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 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 Marine Wind and Wave Height Trends at Different ERA-Interim Forecast Ranges

2015 ◽  
Vol 28 (2) ◽  
pp. 819-837 ◽  
Author(s):  
Ole Johan Aarnes ◽  
Saleh Abdalla ◽  
Jean-Raymond Bidlot ◽  
Øyvind Breivik
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
North Atlantic ◽  
Wave Model ◽  
Altimeter Data ◽  
The North ◽  
The Impact ◽  
Global Reanalysis ◽  
Made In

Abstract Trends in marine wind speed and significant wave height are investigated using the global reanalysis ERA-Interim over the period 1979–2012, based on monthly-mean and monthly-maximum data. Besides the traditional reanalysis, the authors include trends obtained at different forecast range, available up to 10 days ahead. Any model biases that are corrected differently over time are likely to introduce spurious trends of variable magnitude. However, at increased forecast range the model tends to relax, being less affected by assimilation. Still, there is a trade-off between removing the impact of data assimilation at longer forecast range and getting a lower level of uncertainty in the predictions at shorter forecast range. Because of the sheer amount of assimilations made in ERA-Interim, directly and indirectly affecting the data, it is difficult, if not impossible, to distinguish effects imposed by all updates. Here, special emphasis is put on the introduction of wave altimeter data in August 1991, the only type of data directly affecting the wave field. From this, it is shown that areas of higher model bias introduce quite different trends depending on forecast range, most apparent in the North Atlantic and eastern tropical Pacific. Results are compared with 23 in situ measurements, Envisat altimeter winds, and two stand-alone ECMWF operational wave model (EC-WAM) runs with and without wave altimeter assimilation. Here, the 48-h forecast is suggested to be a better candidate for trend estimates of wave height, mainly due to the step change imposed by altimeter observations. Even though wind speed seems less affected by undesirable step changes, the authors believe that the 24–48-h forecast more effectively filters out any unwanted effects.

scholarly journals Wave Observations from Central California: SeaSonde Systems andIn SituWave Buoys

2011 ◽  
Vol 2011 ◽  
pp. 1-18 ◽  
Author(s):  
Regan M. Long ◽  
Don Barrick ◽  
John L. Largier ◽  
Newell Garfield
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Strong Correlations ◽  
California Coast ◽  
Central California ◽  
Significant Wave ◽  
Wave Data ◽  
Reliable Source ◽  
Buoy Data

Wave data from five 12-13 MHz SeaSondes radars along the central California coast were analyzed to evaluate the utility of operational wave parameters, including significant wave height, period, and direction. Data from fourin situwave buoys served to verify SeaSonde data and independently corroborate wave variability. Hourly averaged measurements spanned distance is 150 km alongshore × 45 km offshore. Individual SeaSondes showed statistically insignificant variation over 27 km in range. Wave height inter-comparisons between regional buoys exhibit strong correlations, approximately 0.93, and RMS differences less than 50 cm over the region. SeaSonde-derived wave data were compared to nearby buoys over timescales from 15 to 26 months, and revealed wave height correlations and mean RMS difference of 53 cm. Results showed that height RMS differences are a percentage of significant wave height, rather than being constant independent of sea state. Period and directions compared favorably among radars, buoys, and the CDIP model. Results presented here suggest that SeaSondes are a reliable source of wave information. Supported by buoy data, they also reveal minimal spatial variation in significant wave height, period, and direction in coastal waters from ~45 km × ~150 km in this region of the central California coast. Small differences are explained by sheltering from coastal promontories, and cutoff boundaries in the case of the radars.

scholarly journals HOAPS and ERA-Interim precipitation over sea: Validation against shipboard in-situ measurements

2016 ◽  
Author(s):  
Karl Bumke ◽  
Gert König-Langlo ◽  
Julian Kinzel ◽  
Marc Schröder
Keyword(s):  
Reanalysis Data ◽  
Data Sets ◽  
Weather Forecasts ◽  
Rain Gauges ◽  
Medium Range ◽  
Temporal And Spatial ◽  
The Tropics ◽  
Along Track ◽  
Spatial Threshold

