scholarly journals Skill Assessment of an Atmosphere–Wave Regional Coupled Model over the East China Sea with a Focus on Typhoons

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 252 ◽  
Author(s):  
Delei Li ◽  
Joanna Staneva ◽  
Sebastian Grayek ◽  
Arno Behrens ◽  
Jianlong Feng ◽  
...  
Keyword(s):  
Wind Speed ◽  
East China Sea ◽  
Wave Height ◽  
Significant Wave Height ◽  
Reanalysis Data ◽  
The East China Sea ◽  
Typhoon Intensity ◽  
In Situ Observations ◽  
Simulated Wind

This study performed several sensitivity experiments to investigate the impact of atmosphere–wave coupling on the simulated wind and waves over the East China Sea (ECS) with a focus on typhoon events. These experiments include stand-alone regional atmosphere model (CCLM) simulations, stand-alone spectral wave model (WAM) simulations driven by the regional atmospheric model CCLM or ERA5 reanalysis, and two-way (CCLM-WAM) coupled simulations. We assessed the simulated wind speed and significant wave height against in situ observations and remote sensing data and focused on typhoon events in 2010. We analyzed the differences between the experiments in capturing the surface pressure, wind speed, and roughness length. Both ERA5 reanalysis data and our regional model simulations demonstrate high quality in capturing wind and wave conditions over the ECS. The results show that downscaled simulations tend to be closer to in situ observations than ERA5 reanalysis data in capturing wind variability and probability distribution, dominant wind and wave directions, strong typhoon intensity and related extreme significant wave height. In comparison with satellite observations, the CCLM-WAM simulation outperforms the CCLM in reducing wind bias. The coupled and uncoupled simulations are very similar in terms of other wind and wave statistics. Though there is much improvement in capturing typhoon intensity to ERA5, regional downscaled simulations still underestimate the wind intensity of tropical cyclones.

scholarly journals SARAL-AltiKa Wind and Significant Wave Height for Offshore Wind Energy Applications in the New England Region

2020 ◽  
Vol 13 (1) ◽  
pp. 57
Author(s):  
Xinba Li ◽  
Panagiotis Mitsopoulos ◽  
Yue Yin ◽  
Malaquias Peña
Keyword(s):  
Wind Speed ◽  
Wind Energy ◽  
New England ◽  
Wave Height ◽  
Significant Wave Height ◽  
Surface Wind ◽  
Offshore Wind ◽  
Significant Wave ◽  
In Situ Observations

The SARAL-AltiKa dataset was evaluated for refined offshore wind energy resources assessment and potential metocean monitoring capability in the Southern New England region. Surface wind speed and Significant Wave Height (Hs) products were assessed with corresponding variables from buoy observations for 2014–2019. To increase the sample size, this study analyzed and applied an approach to collect data around the reference buoys beyond the satellite footprint at the expense of a bias increment. The study corroborated the accuracy of the SARAL-AltiKa measurements for the offshore area of interest and added details for stations closer to the coast compared with past studies. A proportional bias with underestimation of high values of Hs was found in coastal sites. Wind speed estimates on the other hand appear to be less sensitive to the closeness to the coast. The empirical relationship between wind strength and Hs in the buoy observations is reproduced to a large extent by the AltiKa measurements in locations where land contamination is minimal. The histograms of surface wind and Hs are well described by the Weibull distribution and the shape and scale parameters closely resemble those of the histograms of the collocated in situ observations. We use these results to extrapolate the winds to a target domain with no in situ observations for wind energy resource estimation.

scholarly journals Evaluation of Sentinel-3A Wave Height Observations Near the Coast of Southwest England

2019 ◽  
Vol 11 (24) ◽  
pp. 2998 ◽  
Author(s):  
Francesco Nencioli ◽  
Graham D. Quartly
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Root Mean Square ◽  
Wave Height ◽  
Significant Wave Height ◽  
Mean Square ◽  
Significant Wave ◽  
In Situ Observations ◽  
Regression Slopes

