Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis data
An assessment of extreme wave characteristics during the design of marine facilities not only helps to ensure their safety but also assess the economic aspects. In this study, return levels of significant wave height (<i>H</i><sub>s</sub>) for different periods are estima...
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2017-10-01
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doaj-f3d85a31ca174414a93841aeaa3517a32020-11-25T00:35:49ZengCopernicus PublicationsNatural Hazards and Earth System Sciences1561-86331684-99812017-10-01171763177810.5194/nhess-17-1763-2017Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis dataT. Muhammed Naseef0V. Sanil Kumar1Ocean Engineering Division, Council of Scientific and Industrial Research (CSIR)–National Institute of Oceanography, Dona Paula 403 004, IndiaOcean Engineering Division, Council of Scientific and Industrial Research (CSIR)–National Institute of Oceanography, Dona Paula 403 004, IndiaAn assessment of extreme wave characteristics during the design of marine facilities not only helps to ensure their safety but also assess the economic aspects. In this study, return levels of significant wave height (<i>H</i><sub>s</sub>) for different periods are estimated using the generalized extreme value distribution (GEV) and generalized Pareto distribution (GPD) based on the Waverider buoy data spanning 8 years and the ERA-Interim reanalysis data spanning 38 years. The analysis is carried out for wind-sea, swell and total <i>H</i><sub>s</sub> separately for buoy data. Seasonality of the prevailing wave climate is also considered in the analysis to provide return levels for short-term activities in the location. The study shows that the initial distribution method (IDM) underestimates return levels compared to GPD. The maximum return levels estimated by the GPD corresponding to 100 years are 5.10 m for the monsoon season (JJAS), 2.66 m for the pre-monsoon season (FMAM) and 4.28 m for the post-monsoon season (ONDJ). The intercomparison of return levels by block maxima (annual, seasonal and monthly maxima) and the <i>r</i>-largest method for GEV theory shows that the maximum return level for 100 years is 7.20 m in the <i>r</i>-largest series followed by monthly maxima (6.02 m) and annual maxima (AM) (5.66 m) series. The analysis is also carried out to understand the sensitivity of the number of observations for the GEV annual maxima estimates. It indicates that the variations in the standard deviation of the series caused by changes in the number of observations are positively correlated with the return level estimates. The 100-year return level results of <i>H</i><sub>s</sub> using the GEV method are comparable for short-term (2008 to 2016) buoy data (4.18 m) and long-term (1979 to 2016) ERA-Interim shallow data (4.39 m). The 6 h interval data tend to miss high values of <i>H</i><sub>s</sub>, and hence there is a significant difference in the 100-year return level <i>H</i><sub>s</sub> obtained using 6 h interval data compared to data at 0.5 h interval. The study shows that a single storm can cause a large difference in the 100-year <i>H</i><sub>s</sub> value.https://www.nat-hazards-earth-syst-sci.net/17/1763/2017/nhess-17-1763-2017.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
T. Muhammed Naseef V. Sanil Kumar |
spellingShingle |
T. Muhammed Naseef V. Sanil Kumar Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis data Natural Hazards and Earth System Sciences |
author_facet |
T. Muhammed Naseef V. Sanil Kumar |
author_sort |
T. Muhammed Naseef |
title |
Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis data |
title_short |
Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis data |
title_full |
Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis data |
title_fullStr |
Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis data |
title_full_unstemmed |
Variations in return value estimate of ocean surface waves – a study based on measured buoy data and ERA-Interim reanalysis data |
title_sort |
variations in return value estimate of ocean surface waves – a study based on measured buoy data and era-interim reanalysis data |
publisher |
Copernicus Publications |
series |
Natural Hazards and Earth System Sciences |
issn |
1561-8633 1684-9981 |
publishDate |
2017-10-01 |
description |
An assessment
of extreme wave characteristics during the design of marine facilities not
only helps to ensure their safety but also assess the economic aspects. In
this study, return levels of significant wave height (<i>H</i><sub>s</sub>) for different
periods are estimated using the generalized extreme value distribution (GEV)
and generalized Pareto distribution (GPD) based on the Waverider buoy data
spanning 8 years and the ERA-Interim reanalysis data spanning 38 years. The
analysis is carried out for wind-sea, swell and total <i>H</i><sub>s</sub> separately for
buoy data. Seasonality of the prevailing wave climate is also considered in
the analysis to provide return levels for short-term activities in the
location. The study shows that the initial distribution method (IDM)
underestimates return levels compared to GPD. The maximum return levels
estimated by the GPD corresponding to 100 years are 5.10 m for the monsoon
season (JJAS), 2.66 m for the pre-monsoon season (FMAM) and 4.28 m for the
post-monsoon season (ONDJ). The intercomparison of return levels by block
maxima (annual, seasonal and monthly maxima) and the <i>r</i>-largest method for GEV
theory shows that the maximum return level for 100 years
is 7.20 m in the <i>r</i>-largest series followed by monthly maxima (6.02 m) and
annual maxima (AM) (5.66 m) series. The analysis is also carried out to
understand the sensitivity of the number of observations for the GEV annual
maxima estimates. It indicates that the variations in the standard deviation
of the series caused by changes in the number of observations are positively
correlated with the return level estimates. The 100-year return level results of <i>H</i><sub>s</sub>
using the GEV method are comparable for short-term (2008 to 2016)
buoy data (4.18 m) and long-term (1979 to 2016) ERA-Interim shallow data
(4.39 m). The 6 h interval data tend to miss high values of <i>H</i><sub>s</sub>, and hence
there is a significant difference in the 100-year return level <i>H</i><sub>s</sub> obtained
using 6 h interval data compared to data at 0.5 h interval. The study shows
that a single storm can cause a large difference in the 100-year <i>H</i><sub>s</sub> value. |
url |
https://www.nat-hazards-earth-syst-sci.net/17/1763/2017/nhess-17-1763-2017.pdf |
work_keys_str_mv |
AT tmuhammednaseef variationsinreturnvalueestimateofoceansurfacewavesastudybasedonmeasuredbuoydataanderainterimreanalysisdata AT vsanilkumar variationsinreturnvalueestimateofoceansurfacewavesastudybasedonmeasuredbuoydataanderainterimreanalysisdata |
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