Current Science

R. Venkatesan ¹, Simi Mathew ¹, J. Vimala ¹, G. Latha ¹, M. Arul Muthiah ¹, S. Ramasundaram ¹, R. Sundar ¹, R. Lavanya ¹, M. A. Atmanand ¹

Affiliations
1 National Institute of Ocean Technology, Velachery–Tambaram Main Road, Pallikaranai P.O., Chennai 600 100, IN

Abstract

The moored buoy network deployed in the Bay of Bengal played a critical role in the collection and transmission of surface meteorological and oceanographic conditions in real time through satellite telemetry, enabling constant monitoring of the cyclone Phailin. It is the first report of in situ timeseries measurement of a very low pressure taken during cyclones in the northern Indian Ocean. The BD10 buoy recorded a minimum atmospheric pressure of 920 hPa, which happened to be within the eye of the cyclone. This article presents an account of important changes that were observed in the surface meteorological and oceanographic parameters under the influence of the very severe cyclonic storm Phailin. An attempt has been made to understand the role of stratification in intensifying the cyclone Phailin in comparison with the cyclone Lehar which weakened in the ocean itself, based on subsurface data from the moored buoys which were on the track of the respective cyclones. Both the cyclones traversed across the Bay of Bengal in a similar way and the buoys were very close to the cyclone track withstood the rough sea conditions during the storms with their specially designed body. The BD09 buoy which happened to be on the right side of the track of cyclone Phailin moved in a circular path as a result of the inertial oscillation forced by the strong cyclonic winds.

Keywords

Cyclonic Storm, Met-Ocean Parameters, Moored Buoy, Real-Time Observations.

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Suchandra A. Bhowmick ¹, Neeraj Agarwal ¹, Rashmi Sharma ¹, R. Sundar ², R. Venkatesan ², C. Anoopa Prasad ¹, K. N. Navaneeth ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organization, Ahmedabad 380 015, IN
2 National Institute of Ocean Technology, MOES, Chennai 600 100, IN

Abstract

Amphan, a category-5 tropical cyclone, originated over Bay of Bengal (BoB) and had a landfall in West Bengal, India on 20 May, causing havoc in the region. In this study, in-situ buoy and various satellite measurements are used to analyse the ocean condition before and after the storm, primarily from the air–sea interaction perspective. Widespread anomalous warming was observed in BoB before the event, due to high net surface insolation received by the ocean. The warm SST anomalies in the central BoB were coincident with anti-cyclonic warm core eddies, implying availability of higher oceanic heat content. Observations from BD13 buoy, close to the cyclone track showed heating of the overlying atmosphere due to this ocean warming. Strong surface cooling was observed after passage of the cyclone due to wind induced upper-ocean mixing that is stimulated by low stratification in BoB.

Keywords

Air–Sea Interaction, Oceanic Conditions, Satellite and In situ Observations, Tropical Cyclones.

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