Study of internal wave characteristics off northwest Bay of Bengal using synthetic aperture radar
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Study of internal wave characteristics off northwest Bay of Bengal using synthetic aperture radar Suryanarayana Acharyulu Phaniharam1 · Venkateswarlu Chintam1 · Gireesh Baggu1 · Venkata Siva Rama Prasad Koneru1 Received: 18 December 2019 / Accepted: 29 August 2020 © Springer Nature B.V. 2020
Abstract Internal solitary waves (IWs) in the northwest Bay of Bengal were studied using ENVISAT ASAR imageries. Simultaneous in situ observations were also carried out to study the characteristics of the internal waves. Internal wave features have often been observed over the ocean area between 18.5°–19.5° N and 84.5°–85.5° E. The direction of propagation of IWs is generally toward the coast with wavelengths ranging from 0.4 to 1.1 km. The phase speeds of the IWs vary from 0.12 to 1.3 m/s. Internal wave amplitudes computed using Korteweg and de Vries model show good agreement with in situ data. Based on their direction of propagation and time series analysis, IWs generated were found to be of tidal forcing origin over local topographic features. IWs of different types like wave packets or wave trains and single solitons of weak manifestations were observed depending on the phase and the tidal amplitude as well as the stratification of the ocean, which in turn vary due to the dynamic and complex nature of Bay of Bengal, as it experiences strong monsoon winds and low pressure systems with calm weather in between them. The internal waves are often observed during non-monsoon period over this region. During monsoon period, continuous vertical mixing takes place due to strong winds causing unfavorable conditions for IW formation and so the observation of IWs during monsoons is rather rare. Keywords Internal solitary waves · Monsoon · Stratification · Tidal amplitude · Vertical mixing
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1106 9-020-04280-6) contains supplementary material, which is available to authorized users. * Suryanarayana Acharyulu Phaniharam [email protected] Venkateswarlu Chintam [email protected] Gireesh Baggu [email protected] Venkata Siva Rama Prasad Koneru [email protected] 1
Department of Meteorology and Oceanography, Andhra University, Visakhapatnam, Andhra Pradesh 530003, India
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1 Introduction Internal solitary waves are generally observed in stable stratified waters with well-developed pycnocline, and they propagate mainly along the pycnocline in shallow waters (Dokken et al. 2001). Their generation and propagation play an important role in the study of nutrient distribution, acoustic propagation and submarine navigation (Li et al. 2008). Generation of internal waves (IWs) occurs in several ways. Although they generate through other mechanisms such as frontal boundaries and special wind conditions, they are most commonly generated by tidal flow over underwater obstacles such as sills, continental shelves and troughs (Dokken et al. 2001; Joshi et al. 2017; Prasad and Rajasekhar 2011). I
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