Tidal & wave characteristic of bay of bengal.

1. Tide and wave characteristics of
bay of Bengal
Name:Sadia Tasmin Isha
ID-B180602049
Department of Geography and Environment, Jagannath University,
Dhaka

2. Table content -
 Definition of tide
 Characteristic features
 Tide generating force
 Time of tides
 Tpes of tides
 Tide characteristic of bay of bengal
 Wave
 Wave characterized components
 Types and movement of sea waves
 Seasonal wave of bay of bengal
 Wave ddirection of bay of bengal
 Wave of bay of bengal

3.  There are different types of movements of ocean water under the
influence of different physical characteristics like temperature, salinity,
density,etc. Movements of ocean water are also affected by external
forces like the sun moon and the winds.
The major movements of the ocean water can be classified into 3
 wave
 Tides
 ocean currents
Waves and the ocean currents are horizontal movements of the ocean waters
while the tide is a kind of vertical movement of the ocean water.

4. Tide
 The Rise and fall of sea water due to gravitational forces (centrepetal) of the sun and the
moon are called tides .
 “Tides are waves with very long wavelengths- much longer than ordinary wind waves -
that cause sea level to rise and fall with extraordinary regularity. In fact ,tides are the
most uniformly varying phenomenon in the ocean.”

P.R. Pinet (2000)
 The alternate rising and falling of the sea, usually twice in each Lunar day at a particular
place due to the attraction of the moon and sun .

5. Tide
 Tide at the periodical rise and fall of the Sea level once or twice a
day caused by the combined effects of the gravitational force
exerted by the sun the moon and the rotation of the earth.
 They are a vertical movement of waters and are different from
movements of ocean water caused by metrological effects like
the winds and atmospheric pressure changes.
 Note: the water movements which are caused by the metrological
effects like the side are called as surges and they are not regular
like tides.
 The moon’s ggravitational pull to a great extent is the major
causes of the ooccurrence of Tides (the moon’s gravitational
attraction is more effective on the earth then that of the sun)
 Sun's gravitational pull and the centrifugal force due to the
rotation of the earth are the other forces which act along with the
moons gravitational pull.

6. Tides characteristic features
The ocean Tides are characterized by the following typical features-
 Tides are single wave phenomenon which covers the entire Ocean
basin
 Tides are shallow water waves but with very long wavelength even in
the deep ocean basin .
 Tides are differentiated from wind-driven sea waves with respect to
wavelength, wave height, mode of origin etc.
 Tides are low waves but with high energy, while se waves are high
waves with low energy.
 The tidal wave height is called tidal range.On the basis of height
tidal range is divided into the following three categories :
1. Mcrotidal range, height( wave height) less than 2m
2. Mesotidal range, wave height between 2 to 4m
3. Macrotidal range, wave height more than 4m

7. The origin of Tides in the ocean is
primarily concerned with the
gravitational forces of the sun and the
moon.It may be pointed out that the
Earth rotates from west to east and
revolves around the sun following an
elliptical Orbit.

8. Time of Tides
Lunar day (also known as a "tidal day") is the time it takes for a specific site on
the Earth to rotate from an exact point under the moon to the same point under the
moon. Unlike a solar day, however, a lunar day is 24 hours and 50 minutes. The
lunar day is 50 minutes longer than a solar day because the moon revolves around
the Earth in the same direction that the Earth rotates around its axis. So, it takes
the Earth an extra 50 minutes to “catch up” to the moon.
Because the Earth rotates through two tidal “bulges” every lunar day, coastal areas
experience two high and two low tides every 24 hours and 50 minutes. High tides
occur 12 hours and 25 minutes apart. It takes six hours and 12.5 minutes for the
water at the shore to go from high to low, or from low to high.

9. Types of tides
The oceanic tides are caused due to tide producing force of the sun and the moon
.There is a lot of temporal and special variation in the tide producing forces
because of different positions of the sun and the moon with the earth.
A.Tides based on the Frequency
 Semi –diurnal tide: they are the most common tidal pattern, featuring 2
high tides and two low Tides each day .
 Diurnal Tides :only one high Tides and one low Tide each Day.
 Mixed tide: Tides having variations in Heights are known as mixed Tides.
the generally occur along the West Coast of North America.

