www.tetratech.com

Weather Forecasting Services during

Marine Operations in the Angra dos Reis

Bay (RJ)

Application of Delft3D in an Operational Forecasting System

Delft3D Users Meeting 2014

INTRODUCTION

• In support for marine operations in Angra dos Reis Bay, Tetra Tech performed forecasting services of meteoceanographic conditions;

• Forecasts were obtained through a refined operational modeling system, coupling atmospheric and oceanic components;

• Local measurements of atmospheric, hydrodynamic and wave parameters were used to validate the numerical modeling products prior to the start of operations;

• During the marine operations period forecasting bulletins were provided with updating intervals of 12 hours.

STUDY LOCATION

• The Ilha Grande Bay is located in the Southern coast of

the state of Rio de Janeiro;

• This region has great importance ecologically, for

tourism and for the fishing industry, holding biological

reserves and environmentally protected areas;

• On the coast, besides the Central Nuclear Almirante

Álvaro Alberto – CNAAA (Nuclear Central Almirante

Álvaro Alberto), there are shipyard industries.

STUDY LOCATION

CIRCULATION PATTERNS

• According to Signorini (1980)

The circulation of the partially mixed estuarine system,

formed by the Ilha Grande Bay (IGB) and Sepetiba Bay

(SEPB), results from effects of tides, winds and density

gradients.

It can be observed the presence of a clockwise

(west-east) flux around Ilha Grande.

• The measured currents show a

clockwise (54,6% to E) and a

counter-clockwise flux

(41,2% to W).

OPERATIONAL PROCEDURE

• Bulletin updates were sent twice a day with forecasts for the following 72 hours of the environmental conditions predicted by the modeling system

• An alert system was implemented in the bulletins, indicating when the forecasted environmental conditions were according to established thresholds for the execution of transport and lifting procedures. The threshold values were given by the contractor for each procedure as:

Conditions for transport:

• Wind speed ≤ 14 knots

• Current speed ≤ 0.3 m/s

• Wave peak period (Tp) ≤ 10 s

• Significant wave height (Hs) ≤ 0.3 m

Conditions for lifting:

• Wind speed ≤ 10 knots

• Wave peak period (Tp) ≤ 7 s

• Significant wave height (Hs) ≤ 0.3 m

BULLETIN

EXAMPLE (1)

BULLETIN

EXAMPLE (2)

NUMERICAL MODELS

• The operational procedure to generate the metocean

forecasts in the Angra dos Reis Bay region was

composed with three kinds of numerical models:

Atmospheric model (WRF)

Two wave models (WW3 and SWAN)

Hydrodynamic model (Delft3D)

ATMOSPHERIC MODEL

• WRF (Weather Reserch and Forecasting)

NMM core (Nonhydrostatic Mesoscale Model), developed by

north American centers NOAA and NCEP.

Forced with global model data from the GFS (Global

Forecasting System), with spatial resolution of 0.5° and 3-

hour intervals. The GFS was developed and is maintained

by NCEP, with online available outputs in the spatial and

temporal resolution mentioned.

The WRF-NMM model was setup with two nested grids. The

coarser domain covered the Southeast region of Brazil, and

the second grid was refined over the coastal area.

WAVE MODEL

• Two third generation models were used:

WAVEWATCH III (WW3) and SWAN (Simulating

WAves Nearshore)

• Output results from WW3 were used as boundary

conditions for SWAN’s local grid, in a chain from

smaller to higher resolution grids.

• The high resolution atmospheric pressure and wind

fields from WRF outputs were also used for forcing

the high resolution SWAN grids.

HYDRODYNAMIC MODEL

• Delft3D-FLOW Hydrodynamic Model was

implemented in Angra dos Reis - Ilha Grande Bay;

• Delft3D-FLOW ran in a Domain Decomposition

scheme:

The outside grid (lower resolution grid) had 126 x 68 grid

cells and the high resolution grid had 104 x 86 grid cells

Horizontal resolution ranging from 1 kilometer to 300 meters

On the vertical axis 10 sigma layers have been used

High resolution bathymetric data was imposed in the

operations region

Hydrodynamic Forcing

• Meteorological forcing: outputs from the

atmospheric model WRF;

• 40 Riemann Boundaries (south, east and west)

* 10 sigma layers

HYCOM + TPXO composition

Riemann Invariants enable Delft3D to capture the

continental shelf dynamics and incorporate low frequency

signs

Riemann Invariants

25 Riemann Boundaries

8 Riemann Boundaries

7 Riemann

Boundaries

HYCOM (daily water level and currents) + TPXO

10 sigma layers

OPERATIONAL PROCEDURE FOR

DELFT3D

• WRF (wind and pressure) and HYCOM (currents and elevation) files are obtained from the FTP directory;

• The forcing (.bct and meteo) files for Delft3D are generated;

• The .mdf scenario is created;

• The restart files are copied from the last run (from 12 hours later);

• New scenario runs;

• The output files are generated by Quickplot;

• The output files are copied to the FTP.

A matlab script runs all the specified above twice a day.

MODEL EVALUATION

• The model was calibrated and validated through the

comparison of its results against measured data and

tidal prediction

• Tides (tidal prediction Angra dos Reis station)

RMAE 20

Index of Agreement 0,99

MODEL EVALUATION

• Currents (ADCP)

At this point there is a clockwise current with some

inversions to counter clockwise

The model represents this pattern coherently

Riemann Tide

Index of agreement U comp. = 0,68

Index of agreement V comp. = 0,64 Index of agreement U comp. = 0,32

Index of agreement V comp. = 0,40

CONCLUSIONS

• Delft3D system was successfully applied at the study area and proved to be a rugged tool, able to perform the coupling with HYCOM;

• Without using HYCOM results the system was not able to represent the circulation pattern of the area;

• The coupling between the numerical grids using domain decomposition technique solved properly the circulation dynamic at the boundaries we used a lower resolution (outside the bay, where there are HYCOM results) and at the study area we used a higher resolution (2nd grid).

Eduardo Yassuda

Eduardo.yassuda@tetratech.com

Clarissa Brelinger De Luca

Clarissa.deluca@tetratech.com

Maria Fernanda Mendes Fiedler

Fernanda.fiedler@tetratech.com

TETRA TECH BRASIL

Engenharia Costeira & Oceanografia

Tel: +55 11 3095-5050

Rua Fidalga, 711 | São Paulo, SP 05432-070 | www.tetratech.com

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