Presentation by Marco Bajo (ISMAR, Italy), at the DANUBIUS Modelling Workshop, during Delft Software Days - Edition 2019. Friday, 8 November 2019, Delft.

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Modelling of the Danube Delta
and of the Razelm-Sinoe lagoon
Marco Bajo12*, Irina Dinu2, Georg Umgiesser1, Adrian Stanica2
1 Institute of Marine Sciences (ISMAR), Venice, Italy
2 National Institute for Marine Geology and Geoecology,
GEOECOMAR, Bucharest, Romania
* marco.bajo@ismar.cnr.it

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Summary
• Black Sea and Danube delta modelling;
• Validation;
• Results;
• Razelm-Sinoe modelling;
• Sensitivity simulation results;
• Conclusions.

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Model:
⚫ Shallow water equations;
⚫ 3D formulation with z-layers;
⚫ Baroclinic terms;
⚫ Vertical turbulence with GOTM.
SHYFEM: Shallow water equations

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Model domain: grid
Horizontal resolution:
- 83,938 elements
- Maximum size ~ 12km
- Minimum size < 50m
- Higher resolution near the Romanian coast
Vertical resolution:
The first layer is 2m thick, then the
layers gradually increase with depth.
Surface is well defined, with 8 layers
in 20m.

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Initial conditions: temperature and salinity
Temperature and salinity from
the ADCP data merging of the
MEDAR project. Data are in a
0.1 horizontal grid and 21
vertical levels.

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Initial conditions: temperature and salinity
Spin-up:
⚫ Simulation with T/S fields constant in time for some
weeks (January climatology) → steady baroclinic
simulation;
⚫ Simulation 2-year long. First year was considered
spin-up time, second year (2009) was used in the
results.

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Lateral boundary condition: Danube
For the Danube water discharge we used 2009 data from two sources
(Bajo et al., 2014). Dniepr river, as well as other rivers, are
climatological.
Danube branches: Kilia = 60%, Sulina = 20%, St. Gheorge = 20%

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Lateral boundary condition
⚫ River salinity was set to zero;
⚫ Measured Danube water temperature was used;
⚫ Other rivers (South Bug, Ingul, Dnestr, Rioni, Coruh,
Kizil, Sakarya, Yesil Irmak, Kodori, Bzyb) were
considered with climatological yearly discharges;
⚫ Bosphorus strait with monthly discharge and a 2-
layer flow triggered by different salinity (surface layer
20 PSU, bottom layer 37 PSU).

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Surface boundary conditions
ECMWF fields, 0.5 degrees, 6 hours:
• 10m wind
• Surface atmospheric pressure
NCEP/NCAR Reanalysis Project (NOAA/ESRL Physical
Sciences Division), 2 degrees, 6 hours:
• Solar radiation
• Cloudiness
• Humidity
• Rain
• Air temperature
HEAT MODULE

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VALIDATION: sea level

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VALIDATION: SST

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VALIDATION: Temperature profiles
1-2 June 2009

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VALIDATION: Salinity profiles
1-2 June 2009

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RESULTS: Salinity average maps
3-month average (Spring)

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RESULTS: Salinity average maps
3-month average (Autumn)

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Conclusions: Danube delta
• Set-up of a high resolution 3D baroclinic model for
the Danube delta;
• Validation in 4 stations. Correlation 0.9 for surface
temperature, 0.7 for sea level;
• Temperature and salinity profiles: too much mixing at
the surface;
• Wind is the primary factor determining the direction of
the plume;
• In winter and spring two anticyclonic eddies can form
with freshwater south of St. Gheorge and Kilia
branches;
• Further measurements are necessary to study the
Delta dynamics more in details.

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Razelm-Sinoe: study area
• The Razelm-Sinoe lagoon is a
brackish water system south of
the Danube St. Gheorge
branch;
• Some channels link the system
to the Danube branch.

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Razelm-Sinoe: freshwater input
• We have daily discharges of
the three channels (Dunavat,
Mustaca and Dranov) for
three years.
2003
2004
2006

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Razelm-Sinoe: grid
• The two sub-
basins have
small
communication
channels;
• Connection with
the sea is often
closed;
• 18,917
elements;
• Max depth = 3m

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Razelm-Sinoe: salinity results
2003 2004
• Simulations
with real wind,
temperature
and salinity;
• Temperature
and salinity are
transported;
• Simulations of
three years:
2003, 2004,
2006

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Razelm-Sinoe: salinity results
2006

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Razelm-Sinoe: water renewal time
WRT is high in general, but can be reduced by freshwater inputs
and the wind. Exchanges with the sea are limited.

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Conclusions: Razelm-Sinoe
• Some preliminary simulations have been run;
• More complex simulations are planned, with a full-
baroclinic set-up and real forcing;
• Results show limited dynamics, regulated mainly by
the wind;
• No tidal action and negligible water exchanges with the
sea;
• More data are needed.

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References:
Bajo, Marco, Ferrarin, Christian, Dinu, Irina, Umgiesser, Georg, Stanica,
Adrian. (2014). The water circulation near the Danube Delta and the
Romanian coast modelled with finite elements. M Bajo, C Ferrarin, I Dinu,
G Umgiesser, A Stanica. Continental Shelf Research 78, 62-74.
Dinu, Irina, Umgiesser, Georg, Bajo, Marco, De Pascalis, Francesca,
Stanica, Adrian, Pop, Cornel, Dimitriu, Radu, Nichersu, Iulian,
Constantinescu, Adrian. (2015). Modelling of the response of the Razelm-
Sinoe lagoon system to physical forcing. 5-18. 10.5281/zenodo.45064.