Estimation and prediction of the upper ocean circulation in the Bay of Bengal

Abstract Composites of Florida State University winds (1970–99) for four different climate scenarios are used to force an Indian Ocean model. In addition to the mean climatology, the cases include La Niña, El Niño, and the Indian Ocean dipole (IOD). The differences in upper-ocean water mass exchanges between the Arabian Sea and the Bay of Bengal are investigated and show that, during El Niño and IOD years, the average clockwise Indian Ocean circulation is intensified, while it is weakened during La Niña years. As a consequence, high-salinity water export from the Arabian Sea into the Bay of Bengal is enhanced during El Niño and IOD years, while transport of low-salinity waters from the Bay of Bengal into the Arabian Sea is enhanced during La Niña years. This provides a venue for interannual salinity variations in the northern Indian Ocean.

Download Full-text

The impact of ocean-wave coupling on the upper ocean circulation during storm events

10.1002/essoar.10506457.1 ◽

2021 ◽

Cited By ~ 1

Author(s):

Diego Bruciaferri ◽

Marina Tonani ◽

Huw Lewis ◽

John Siddorn ◽

Andrew Saulter ◽

...

Keyword(s):

Ocean Circulation ◽

Ocean Wave ◽

Upper Ocean ◽

Storm Events ◽

Wave Coupling ◽

The Impact

Download Full-text

Study of the air-sea interactions at the mesoscale: the SEMAPHORE experiment

Annales Geophysicae ◽

10.1007/s00585-996-0986-6 ◽

1996 ◽

Vol 14 (9) ◽

pp. 986-1015 ◽

Cited By ~ 50

Author(s):

L. Eymard ◽

S. Planton ◽

P. Durand ◽

C. Le Visage ◽

P. Y. Le Traon ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Ocean Circulation ◽

Wave Model ◽

Heat Fluxes ◽

Sea Surface ◽

Upper Ocean ◽

Test Model ◽

Model Simulations ◽

Drifting Buoys

Abstract. The SEMAPHORE (Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale) experiment has been conducted from June to November 1993 in the Northeast Atlantic between the Azores and Madeira. It was centered on the study of the mesoscale ocean circulation and air-sea interactions. The experimental investigation was achieved at the mesoscale using moorings, floats, and ship hydrological survey, and at a smaller scale by one dedicated ship, two instrumented aircraft, and surface drifting buoys, for one and a half month in October-November (IOP: intense observing period). Observations from meteorological operational satellites as well as spaceborne microwave sensors were used in complement. The main studies undertaken concern the mesoscale ocean, the upper ocean, the atmospheric boundary layer, and the sea surface, and first results are presented for the various topics. From data analysis and model simulations, the main characteristics of the ocean circulation were deduced, showing the close relationship between the Azores front meander and the occurrence of Mediterranean water lenses (meddies), and the shift between the Azores current frontal signature at the surface and within the thermocline. Using drifting buoys and ship data in the upper ocean, the gap between the scales of the atmospheric forcing and the oceanic variability was made evident. A 2 °C decrease and a 40-m deepening of the mixed layer were measured within the IOP, associated with a heating loss of about 100 W m-2. This evolution was shown to be strongly connected to the occurrence of storms at the beginning and the end of October. Above the surface, turbulent measurements from ship and aircraft were analyzed across the surface thermal front, showing a 30% difference in heat fluxes between both sides during a 4-day period, and the respective contributions of the wind and the surface temperature were evaluated. The classical momentum flux bulk parameterization was found to fail in low wind and unstable conditions. Finally, the sea surface was investigated using airborne and satellite radars and wave buoys. A wave model, operationally used, was found to get better results compared with radar and wave-buoy measurements, when initialized using an improved wind field, obtained by assimilating satellite and buoy wind data in a meteorological model. A detailed analysis of a 2-day period showed that the swell component, propagating from a far source area, is underestimated in the wave model. A data base has been created, containing all experimental measurements. It will allow us to pursue the interpretation of observations and to test model simulations in the ocean, at the surface and in the atmospheric boundary layer, and to investigate the ocean-atmosphere coupling at the local and mesoscales.

