for the Cam River estuary survey, September 2015
4. Training and education
HILO contributes to the training of Vietnamese students and researchers in the modeling and observation of the coastal river-estuary-ocean continuum and to the connection between training and research activities at USTH. First, most of the researchers of HILO are teachers in WEO and Space USTH Masters. Second, HILO provides a cooperative framework for the supervision of Bachelor, Master and PhD students. This gives them the opportunity to work in an interdisciplinary and international environment, learning different technical and scientific approaches relevant to environmental studies.
Training schools on specific aspects of the modeling and observation of the coupled ocean-atmosphere system, for which a strong demand exists in Vietnam, are organized on a yearly basis. Seminars are also regularly organized during research or training visits of exterior scientists.
Training school in oceanography modeling provided the SIROCCO team for young researchers in March 2016.
5. Selected publications
Loisel, H., V. Vantrepotte, S. Ouillon, Dat Dinh Ngoc, M. Herrmann, Viet Tran, X. Mériaux, D. Dessailly, C. Jamet, T. Duhaut, Huan Huu Nguyen, Thao Van Nguyen. Assessment and analysis of the Chlorophyll-a concentration variability over the Vietnamese coastal waters from the MERIS ocean color sensor (2002-2012). Rem. Sens. Env. In press.
Han B., Loisel H., Vantrepotte V., Mériaux X., Bryère P., Ouillon S., Dessailly D., Xing Q., Zhu J., 2016. Development of a semi-analytical algorithm for the retrieval of Suspended Particulate Matter from remote sensing over clear to very turbid waters, Remote Sensing, 8, 211; doi:10.3390/rs8030211
Vinh V.D., Ouillon S., Thao N.V., Tien N.N., 2016. Numerical Simulations of Suspended Sediment Dynamics Due to Seasonal Forcings in the Mekong Coastal Area, Water, 8, 255, doi:10.3390/w8060255
Vantrepotte V., Danhiez F.P., Loisel H., Ouillon S., Mériaux X., Cauvin A., Dessailly D., 2015. CDOM-DOC relationship in contrasted coastal waters : implication for DOC retrieval from ocean color remote sensing observation, Optics Express, 23 (1), 33-54, doi:10.1364/OE.23.000033
Loisel H., Mangin A., Vantrepotte V., Dessailly D., Dinh Ngoc Dat, Garnesson P., Ouillon S., Lefebvre J.P., Mériaux X., Phan Minh Thu, 2014. Analysis of the suspended particulate matter concentration variability of the coastal waters under the Mekong’s influence: a remote sensing approach, Remote Sensing of Environment, 150, 218-230. DOI: 10.1016/j.rse.2014.05.006
Nguyen, N.M., P. Marchesiello, F. Lyard, S. Ouillon, G. Cambon, D. Allain, U.V. Dinh, 2014: Tidal characteristics of the Gulf of Tonkin. Continental Shelf Research, 91, 37-56, doi:10.1016/j.csr.2014.08.003.
Vinh V.D., Ouillon S., Tran Duc Tanh, La Van Chu, 2014. Impact of the Hoa Binh dam (Vietnam) on water and sediment budgets in the Red River basin and delta, Hydrology and Earth System Sciences, 18 (10), 3987-4005, doi:10.5194/hess-18-3987-2014
Institute of Marine Environment and Resources (IMER), VAST, Vietnam
Institute of Oceanography (IO, VAST), Vietnam
Space Technology Institute
(STI), VAST, Vietnam
Institut de Recherche pour le Développement (IRD), France
7. HILO Staffs
Université Fédérale Toulouse Midi-Pyrénées (UFTMIP), France
*) Vietnamese Institutions researchers
Nguyen Nguyet Minh, USTH
Trinh Bich Ngoc, USTH
Dinh Ngoc Dat, STI, VAST
Vu Duy Vinh, IMER, VAST
To Duy Thai, IO, VAST
Nguyen Minh Huan, VNU-HUS
*) French Institutions Researchers
Marine Herrman, LEGOS/IRD
Sylvain Ouillon, LEGOS/IRD
Fernando Nino, LEGOS/IRD
Florent Lyard, LEGOS/CNRS
Sylvain Biancamaria, LEGOS/CNRS
Rosemarry Morrow, LEGOS/ UFTMIP
Thomas Duhaut, LA/CNRS
Patrick Marsaleix, LA/CNRS
Caroline Ulses, LA/ UFTMIP
Hubert Loisel, LOG/ULCO
Cédric Jamet, LOG/ULCO
Alexei Sentchev, LOG/ULCO
*) PhD students
Vu Duy Vinh, IMER
Dinh Ngoc Dat, STI
Trinh Bich Ngoc, PhD student, USTH
Tran Trung Kien, LOG, ULCO fellowship
Nguyen Dac Da, LEGOS / VNU-HUS, ARTS IRD fellowship
Violaine Piton, LEGOS, MESR fellowship