Observations of long-period waves in the nearshore waters of central west coast of India during the fall inter-monsoon period

Abstract. Wave data collected off Ratnagiri, west coast of India during 1 May 2010 to 30 April 2012 is used in the study. Seasonal and annual variation in wave data controlled by the local wind system such as sea breeze and land breeze, and remote wind generated long period waves observed along the west coast of India, is studied. Sea breeze plays an important role in determining the sea state during pre and post monsoon seasons and the maximum wave height is observed during peak hours of sea breeze at 15:00 UTC. Long period waves (peak period over 13 s) are observed mainly during the pre and the post monsoon season. Maximum peak period observed during the study is 22 s and is in the month of October. Long period waves observed during the south west monsoon period of 2011 are identified as swell propagated from the Southern Ocean with an estimated travelling time of 5–6 days. The swells reaching the Arabian Sea from the South Indian Ocean and Southern Ocean, due to storms during the pre and post monsoon periods will modify the near surface winds, due to the dominant wave induced wind regime. Energy spectrum of observed waves indicates onset and decline of strong south west monsoon winds. Convergence of energy-containing frequency bands corresponding to short period waves (Tp < 8 s) and long period waves (Tp > 13 s) to intermediate period waves (8 < Tp < 13 s) are observed at the end of the pre monsoon season; divergence is observed during the start of the post monsoon period from intermediate period waves to short period waves and long period waves. South west monsoon period is characterized by the energy corresponding to the frequency band of intermediate period waves along the west coast of India.

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Hydrography of the west coast of India during the pre-monsoon period of the year 1962. 1. Shelf waters of Maharashtra and southwest Sourashtra coasts

Deep Sea Research and Oceanographic Abstracts ◽

10.1016/0011-7471(76)91107-4 ◽

1966 ◽

Vol 13 (5) ◽

pp. 1052-1053

Keyword(s):

West Coast ◽

The West ◽

Monsoon Period ◽

West Coast Of India

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Does Evaporation over the Arabian Sea Play a Crucial Role in Moisture Transport across the West Coast of India during an Active Monsoon Period?

Monthly Weather Review ◽

10.1175/1520-0493(1988)116<0307:deotas>2.0.co;2 ◽

1988 ◽

Vol 116 (2) ◽

pp. 307-312 ◽

Cited By ~ 16

Author(s):

Y. Sadhuram ◽

M. R. Ramesh Kumar

Keyword(s):

West Coast ◽

Crucial Role ◽

Moisture Transport ◽

Arabian Sea ◽

The West ◽

Monsoon Period ◽

West Coast Of India

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Inter-annual variations in wave spectral characteristics at a location off the central west coast of India

Annales Geophysicae ◽

10.5194/angeo-33-159-2015 ◽

2015 ◽

Vol 33 (2) ◽

pp. 159-167 ◽

Cited By ~ 17

Author(s):

V. Sanil Kumar ◽

M. Anjali Nair

Keyword(s):

West Coast ◽

Spectral Characteristics ◽

Wave Spectrum ◽

Spectral Energy ◽

Monsoon Period ◽

West Coast Of India ◽

Annual Variations ◽

The Indian Ocean ◽

Wind Sea ◽

Two Peaks

Abstract. The inter-annual variations in wave spectrum are examined based on the wave data measured at 9 m water depth off the central west coast of India from 2009 to 2012 using a wave rider buoy. The temporal variation of the spectral energy density over a calendar year indicates similar variation in all the four years studied. The inter-annual variations in wave spectrum are observed in all months with larger variations during January to February, May and October to November due to the changes in wind-sea. The seasonal average wave spectrum during the monsoon (June–September) is single-peaked and the swell component is high in 2011 compared to other years. The annual averaged wave spectrum had higher peak energy during 2011 due to the higher spectral energy present during the monsoon period. During the non-monsoon period, two peaks are predominantly observed in the wave spectra; with the average peak at 0.07 Hz corresponding to the swells from the Indian Ocean and another at 0.17 Hz due to the local wind field.

