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Tidal asymmetry and characteristics of tides at the head of the Bay of Bengal
Author(s) -
Rose Linta,
Bhaskaran Prasad K.
Publication year - 2017
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.3122
Subject(s) - bay , geology , water level , estuary , tidal irrigation , oceanography , discharge , dominance (genetics) , flood myth , waves and shallow water , environmental science , geography , drainage basin , biochemistry , chemistry , cartography , archaeology , gene
The Advanced Circulation (ADCIRC) hydrodynamic model has been utilized to report on the tidal characteristics and asymmetry for the head Bay of Bengal region and validated against limited available observations. The study investigates spatial and temporal variability of tides using the techniques of wavelet and time‐series analysis at various locations, with special emphasis on major rivers Hooghly and Meghna. Tidal asymmetry with flood dominance was found to increase steadily upstream due to nonlinear energy transfer from principal components to higher harmonics. The low water‐levels were increased upstream implying that attenuation by frictional dissipation dominates, over amplification due to channel convergence. Shallow water and mild depth gradient were discerned to be requisite factors in generating long‐period nonlinear tides, and they have been found to amplify in concave deltaic regions where tides are funnelled. Additionally, spring‐neap variations in bottom friction caused low water‐level to occur during neap rather than spring tide along upper reaches of the tide‐dominated rivers, leading to the formation of a forced fortnightly tide. It is notable that a fortnightly tidal component manifests itself even in the absence of river discharge input, contrary to common conception, indicating that shallow water interaction and coastal geomorphology alone can cause fortnightly dominance in tidal rivers. A weak monthly tidal component was also observed in the tidal rivers and the study proposes that it originates due to frictional modulation of monthly lunar tides. Dominance and amplification of long‐period nonlinear tides in wide, convergent rivers may be attributed to resonance effects, in addition to effects of shoaling topography and convergent channel geometry.