A snapshot of internal waves and hydrodynamic instabilities in the southern Bay of Bengal

TitleA snapshot of internal waves and hydrodynamic instabilities in the southern Bay of Bengal
Publication TypeJournal Article
Year of Publication2016
AuthorsLozovatsky I., Wijesekera H., Jarosz E., Lilover M.J, Pirro A., Silver Z., Centurioni L, Fernando H.JS
JournalJournal of Geophysical Research-Oceans
Volume121
Pagination5898-5915
Date Published2016/08
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000386912700030
Keywordschina sea; crest; generation; heights; layer; model; monsoon; Shear; sri-lanka
Abstract

Measurements conducted in the southern Bay of Bengal (BoB) as a part of the ASIRI-EBoB Program portray the characteristics of high-frequency internal waves in the upper pycnocline as well as the velocity structure with episodic events of shear instability. A 20 h time series of CTD, ADCP, and acoustic backscatter profiles down to 150 m as well as temporal CTD measurements in the pycnocline at z=54 m were taken to the east of Sri Lanka. Internal waves of periods similar to 10-40 min were recorded at all depths below a shallow (similar to 20-30 m) surface mixed layer in the background of an 8 m amplitude internal tide. The absolute values of vertical displacements associated with high-frequency waves followed the Nakagami distribution with a median value of 2.1 m and a 95% quintile 6.5 m. The internal wave amplitudes are normally distributed. The tails of the distribution deviate from normality due to episodic high-amplitude displacements. The sporadic appearance of internal waves with amplitudes exceeding similar to 5 m usually coincided with patches of low Richardson numbers, pointing to local shear instability as a possible mechanism of internalwave- induced turbulence. The probability of shear instability in the summer BoB pycnocline based on an exponential distribution of the inverse Richardson number, however, appears to be relatively low, not exceeding 4% for Ri < 0.25 and about 10% for Ri < 0.36 (K-H billows). The probability of the generation of asymmetric breaking internal waves and Holmboe instabilities is above similar to 25%.

DOI10.1002/2016jc011697
Short TitleJ Geophys Res-Oceans
Student Publication: 
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