Changes in nearshore waves during the active sea/land breeze period off Vengurla, central west coast of India

George

2016

Ann. Geophys.

Abstract. We assess the influence of monsoon variability on the surface waves using measured wave data covering 7 years and reanalysis data from 1979 to 2015 during the Indian summer monsoon (JJAS) in the eastern Arabian Sea. The interannual comparison shows that the percentage of higher wave heights ( > 2.5 m) is higher (∼ 26%) in 2014 than in other years due to the higher monsoon wind speed (average speed ∼ 7.3 m s −1 ) in 2014. Due to the delayed monsoon, monthly average significant wave height (H m0 ) of June was lowest (∼ 1.5 m) in 2009. The spectral peak shifted to lower frequencies in September due to the reduction of wind seas as a result of decrease in monsoon intensity. The study shows high positive correlation (r ∼ 0.84) between average lowlevel jet (LLJ) for the block 0-15 • N, 50-75 • E and H m0 of eastern Arabian Sea in all the months except in August (r ∼ 0.66). The time series data on wave height shows oscillations with periods 5 to 20 days. Wavelet coherence analysis indicates that the LLJ and H m0 are in-phase related (phase angle 0 • ) almost all the time and LLJ leads H m0 . The monsoon seasonal anomaly of H m0 is found to have a negative relationship with the Oceanic Niño Index indicating that the monsoon average H m0 is relatively low during the strong El Niño years.

Section: Study Areamentioning

confidence: 98%

Influence of Indian summer monsoon variability on the surface waves in the coastal regions of eastern Arabian Sea

George

2016

Ann. Geophys.

“…So, the observed deviation from the recommended value (−3) is relatively weak. Amrutha et al (2016) observed that for frequencies from 0.229 to 0.58 Hz at 15 m water depth in eastern AS during January-May, the highfrequency tail has f −2.5 and at 5 m water depth, frequencies from 0.315 to 0.55 Hz has the high-frequency tail f −3 . The study shows that the values observed in the present study are like the ones observed in the eastern AS.…”

Section: High-frequency Tail Of Wave Spectrummentioning

confidence: 99%

Features of locally and remotely generated surface gravity waves in the inner‐shelf region of northwestern Bay of Bengal

Nair

Intl Journal of Climatology

Amrutha

et al. 2018

Self Cite

In this article, we studied the characteristics of locally and remotely generated wind waves in the inner‐shelf region of northwestern Bay of Bengal (BoB) based on the measured wave data. Two well‐differentiated wave systems, one young sea from the east‐southeast and another more developed swell from the south lead to bimodality in the wave spectrum. Wind‐sea predominance is not observed in the monthly average wave spectrum and in all the months swells dominated indicating a swell‐driven wave regime. During the monsoon (JJAS), the wave climate is dominated by long‐period swell from the south‐southeast and the short fetch during the northeast monsoon (ONDJ) leads to weaker easterly swells, while the effects of the sea/land breeze influence on the wave generation are more relevant during this season. During November–April, diurnal variation of 0.15 m in significant wave height (SWH) is observed. The study based on seasonally averaged ERA‐Interim reanalysis data reveals a weak connection between the waves in the northwestern BoB and the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events. The waves are influenced by ENSO events during June–September and by IOD events during October–January, which consequently caused inter‐annual variations in monthly average SWH. The present study, however, did not show a significant inter‐annual variability in annual mean SWH during 1979–2015.

“…It is surrounded by a semicircular range of hills and is exposed to open ocean waves from northwest to south. The nearest landmass is ∼1500 km in the northwest, ∼2000 km in the west, ∼4000 km southwest and ∼9000 km in the south [30]. The Vengurla coast is characterized by a tropical climate, and the annual precipitation is~3100 mm [31].…”

Section: Study Areamentioning

confidence: 99%

Nearshore Waves and Littoral Drift Along a Micro-Tidal Wave-Dominated Coast Having Comparable Wind-Sea and Swell Energy

George

Gowthaman

et al. 2020

JMSE

The nearshore wave characteristics and variations in littoral drift (longshore sediment transport; LST) are estimated based on different approaches for four years along the Vengurla coast, with comparable wind-sea and swell energy assessed. The waverider buoy-measured data at 15 m water depth is utilized as the input wave parameters along with the reanalysis model data, and the numerical wave model Delft-3D is used for estimating the nearshore wave parameters. The relative contribution of wind-seas and swells on LST rates are specifically examined. The clear prevalence of west-southwest waves implies the prevalence of south to north longshore sediment transport with net transport varying from 0.19–0.37 × 105 m3/yr. LST is strongly dependent on the breaker angle and a small change in the wave direction substantially alters the LST, and hence reanalysis/model data with coarse resolutions produce large errors (~38%) in the LST estimate. The annual gross LST rate based on integral wave parameters is only 58% considering the wind-seas and swells separately, since the wind-sea energy is comparable to swell energy, and the direction of these two systems differs significantly.