Informatics Publishing Limited

T. M. Balakrishnan Nair ¹, V. Ramaswamy ¹, G. Parthiban ¹, R. Shankar ²

Affiliations
1 National Institute of Oceanography, Dona Paula, Goa - 403 004, IN
2 Department of Marine Geology, Mangalore University, Mangalagangotri - 574 199, IN

Abstract

Particle fluxes were measured using six time-series sediment traps at three sites in the western (16°20' N; 60°30' E), central (14°31' N; 64°46' E) and eastern (15°31' N; 68°43' E) Arabian Sea. Trap deployment depths were between 900 and 3000 m and collection period was from December 1992 to February 1994.

Annual particle fluxes showed an east-west trend with minimum fluxes (22.25 gm^-2) in the eastern Arabian Sea and maximum fluxes (69.81 g m^-2) in the western Arabian Sea. Carbonates, contributed mainly by foraminifers and coccolithophorids, are the dominant component in all the traps. Opal fluxes were maximum in the western Arabian Sea. At all the locations, lithogenic percentages increased with depth whereas organic carbon percentages decreased. Particle flux patterns show a strong seasonality with peak fluxes during the southwest (SW) monsoon (June to September). Relatively high fluxes were also observed during the northeast (NE) monsoon (December to February).

In the western Arabian Sea, particle fluxes are dominated mainly by carbonates during the early SW monsoon but by biogenic silica during the fate SW monsoon. The increase in particle fluxes during the early SW monsoon is related to variations in the mixed layer depth which, in turn, is controlled by the strength of the Findtater Jet and the curl of the wind stress. The increase in biogenic silica fluxes during the late SW monsoon is related to the advection of nutrient-rich water from the Oman and Somali upwelling areas. In the eastern Arabian Sea, particle fluxes are high during the NE monsoon due to the effects of winter cooling.

Keywords

Oceanography, Particle Flux, Sediment Trap, Sea Surface Temperature, Arabian Sea.

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T. M. Balakrishnan Nair ¹, P. G. Remya ¹, R. Harikumar ¹, K. G. Sandhya ¹, P. Sirisha ¹, K. Srinivas ¹, C. Nagaraju ¹, Arun Nherakkol ¹, B. Krishna Prasad ¹, C. Jeyakumar ¹, K. Kaviyazhahu ¹, N. K. Hithin ¹, Rakhi Kumari ¹, V. Sanil Kumar ², M. Ramesh Kumar ¹, S. S. C. Shenoi ¹, Shailesh Nayak ³

Affiliations
1 Information Services and Ocean Sciences Group, ESSO-Indian National Centre for Ocean Information Services, 'Ocean Valley', Pragathi Nagar (BO), Nizampet (SO), Hyderabad 500 090, IN
2 CSIR-National Institute of Oceanography, Dona Paula, Goa 403 004, IN
3 Earth System Science Organization, New Delhi 110 003, IN

Abstract

Wave fields, both measured and forecast during the very severe cyclone Phailin, are discussed in this communication. Waves having maximum height of 13.54 m were recorded at Gopalpur, the landfall point of the cyclone. The forecast and observed significant wave heights matched well at Gopalpur with correlation coefficient of 0.98, RMS e rror of 0.35 m and scatter index of 14%. Forecasts were also validated in the open ocean and found to be reliable (scatter index < 15%). The study also revealed the presence of Southern Ocean swells with a peak period of 20-22 sec hitting Gopalpur coast along with the cyclone-generated waves.

Keywords

Buoys, Phailin, Tropical Cyclone, Swell, Wave Forecast.

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R. Harikumar ¹, T. M. Balakrishnan Nair ¹, B. M. Rao ¹, Rajendra Prasad ², P. Ramakrishna Phani ¹, C. Nagaraju ¹, M. Ramesh Kumar ¹, C. Jeyakumar ¹, S. S. C. Shenoi ¹, Shailesh Nayak ³

Affiliations
1 ESSO-Indian National Centre for Ocean Information Services, Hyderabad 500 090, IN
2 Andhra University, Visakhapatnam 530 003, IN
3 Earth System Science Organisation, New Delhi 110 003, IN

Abstract

Ocean-met observations from INCOIS real-time automatic weather station on-board a ship RV Kaustubh served as strong ground truth for satellite- and modelderived forecasts during the very severe cyclonic storm Hudhud, which made a landfall at Visakhapatnam, India. The ship recorded maximum wind speed of 204 km/h (with a minimum central pressure of 945 hPa), which is the highest (lowest) ever instrumentally recorded value at a location on the Indian coastline during any cyclone. Though the global model forecasts of wind fields have shown good agreement inland, they failed in representing the reality along the coasts. Variation in wind energy from ocean towards inland suggests that it is attenuated exponentially inland (the maximum wind power density had reduced by 93,406 W/m² at Anakapalle (~25 km) compared to the ocean, and by 7022 W/m² at Chintapalle (~100 km inland) compared to Anakapalle). The present study reinforces the significance of having realtime near-shore ocean-met observations, and their operational usage for evaluation (assimilation) of (into) ocean-met forecast models in realtime.

Keywords

Automatic Weather Stations, Bias-Corrected Wind Forecasts, Forecast Models, Tropical Cyclones, Shipbased Observations, Wind Power Density.

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