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Spatial and temporal variations of wave energy in the nearshore waters of the central west coast of India

Annales Geophysicae ◽

10.5194/angeo-34-1197-2016 ◽

2016 ◽

Vol 34 (12) ◽

pp. 1197-1208 ◽

Cited By ~ 3

Author(s):

M. M. Amrutha ◽

V. Sanil Kumar

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Water Depth ◽

Wave Energy ◽

West Coast ◽

Temporal Variations ◽

Wave Power ◽

Monsoon Period ◽

West Coast Of India ◽

Water Depths

Abstract. Assessment of wave power potential at different water depths and time is required for identifying a wave power plant location. This study examines the variation in wave power off the central west coast of India at water depths of 30, 9 and 5 m based on waverider buoy measured wave data. The study shows a significant reduction ( ∼  10 to 27 %) in wave power at 9 m water depth compared to 30 m and the wave power available at 5 m water depth is 20 to 23 % less than that at 9 m. At 9 m depth, the seasonal mean value of the wave power varied from 1.6 kW m−1 in the post-monsoon period (ONDJ) to 15.2 kW m−1 in the Indian summer monsoon (JJAS) period. During the Indian summer monsoon period, the variation of wave power in a day is up to 32 kW m−1. At 9 m water depth, the mean annual wave power is 6 kW m−1 and interannual variations up to 19.3 % are observed during 2009–2014. High wave energy ( >  20 kW m−1) at the study area is essentially from the directional sector 245–270° and also 75 % of the total annual wave energy is from this narrow directional sector, which is advantageous while aligning the wave energy converter.

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Observational Evidence of Summer Shamal Swells along the West Coast of India*

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-12-00059.1 ◽

2013 ◽

Vol 30 (2) ◽

pp. 379-388 ◽

Cited By ~ 17

Author(s):

Johnson Glejin ◽

V. Sanil Kumar ◽

T. M. Balakrishnan Nair ◽

Jai Singh ◽

Prakash Mehra

Keyword(s):

West Coast ◽

Arabian Peninsula ◽

Indian Subcontinent ◽

Southwest Monsoon ◽

Sea Waves ◽

The West ◽

Monsoon Period ◽

West Coast Of India ◽

Wind Sea ◽

The Persian Gulf

Abstract Wave data collected off Ratnagiri, which is on the west coast of India, in 2010 and 2011 are used to examine the presence of the summer shamal swells. This study also aims to understand variations in wave characteristics and associated modifications in wind sea propagation at Ratnagiri. Wind data collected using an autonomous weather station (AWS), along with Advanced Scatterometer (ASCAT) and NCEP data, are used to identify the presence of summer shamal winds along the west coast of the Indian subcontinent and on the Arabian Peninsula. NCEP and ASCAT data indicate the presence of summer shamal winds over the Arabian Peninsula and northwesterly winds at Ratnagiri. This study identifies the presence of swells from the northwest that originate from the summer shamal winds in the Persian Gulf and that reach Ratnagiri during 30% of the summer shamal period. AWS data show the presence of northwest winds during May and southwest winds during the strong southwest monsoon period (June–August). Another important factor identified at Ratnagiri that is associated with the summer shamal events is the direction of wind sea waves. During the onset of the southwest monsoon (May), the sea direction is in the direction of swell propagation (northwest); however, during the southwest monsoon (June–August), a major part of the wind sea direction is from the southwest. The average occurrence of summer shamal swells is approximately 22% during the southwest monsoon period. An increase in wave height is observed during June and July at Ratnagiri due to the strong summer shamal event.

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Nearshore Currents along the Karnataka Coast, West Coast of India

The International Journal of Ocean and Climate Systems ◽

10.1260/1759-3131.3.1.71 ◽

2012 ◽

Vol 3 (1) ◽

pp. 71-84 ◽

Cited By ~ 7

Author(s):

V. Sanil Kumar ◽

G. Udhaba Dora ◽

C. Sajiv Philip ◽

P. Pednekar ◽

Jai Singh

Keyword(s):

West Coast ◽

Current Data ◽

Surface Currents ◽

The West ◽

Monsoon Period ◽

Near Surface ◽

West Coast Of India ◽

Average Value ◽

Alongshore Current ◽

Alongshore Wind

Measured current data at 7 locations and tide data at 3 locations during the pre-summer monsoon period along the west coast of India is used in the study. The surface currents during March showed a predominant northward trend and during April it was towards south. Estimated tidal currents were upto 25 cm s−1 with an average value of 8 cm s−1. Current tidal form number varied from 0.56 to 1 at different locations indicating currents are mixed. M2 and S2 tidal current constituents rotated clock wise at all location. Near surface, the alongshore current was 2.6 to 5.9% of the alongshore wind and near bottom it was 1.9 to 3.6% of the alongshore wind.

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