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Response of west Indian coastal regions and Kavaratti lagoon to the November-2009 tropical cyclone Phyan

DRS at CSIR-National Institute of Oceanography

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Title Response of west Indian coastal regions and Kavaratti lagoon to the November-2009 tropical cyclone Phyan
 
Creator Joseph, A.
Desai, R.G.P.
Mehra, P.
SanilKumar, V.
Radhakrishnan, K.V.
VijayKumar, K.
AshokKumar, K.
Agarwadekar, Y.
Bhat, U.G.
Luis, R.
Rivankar, P.
Viegas, B.
 
Subject Cyclonic storm
Storm surges
cyclones
Indian Ocean
surface wave
 
Description Response of the coastal regions of eastern Arabian Sea (AS) and Kavaratti Island lagoon in the AS to the tropical cyclonic storm `Phyan’, which developed in winter in the south-eastern AS and swept northward along the eastern AS during 9–12 November 2009 until its landfall at the northwest coast of India, is examined based on in situ and satellite-derived measurements. Wind was predominantly south/south-westerly and the maximum wind speed (U sub (10)) of approx.16 meter per second occurred at Kavaratti Island region followed by approx.8 meter per second at Dwarka (Gujarat) and approx.7 meter per second at Diu (located south of Dwarka) as well as two southwest Indian coastal locations (Mangalore and Malpe). All other west Indian coastal sites recorded maximum wind speed of approx.5–6 meter per second. Gust factor (i.e., gust-to-speed ratio) during peak storm event was highly variable with respect to topography, with steep hilly stations (Karwar and Ratnagiri) and proximate thick and tall vegetation-rich site (Kochi) exhibiting large values (approx.6), whereas Island station (Kavaratti) exhibiting approx.1 (indicating consistently steady wind). Rainfall in association with Phyan was temporally scattered, with the highest 24-h accumulated precipitation (approx.60 mm) at Karwar and approx.45 mm at several other west Indian coastal sites. Impact of Phyan on the west Indian coastal regions was manifested in terms of intensified significant waves (approx.2.2 m at Karwar and Panaji), sea surface cooling (approx.5 degree celsius at Calicut), and moderate surge (approx.50 cm at Verem, Goa). The surface waves were south-westerly and the peak wave period (T sub (p)) shortened from approx.10–17 s to approx.5–10 s during Phyan, indicating their transition from the long-period `swell’ to the short-period `sea’. Reduction in the spread of the mean wave period (T sub (z)) from approx.5–10 s to a steady period of approx.6 s was another manifestation of the influence of the cyclone on the surface wave field. Several factors such as (1) water piling-up at the coast supported by south/south-westerly wind and seaward flow of the excess water in the rivers due to heavy rains, (2) reduction of piling-up at the coast, supported by the upstream penetration of seawater into the rivers, and (3) possible interaction of upstream flow with river run-off, together resulted in the observed moderate surge at the west Indian coast. Despite the intense wind forcing, Kavaratti Island lagoon experienced insignificantly weak surge (approx.7 cm) because of lack of river influx and absence of a sufficiently large land boundary required for the generation and sustenance of wave/wind-driven water mass piling-up at the land–sea interface
 
Date 2011-05-11T05:11:33Z
2011-05-11T05:11:33Z
2011
 
Type Journal Article
 
Identifier Natural Hazards, vol.57(2); 2011; 293-312
http://drs.nio.org/drs/handle/2264/3851
 
Language en
 
Rights An edited version of this paper was published by Springer. This paper is for R & D purpose and Copyright [2011] Springer
 
Publisher Springer