Characteristics of high monsoon wind-waves observed at multiple stations in the eastern Arabian Sea

Amrutha, M. M.; Kumar, V. Sanil

doi:10.5194/os-2017-84

Cited by 9 publications

(3 citation statements)

References 15 publications

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“…The H max / H s ratio in the study area varies from 1.46 to 2.3 with an average value of 1.87 during 1979–2017. Amrutha and Sanil Kumar () observed that in the coastal waters of the eastern Arabian Sea, the H max / H s ratio is 1.50–1.62 times the H s for different locations.…”

Section: Resultsmentioning

confidence: 99%

Climatology and trends of the Indian Ocean surface waves based on 39‐year long ERA5 reanalysis data

Naseef

Kumar

2019

Intl Journal of Climatology

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In this study, the wind and the surface waves in the Indian Ocean (IO) during 1979–2017 are studied based on the ECMWF ERA5 Reanalysis data. Long‐term statistical analysis of extreme waves is carried out based on Generalized Extreme Value distribution using annual maxima and the spatial distribution of return levels for 50 and 100 years are studied. In general, the ERA5 significant wave height (Hs) and maximum wave height (Hmax) show a good agreement with measured buoy data in the coastal (bias ~0.29 m) and deep waters (bias ~0.18 m). During the tropical cyclone, underestimation of Hs and Hmax in the ERA5 data compared to buoy data is 2.7 and 1.4%, but in general the bias is large (~0.69 m). Swell domination is observed in larger regions of the IO, whereas wind‐seas are comparable to swells in the Southern Ocean. The meridional wind speed largely influences the spatial pattern of Hs in the North IO. The stronger winds over the Southern Ocean play a major role in generating higher waves at higher latitudes. Maximum value of the 100‐year return level for Hs in IO is 17.8 m, whereas highest value of the Hs is 16.7 m and Hmax is 32.0 m. Severe wave events are common at 50°–60°S and only during 25% of the time in a year, Hmax is less than 5 m in this region. Ratio of the Hmax to Hs varies from 1.46 to 2.3 with a mean value of 1.87. The 100‐year return value of Hs changed by −4 to 5 m, when the length of the dataset is decreased from 39 years (1979–2017) to recent 20 years. On an average, from 1979 to 2017, the annual average Hmax increased by 0.73 cm/year. In major areas of the IO, a clear decrease of the Hs is observed during 1991–2017, whereas during 1979–2017, an increase in Hs is found.

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Section: Resultsmentioning

confidence: 99%

Climatology and trends of the Indian Ocean surface waves based on 39‐year long ERA5 reanalysis data

Naseef

Kumar

2019

Intl Journal of Climatology

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“…During JJA, the AS is dominated by mixed sea state i. e, a combination of strong monsoon winds forced wind sea and swell 22 , 29 and peak wave period above 15 s is rarely seen in this period indicating non-dominance of SIO swells. A recent study shows that the SIO swell propagation is more towards BOB during JJA 41 .…”

Section: Resultsmentioning

confidence: 99%

The influence of boreal summer intra-seasonal oscillations on Indo-western Pacific Ocean surface waves

Srinivas

Remya

Malavika

et al. 2020

Sci Rep

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The present study examines the influence of Boreal Summer Intra-Seasonal Oscillation (BSISO) on Tropical Indian Ocean surface waves using the latest version of ECMWF reanalysis (ERA5) during summer monsoon months June through August (JJA). BSISO is a distinct mode of ISO during JJA having a northward and eastward movement from the equatorial Indian Ocean to the western Pacific Ocean. Composite analysis of anomalies of significant wave heights (SWH), wind sea, swell, and mean wave period for 8 phases of BSISO has been carried out to understand its influence. SWH anomalies in response to BSISO’s are phase-dependent. Negative SWH anomalies are noticed with strong northward and weak eastward propagation during the phases 1–3 in response to the easterly wind anomalies over the north Indian Ocean (NIO). During phases 5–7, high positive SWH anomalies (~ 0.5 m) in response to the westerly wind anomalies with northward and weak eastward propagation over NIO. Phases 4 and 8 behave like transition phases. In addition, enhanced (suppressed) SWH anomalies (~ 0.5 m) are seen during the active (break) spells of BSISO over NIO. Over the southern tip of India, negative (positive) SWH anomalies prevail during the active (break) conditions. This study clearly suggests that the wave forecast advisories during intra-seasonal time scales would be more useful for offshore and coastal activities during the summer monsoon.

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“…In the SW monsoon season, the enhanced south‐westerlies in the Indian Ocean strengthen the generated swells. The high waves (SWH ~3 to 5.5 m) in the eastern AS during the SW monsoon are because of the strong cross‐equatorial winds of the Findlater Jet (Findlater, 1969), which produces high waves of 4–6 m in the western AS and propagate to the eastern AS (Amrutha and Sanil Kumar, ). In the study area, SW monsoon wave heights are larger and elevated above 1.5 m during 38.4% of the time.…”

Section: Discussionmentioning

confidence: 99%

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

Nair

Kumar

Amrutha

et al. 2018

Intl Journal of Climatology

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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.

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Characteristics of high monsoon wind-waves observed at multiple stations in the eastern Arabian Sea

Cited by 9 publications

References 15 publications

Climatology and trends of the Indian Ocean surface waves based on 39‐year long ERA5 reanalysis data

Climatology and trends of the Indian Ocean surface waves based on 39‐year long ERA5 reanalysis data

The influence of boreal summer intra-seasonal oscillations on Indo-western Pacific Ocean surface waves

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

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