Abstract. The satellite derived HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data) and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data sets have been validated against in-situ precipitation measurements from ship rain gauges and optical disdrometers over the open-ocean by applying a statistical analysis for binary forecasts. For this purpose collocated pairs of data were merged within a certain temporal and spatial threshold into single events, according to the satellites' overpass, the observation and the forecast times. HOAPS detects the frequency of precipitation well, while ERA-Interim strongly overestimates it, especially in the tropics and subtropics. Although precipitation rates are difficult to compare because along-track point measurements are collocated with areal estimates and the numbers of available data are limited, we find that HOAPS underestimates precipitation rates, while ERA-Interim's Atlantic-wide average precipitation rate is close to measurements. However, regionally averaged over latitudinal belts, there are deviations between the observed mean precipitation rates and ERA-Interim. The most obvious ERA-Interim feature is an overestimation of precipitation in the area of the intertropical convergence zone and the southern sub-tropics over the Atlantic Ocean. For a limited number of snow measurements by optical disdrometers it can be concluded that both HOAPS and ERA-Interim are suitable to detect the occurrence of solid precipitation.

scholarly journals HOAPS and ERA-Interim precipitation over the sea: validation against shipboard in situ measurements

2016 ◽  
Vol 9 (5) ◽  
pp. 2409-2423 ◽  
Author(s):  
Karl Bumke ◽  
Gert König-Langlo ◽  
Julian Kinzel ◽  
Marc Schröder
Keyword(s):  
Reanalysis Data ◽  
Data Sets ◽  
Weather Forecasts ◽  
Rain Gauges ◽  
Medium Range ◽  
Temporal And Spatial ◽  
The Tropics ◽  
Along Track ◽  
Spatial Threshold

Abstract. The satellite-derived HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data) and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data sets have been validated against in situ precipitation measurements from ship rain gauges and optical disdrometers over the open ocean by applying a statistical analysis for binary estimates. For this purpose collocated pairs of data were merged within a certain temporal and spatial threshold into single events, according to the satellites' overpass, the observation and the ERA-Interim times. HOAPS detects the frequency of precipitation well, while ERA-Interim strongly overestimates it, especially in the tropics and subtropics. Although precipitation rates are difficult to compare because along-track point measurements are collocated with areal estimates and the number of available data are limited, we find that HOAPS underestimates precipitation rates, while ERA-Interim's Atlantic-wide average precipitation rate is close to measurements. However, when regionally averaged over latitudinal belts, deviations between the observed mean precipitation rates and ERA-Interim exist. The most obvious ERA-Interim feature is an overestimation of precipitation in the area of the intertropical convergence zone and the southern subtropics over the Atlantic Ocean. For a limited number of snow measurements by optical disdrometers, it can be concluded that both HOAPS and ERA-Interim are suitable for detecting the occurrence of solid precipitation.

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 Analysis of the NASA-POWER system for estimating reference evapotranspiration in the Comarca Lagunera, Mexico

2021 ◽  
Vol 13 (2) ◽  
pp. 201-226
Author(s):  
Sergio Iván Jiménez-Jiménez ◽  
◽  
Waldo Ojeda-Bustamante ◽  
Marco Antonio Inzunza-Ibarra ◽  
Mariana de Jesús Marcial-Pablo ◽  
...  
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Solar Radiation ◽  
Reference Evapotranspiration ◽  
Meteorological Data ◽  
Reanalysis Data ◽  
Measured Data ◽  
System Data ◽  
Data Source

Introduction: The FAO-56 Penman-Monteith (PM) is one of the most solid and commonly used methods for estimating reference evapotranspiration (ETo); however, it requires meteorological data that are not always available, so an alternative is the use of reanalysis data. Objective: To estimate the error that the NASA-POWER (NP) system data can generate in the ETo of the Comarca Lagunera, Mexico. Methodology: Daily and decadal average ETo were estimated in five different ways. In each case, a different method was used to estimate ETo (FAO-56 PM or Hargreaves and Samani [HS]) and a different meteorological data source (measured, NP data or combination of both). Results: NP data can be used to provide temperature, solar radiation and relative humidity variables, but not wind speed. The NP data overestimate the measured ETo, an RMSE of 1.15 and 0.89 mm∙d-1 was found for daily and decadal periods, respectively. Limitations of the study: A grid error analysis could not be carried out because the number of stations is limited. Originality: The use of reanalysis data to estimate ETo has not been analyzed locally. Conclusion: When measured data are not available, NP data and the HS equation can be used. When using the FAO-56 PM method and NP data, the in situ wind speed must be available.