Due to the smaller ground footprint and higher spatial resolution of the Synthetic Aperture Radar (SAR) mode, altimeter observations from the Sentinel-3 satellites are expected to be overall more accurate in coastal areas than conventional nadir altimetry. The performance of Sentinel-3A in the coastal region of southwest England was assessed by comparing SAR mode observations of significant wave height against those of Pseudo Low Resolution Mode (PLRM). Sentinel-3A observations were evaluated against in-situ observations from a network of 17 coastal wave buoys, which provided continuous time-series of hourly values of significant wave height, period and direction. As the buoys are evenly distributed along the coast of southwest England, they are representative of a broad range of morphological configurations and swell conditions against which to assess Sentinel-3 SAR observations. The analysis indicates that SAR observations outperform PLRM within 15 km from the coast. Within that region, regression slopes between SAR and buoy observations are close to the 1:1 relation, and the average root mean square error between the two is 0.46 ± 0.14 m. On the other hand, regression slopes for PLRM observations rapidly deviate from the 1:1 relation, while the average root mean square error increases to 0.84 ± 0.45 m. The analysis did not identify any dependence of the bias between SAR and in-situ observation on the swell period or direction. The validation is based on a synergistic approach which combines satellite and in-situ observations with innovative use of numerical wave model output to help inform the choice of comparison regions. Such an approach could be successfully applied in future studies to assess the performance of SAR observations over other combinations of coastal regions and altimeters.

scholarly journals Evaluation of in-situ wind speed and wave height measurements against reanalysis data for the Greek Seas

2017 ◽  
pp. 486 ◽  
Author(s):  
DAFNI SIFNIOTI ◽  
TAKVOR SOUKISSIAN ◽  
SERAFEIM POULOS ◽  
PANAGIOTIS NASTOS ◽  
MARIA HATZAKI
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
Reanalysis Data ◽  
Error Statistics ◽  
Evaluation Of Performance ◽  
Assimilation Process ◽  
Temporal And Spatial ◽  
Wave Hindcasting ◽  
Buoy Data

ERA-Interim, ECMWF’s reanalysis product, includes wave and atmospheric characteristics, with high temporal and spatial scale, providing more information on the marine state. Even though their assimilation process has been validated and verified in numerous studies, their performance in more local scales is still under examination. This research focuses on the evaluation of performance of ERA-Interim reanalysis datasets in the Greek Seas for wind and wave characteristics in comparison to POSEIDON buoy data. The results prove fair to good correlation for wave height (r = 0.67-0.94) and wind speed (r= 0.71-0.83) and different error statistics per sub-region. The upper 10% analysis shows an underestimate of 10-15% for wind speed and wave height from ERA-Interim in relation to the buoy measurements. The ERA-Interim and the buoy monthly means and standard deviations are also presented and discussed according to seasonal patterns. The results of the study are compared to other researches of wave hindcasting and wind reanalysis data for the Greek Seas and globally. It is shown that ERA-Interim products could be regarded as representative for the Greek Seas, although their application should be made with caution regarding the assessment of extreme conditions (i.e. given in analyses of upper percentiles) and especially at nearshore locations due to complex coastline configuration enhanced by the great number of islands.

scholarly journals Seasonal Exchanges of the Kuroshio and Shelf Waters and Their Impacts on the Shelf Currents of the East China Sea

2016 ◽  
Vol 46 (5) ◽  
pp. 1615-1632 ◽  
Author(s):  
Jia Wang ◽  
Lie Yauw Oey
Keyword(s):  
East China Sea ◽  
East China ◽  
Shelf Edge ◽  
The East China Sea ◽  
China Sea ◽  
Northeasterly Wind ◽  
In Situ Observations ◽  
Vorticity Production ◽  
The Kuroshio