Download Full-text

UPPER OCEAN VARIABILITY IN THE BAY OF BENGAL DURING 2006 IOD

Advances in Geosciences ◽

10.1142/9789812836168_0014 ◽

2009 ◽

pp. 197-211

Author(s):

P. SWAPNA ◽

N. BAHULAYAN ◽

N. A. DIANSKY

Keyword(s):

Bay Of Bengal ◽

Upper Ocean ◽

Ocean Variability

Download Full-text

Simulating the upper ocean circulation on the belize shelf: An application of a triply nested-grid ocean circulation model

Journal of Ocean University of China ◽

10.1007/s11802-005-0052-0 ◽

2005 ◽

Vol 4 (4) ◽

pp. 315-328 ◽

Cited By ~ 2

Author(s):

Jinyu Sheng ◽

Liqun Tang ◽

Liang Wang

Keyword(s):

Ocean Circulation ◽

Circulation Model ◽

Upper Ocean ◽

Ocean Circulation Model ◽

Nested Grid

Download Full-text

Marginal Sea Overflows and the Upper Ocean Interaction

Journal of Physical Oceanography ◽

10.1175/2008jpo3934.1 ◽

2009 ◽

Vol 39 (2) ◽

pp. 387-403 ◽

Cited By ~ 13

Author(s):

Shinichiro Kida ◽

Jiayan Yang ◽

James F. Price

Keyword(s):

Ocean Circulation ◽

Potential Vorticity ◽

Baroclinic Instability ◽

Upper Ocean ◽

Marginal Sea ◽

The Mediterranean ◽

The Difference ◽

Set Up ◽

Numerical Model Experiments ◽

Gyre Circulation

Abstract Marginal sea overflows and the overlying upper ocean are coupled in the vertical by two distinct mechanisms—by an interfacial mass flux from the upper ocean to the overflow layer that accompanies entrainment and by a divergent eddy flux associated with baroclinic instability. Because both mechanisms tend to be localized in space, the resulting upper ocean circulation can be characterized as a β plume for which the relevant background potential vorticity is set by the slope of the topography, that is, a topographic β plume. The entrainment-driven topographic β plume consists of a single gyre that is aligned along isobaths. The circulation is cyclonic within the upper ocean (water columns are stretched). The transport within one branch of the topographic β plume may exceed the entrainment flux by a factor of 2 or more. Overflows are likely to be baroclinically unstable, especially near the strait. This creates eddy variability in both the upper ocean and overflow layers and a flux of momentum and energy in the vertical. In the time mean, the eddies accompanying baroclinic instability set up a double-gyre circulation in the upper ocean, an eddy-driven topographic β plume. In regions where baroclinic instability is growing, the momentum flux from the overflow into the upper ocean acts as a drag on the overflow and causes the overflow to descend the slope at a steeper angle than what would arise from bottom friction alone. Numerical model experiments suggest that the Faroe Bank Channel overflow should be the most prominent example of an eddy-driven topographic β plume and that the resulting upper-layer transport should be comparable to that of the overflow. The overflow-layer eddies that accompany baroclinic instability are analogous to those observed in moored array data. In contrast, the upper layer of the Mediterranean overflow is likely to be dominated more by an entrainment-driven topographic β plume. The difference arises because entrainment occurs at a much shallower location for the Mediterranean case and the background potential vorticity gradient of the upper ocean is much larger.

Download Full-text

Response of the Salinity-Stratified Bay of Bengal to Cyclone Phailin

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0051.1 ◽

2019 ◽

Vol 49 (5) ◽

pp. 1121-1140 ◽

Cited By ~ 10

Author(s):

Dipanjan Chaudhuri ◽

Debasis Sengupta ◽

Eric D’Asaro ◽

R. Venkatesan ◽

M. Ravichandran

Keyword(s):

Barrier Layer ◽

Bay Of Bengal ◽

Sea Surface ◽

Density Stratification ◽

Upper Ocean ◽

Dimensional Model ◽

Cyclone Track ◽

Surface Salinity ◽

Near Surface ◽

One Dimensional

AbstractCyclone Phailin, which developed over the Bay of Bengal in October 2013, was one of the strongest tropical cyclones to make landfall in India. We study the response of the salinity-stratified north Bay of Bengal to Cyclone Phailin with the help of hourly observations from three open-ocean moorings 200 km from the cyclone track, a mooring close to the cyclone track, daily sea surface salinity (SSS) from Aquarius, and a one-dimensional model. Before the arrival of Phailin, moored observations showed a shallow layer of low-salinity water lying above a deep, warm “barrier” layer. As the winds strengthened, upper-ocean mixing due to enhanced vertical shear of storm-generated currents led to a rapid increase of near-surface salinity. Sea surface temperature (SST) cooled very little, however, because the prestorm subsurface ocean was warm. Aquarius SSS increased by 1.5–3 psu over an area of nearly one million square kilometers in the north Bay of Bengal. A one-dimensional model, with initial conditions and surface forcing based on moored observations, shows that cyclone winds rapidly eroded the shallow, salinity-dominated density stratification and mixed the upper ocean to 40–50-m depth, consistent with observations. Model sensitivity experiments indicate that changes in ocean mixed layer temperature in response to Cyclone Phailin are small. A nearly isothermal, salinity-stratified barrier layer in the prestorm upper ocean has two effects. First, near-surface density stratification reduces the depth of vertical mixing. Second, mixing is confined to the nearly isothermal layer, resulting in little or no SST cooling.

Download Full-text