Numerical Simulation of Typhoon Waves along the Offshore China Seas

2013 ◽  
Vol 303-306 ◽  
pp. 2736-2739
Author(s):  
Cong Ying Kong ◽  
Hong Sheng Cao ◽  
Xi Shan Pan ◽  
Wei Yi Zhang
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
Strong Dependence ◽  
Surface Wind ◽  
Space Distribution ◽  
Sea Surface Wind ◽  
Typhoon Wave ◽  
Typhoon Waves ◽  
Buoy Data ◽  
Surface Wind Field

The model of WAVEWATCHIII was applied to simulate two consecutive typhoons, number 1104”Haima” and number 1105”Meari”, and then the results of calculations were compared with the buoy data. The results show that under the influence of the typhoon, sea surface wind field and the significant wave height have similar symmetrical structure in the space distribution. In terms of time, with the development of typhoon, changes of the wind speed cause an invisible effect in wave height which explains that the wave height has very strong dependence on the wind speed. The analysis shows that the WAVEWATCHIII can simulate the characteristics of the typhoon wave.

scholarly journals Consistency of Temperature and Precipitation Extremes across Various Global Gridded In Situ and Reanalysis Datasets

2014 ◽  
Vol 27 (13) ◽  
pp. 5019-5035 ◽  
Author(s):  
Markus G. Donat ◽  
Jana Sillmann ◽  
Simon Wild ◽  
Lisa V. Alexander ◽  
Tanya Lippmann ◽  
...  
Keyword(s):  
Time Series ◽  
Extreme Precipitation ◽  
Climate Extremes ◽  
Reanalysis Data ◽  
Precipitation Extremes ◽  
Extreme Temperatures ◽  
Temperature And Precipitation ◽  
In Situ Observations ◽  
Temporal And Spatial

Changes in climate extremes are often monitored using global gridded datasets of climate extremes based on in situ observations or reanalysis data. This study assesses the consistency of temperature and precipitation extremes between these datasets. Both the temporal evolution and spatial patterns of annual extremes of daily values are compared across multiple global gridded datasets of in situ observations and reanalyses to make inferences on the robustness of the obtained results. While normalized time series generally compare well, the actual values of annual extremes of daily data differ systematically across the different datasets. This is partly related to different computational approaches when calculating the gridded fields of climate extremes. There is strong agreement between extreme temperatures in the different in situ–based datasets. Larger differences are found for temperature extremes from the reanalyses, particularly during the presatellite era, indicating that reanalyses are most consistent with purely observational-based analyses of changes in climate extremes for the three most recent decades. In terms of both temporal and spatial correlations, the ECMWF reanalyses tend to show greater agreement with the gridded in situ–based datasets than the NCEP reanalyses and Japanese 25-year Reanalysis Project (JRA-25). Extreme precipitation is characterized by higher temporal and spatial variability than extreme temperatures, and there is less agreement between different datasets than for temperature. However, reasonable agreement between the gridded observational precipitation datasets remains. Extreme precipitation patterns and time series from reanalyses show lower agreement but generally still correlate significantly.

scholarly journals Calibration and Cross Validation of a Global Wind and Wave Database of Altimeter, Radiometer, and Scatterometer Measurements

2017 ◽  
Vol 34 (6) ◽  
pp. 1285-1306 ◽  
Author(s):  
I. R. Young ◽  
E. Sanina ◽  
A. V. Babanin
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
Cross Validation ◽  
Extreme Values ◽  
Consistent Manner ◽  
Buoy Data

AbstractA combined satellite dataset consisting of nine altimeter, 12 radiometer, and two scatterometer missions of wind speed and wave height is calibrated in a consistent manner against NDBC data and independently validated against a separate buoy dataset. The data are investigated for stability as a function of time. Instances where there are discontinuities or drift in the data are identified and accounted for in the calibration. The performance of each of the instruments at extreme values is investigated using quantile–quantile comparisons with buoy data. The various instruments are cross validated at matchup locations where satellite ground tracks cross. The resulting calibrated and cross-validated dataset is believed to represent the largest global oceanographic dataset of its type, which includes multiple instrument types calibrated in a similar fashion.

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