AbstractPrevious in situ observations and modeling studies have indicated that, through mass and momentum exchanges across the shelf edge, the Kuroshio can significantly influence the shelf currents of the East China Sea (ECS). Here, instead of localized observations, this study uses 25 yr of drifter data, supported by satellite and other data to identify seasonal cross-shelf exchanges along the entire shelf edge. The authors show that Kuroshio meanders onshore from fall to winter and offshore from spring to summer, with the largest amplitude northeast of Taiwan. The influence is limited to the shelf edge when the Kuroshio meanders offshore in spring and summer. By contrast, strong onshelf intrusions and cross-shelf exchanges occur when the Kuroshio meanders onshore in fall and winter. Drifters intrude onshelf northeast of Taiwan and spread as far north as 30°N against the strong northeasterly wind. The forcing on the shelf is identified as a northward downsloping of the sea level that is steepest north of Taiwan at 25°–28°N, but which is 3 times weaker farther north. The vorticity budget computed from a numerical model indicates that intrusion during fall and winter is primarily a result of balance between onshelf advection of ambient potential vorticity and vorticity production by the along-isobath pressure gradient acting on the changing mass of water column across the continental slope.

scholarly journals Long-Term and Seasonal Trends in Global Wave Height Extremes Derived from ERA-5 Reanalysis Data

2020 ◽  
Vol 8 (12) ◽  
pp. 1015
Author(s):  
Alicia Takbash ◽  
Ian R. Young
Keyword(s):  
Southern Hemisphere ◽  
Wave Height ◽  
Significant Wave Height ◽  
Reanalysis Data ◽  
Extreme Value Analysis ◽  
Winter Storms ◽  
Value Analysis ◽  
Weather Forecasts ◽  
Significant Wave

A non-stationary extreme value analysis of 41 years (1979–2019) of global ERA5 (European Centre for Medium-Range Weather Forecasts Reanalysis) significant wave height data is undertaken to investigate trends in the values of 100-year significant wave height, Hs100. The analysis shows that there has been a statistically significant increase in the value of Hs100 over large regions of the Southern Hemisphere. There have also been smaller decreases in Hs100 in the Northern Hemisphere, although the related trends are generally not statistically significant. The increases in the Southern Hemisphere are a result of an increase in either the frequency or intensity of winter storms, particularly in the Southern Ocean.

scholarly journals Deep Atmospheric Response to the Spring Kuroshio over the East China Sea*

2011 ◽  
Vol 24 (18) ◽  
pp. 4959-4972 ◽  
Author(s):  
Haiming Xu ◽  
Mimi Xu ◽  
Shang-Ping Xie ◽  
Yuqing Wang
Keyword(s):  
Wind Speed ◽  
East China Sea ◽  
Surface Wind ◽  
Convective Precipitation ◽  
East China ◽  
Atmospheric Response ◽  
The East China Sea ◽  
Sst Front ◽  
China Sea ◽  
The Kuroshio

Abstract The atmospheric response to the spring Kuroshio Front over the East China Sea is investigated using a suite of high-resolution satellite data and a regional atmospheric model. The atmospheric response appears to extend beyond the marine atmospheric boundary layer, with frequent occurrence of cumulus convection. In spring, Quick Scatterometer (QuikSCAT) wind speed shows a clear effect of sea surface temperature (SST), with high (low) wind speed observed over the warm (cold) tongue. This in-phase relationship between SST and surface wind speed is indicative of SST influence on the atmosphere. Wind convergence is found on the warmer flank of the Kuroshio Front, accompanied by a narrow rainband. The analysis of satellite-borne radar measurements indicates that deep convection appears over the Kuroshio warm tongue in the spring season, with enhanced convective precipitation, frequent occurrence of cumulus convection, and increased precipitation (cloud) tops in altitude. These deep convective activities along the Kuroshio warm tongue are further supported by enhanced lightning flash rate observed by satellite and atmospheric heating estimated by a Japanese reanalysis. The Weather Research and Forecasting (WRF) model is used to investigate the precipitation response to the spring Kuroshio SST front over the East China Sea. Forced by observed SST [control (CTL)], the model well simulates a narrow band of precipitation, high wind speed, and surface wind convergence that closely follows the Kuroshio warm current, consistent with satellite observations. This narrow rainband completely disappears in the model when the SST front is removed by horizontally smoothed SST (SmSST). The results show that it is convective precipitation that is sensitive to the Kuroshio SST front. A case study for an eastward-moving extratropical cyclone indicates that convective precipitation increases its intensity and duration in the CTL run compared to the SmSST run. Local enhancement of upward sensible and latent heat fluxes and convective instability in the lower atmosphere are the key to anchoring the narrow band of convective precipitation that closely follows the Kuroshio.

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