10. B.Tides based on the sun, the moon
and the earth’s positions
 Spring tides
 Neep Tides
 Tropical and equatorial tides
 Apogean and perigean tides
 Diurnal and semi-diurnal tides
 Equinoctial spring tides
 Direct and indirect tides(zenithal and nadir tides)

11. Tide charecteristic of Bay of Bengal
 A vertically integrated 2D numerical model was developed for the simulation of major
tidal constituents (M2, S2, N2, K1 and O1) in the Bay of Bengal. The bathymetry for
the model domain was derived from an improved ETOPO5 dataset prepared in our
earlier work. The simulated tidal elevations showed good agreement with the hourly
tide gauge observations at Paradip, Visakhapatnam, and Chennai. The amplitudes and
phases of M2, S2, K1, and O1 at the coastal stations, obtained from harmonic analysis
of simulated tides, were found to agree well with those obtained from Admiralty Tide
Tables with the RMS misfit 9.2, 5.6, 2.9 and 3.1 cm, respectively. In the Bay of
Bengal, semi-diurnal tides (M2, S2, and N2) attain highest amplitudes (180, 80, 30
cm, respectively) in the Gulf of Martaban while amplitudes of diurnal tides (K1, O1)
reaches maximum (20, 12 cm, respectively) in the Malacca Strait. The continental
shelf in the head bay and along the southern coast of Myanmar is about 200 km wide
and the amplitudes of semi-diurnal tides are doubled in these regions while the diurnal
tides amplify only marginally, which is consistent with Clarke and Battisti theory.

12.  In the north eastern end of the head bay and
the Gulf of Martaban, the geometrical
configuration of the coastline, in addition to
the wide continental shelf, could contribute
to the amplification of both semi-diurnal
and diurnal constituents. In the Malacca
Strait, the amplitudes of both semi-diurnal
and diurnal tides are found to increase
gradually from the northern end to the
2.5°N and decreases towards southern
boundary. The co-tidal and co-range charts
of M2 and S2 tidal constituents also show
the presence of two degenerate
amphidromic points in the head bay. A
virtual amphidromic point for M2 is
identified in the Malacca Strait.

13.  Tides the semi-diurnal type of tides, ie
two high and two low tides during the
period of 24 hours and 52 minutes. The
highest tide is seen where the influence
of bottom relief and the configuration
of the coast are prominent, ie in shallow
water and in the Bay and ESTUARY. The
average height of tidal waves at the
coast of Sri Lanka is 0.7m and in the
deltaic coast of the Ganges it is 4.71m.
In the Bay of Bengal tidal currents
specially develop in the mouths of the
rivers, like the Hooghly and
the MEGHNA.

14. Wave components and characteristics
 The oceans surfaces are never claim and smooth rather they are uneven,
irregular, rough and restless. Thus, sea waves have great energy potential for
feature generations. This is why is H.V. Thurman and A.P. Trujillo (1999) have
defined sea waves in terms in terms of energy level as follows:
“Waves are moving energy travelling along the interface between
ocean and atmosphere ,often transferring energy from a strom for out
at see over distances of several thousand kilometers”
(Thurman and Trujillo,1999)

15. The waves are characterized by
the following components
 Wave crest
 Wave troughs
 Still water level
 Wave height
 Wavelength
 Wave steepness
 Wave period
 Wave frequency
 Wave celerity
 Wave trains
Fig-Patterns and components of sea waves

16. Seasonal wave
 Wave data reported in the Indian Daily Weather Reports for the period 1960-64
have been used to evaluate seasonal wave characteristics for each 2-degree
square areas of the Bay of Bengal. These results are presented in the form of
charts. The maxima of the average heights in the Bay of Bengal (3.1 m) have
been observed during the monsoon season even though the number of cyclone
and depression days were maximum in May and November, respectively in the
Bay of Bengal. The most prominent period of waves in all seasons the regions
was '5 or less than 5' seconds

17. waves direction of Bay of Bengal
 For the Bay of Bengal region, the daily
climatology of significant wave height
ranges from a minimum of 0.5 m to a
maximum of 2.5 m, comparatively smaller
than that in the Arabian Sea. Predominant
wave heights ranging between 1 and 1.5 m
occur in almost 38.9% of the total waves in a
year (Vethamony et al., 2000).Jan 21, 2016

18. Wave of bay of Bengal
 Spectral wave characteristics were studied based on waves measured for 1 year
during 2010 off Gangavaram, Bay of Bengal. Maximum wave height of 5.2 m
was observed on 19 May 2010 due to the influence of cyclonic storm LAILA.
The wave spectrum was single-peaked during 57 % of the time and the double-
peaked spectrum observed was mainly swell-dominated. Low-frequency waves
(0.05–0.15 Hz) were predominantly from 150° to 180°, whereas high-
frequency waves (>0.15 Hz) during November–January were mainly from 90°
to 120°, and during July and August from 180° to 210°. Annual average
significant wave height was similar to the value (1 m) observed in the eastern
Arabian Sea.