Economical use of coastal ocean and shelf seas’ natural resources along the Brazilian coastline has increased in the last fifty years, especially the activities related to the Oil & Gas industry. Understanding the dynamics of the coastal ocean and shelf seas is important to support the policies for exploration of these areas. Ocean modeling with data assimilation is an important tool to help understanding ocean dynamics. This work is focused on the initial results obtained with the regional application of the HYbrid Coordinate Ocean Model (HYCOM) developed at the Oceanographic Modeling and Research Network (REMO). The HYCOM-CHM/REMO is an operational ocean forecast model that includes tide forcing from its boundaries and imposes Sea Surface Height (SSH) using the Cooper & Haines (1996) method. This methodology used 3 nested grids (1/40,1/120 and 1/240) and high resolution bathymetry from the Brazilian Navy nautical charts database. It was also used TPXO 7.2 model to predict tides in the boundaries. Tide amplitudes and velocities were imposed at the N,S and E boundaries, using Clamped condition (see top center box). Then, 8 tidal constituents were extracted from each grid point after a long run (Feb. 2nd 2010 to Oct. 29th 2010). With this, it was possible to predict astronomical tides for each grid point. Innovations to be imposed using Cooper & Haines(C&H) were obtained subtracting the model Sea Surface Height (SSH) from the sum of the tide height to the external SSH .

Implementation of tides and Cooper & Haines method in HYCOM-CHM/REMO regional application

Raquel Leite Mello1, João Bosco Rodrigues Alvarenga1 and Cesar Reinert Bulhões de Morais2

Summary HYCOM-CHM-REMO: The Southwest Atlantic

Hybrid Coordinate Ocean Model

1 Oceanographic Modeling and Research - Brazilian Navy Hydrographic Center (REMO-CHM) Rua Barão de Jaceguai, s/n - Ponta da Areia – Niterói- RJ- Brazil CEP 24048-900

+55 21 2189-3612 – raquellm.mello@smm.mil.br

2 Brazilian Navy Hydrographic Center (CHM) Rua Barão de Jaceguai, s/n - Ponta da Areia – Niterói- RJ- Brazil CEP 24048-900

+55 21 2189-3609 – reinert@smm.mil.br

COOPER, M. & HAINES, K. 1996. Altimetric assimilation with water property conservation. Journal of Geophysical Research, 101, 1059-1077.

CHASSIGNET, E. P. ; HURLBURT, H. E. ; METZGER, E. J. ; SMEDSTAD, O. M.; CUMMINGS, J. A.; HALLIWELL, G. R.; BLECK, R. ; BARAILLE, R.; WALLCRAFT, A. J.; LOZANO, C.; TOLMAN, H. L.; SRINIVASAN, A.; HANKIN, S.; CORNILLON, P.; WEISBERG, R.; BARTH, A.; HE, R.; WERNER, F. & WILKIN, J., 2009. US GODAE: Global ocean prediction with the HYbrid Coordinate Ocean Model (HYCOM). Oceanography, 22:2:64–75, doi:10.5670/oceanog.2009.39.

TANAJURA, C. A. S. & BELYAEV K. P., 2002. On the oceanic impact of a data-assimilation method in a coupled ocean-land-atmosphere model. Ocean Dynamics, 52:123-132, DOI 10.1007/s10236-002-0013-8.

KOURAFALOU, V. H.; PENG, G.; KANG, H.; HOGAN, P. J.; SMEDSTAD, O. & WEISBERG, R. H., 2009. Evaluation of Global Ocean Data Assimilation Experiment products on South Florida nested simulations with the Hybrid Coordinate Ocean Model. Ocean Dynamics 59:47–66. DOI 10.1007/s10236-008-0160-7

MERRIELD, M. A.; HOLLOWAY, P. E. & JOHNSTON, T. M. S., 2001. The Generation of internal tides at the Hawaiian Ridge. Geophysical Research Letters. 28:4:559-562.

Results show that the method implied allowed SSH field innovations from global HYCOM, that do not include tides, to be coherent with those obtained from integrations without tides as boundary condition. Eddie features and meanders were well represented. The highest innovations were located in the shallow regions where satellite altimetry is not yet reliable.

Conclusion

References

Fig. 2: a) Sea Surface Height field resulting from addition of external HYCOM+NCODA/NRL’s SSH and predicted tide at 12GMT;

b) HYCOM-CHM/REMO’s Sea Surface Height at 12GMT.

Fig. 1: a) Tide Amplitude at 12GMT; b) Sea Surface Height (SSH) at 12GMT from HYCOM+NCODA/NRL.

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v int ( j) = vnest ( j) + vtide ( j)

pbar _ int ( j) = pbar _ nest ( j) +TH( j) × g

– internal grid velocity – external nesting velocity – predicted tide velocity Pbar_int – internal grid barotropic pressure Pbar_nest – nesting barotropic pressure TH – tide height g – gravity acceleration

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v int

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vnest

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vtideFig. 3: Sea Surface Height field difference to be imposed to the model using Cooper & Haines method.