An analytical algorithm with a wave age factor for altimeter wind speed retrieval

Cheng, Yongcun; Xu, Qing; Liu, Yuguang; Lin, Hui; Xiu, Peng; Yin, Xiaobin; Zong, Hong-Shi; Rong, Zengrui

doi:10.1080/01431160801908111

Cited by 13 publications

(7 citation statements)

References 19 publications

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“…The influence of sea state on altimeter measurements has already been established and well documented [1]- [3]. Moreover, wave parameters such as significant wave height (H s ) and wave age are often adopted 0196-2892/$31.00 © 2012 IEEE to characterize sea state conditions, to improve the relationship (e.g., [4]- [6]). Hwang et al [7] conducted a statistical comparison of wind speed, wave height, and wave period derived from satellite altimeters and ocean buoys in the Gulf of Mexico region and concluded that the wind speed accuracy is significantly improved when local incidence angle modification by surface tilting is taken into account.…”

Section: Introductionmentioning

confidence: 99%

Relationships Between Ku-Band Radar Backscatter and Integrated Wind and Wave Parameters at Low Incidence Angles

Chu

Karaev

2012

IEEE Trans. Geosci. Remote Sensing

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By using ten years of collocated Precipitation Radar and buoy data, the relationships between Ku-band normalized radar cross section (σ • ) and integrated wind and wave parameters (e.g., significant wave height, wave period, wave steepness, and wave age) at low incidence angles are analyzed for different sea states using correlation and dependence analysis. The results show that the relationships are significantly different for different sea states. Second, the potential for inverting these parameters directly from a single σ • is investigated. The results reveal that the retrieval of wind speed above 10 m (U 10 ) is most suitable for a nonpure-swell sea and that the performance of significant wave height (H s ) retrieval decreases with the ratio of swell to wind waves. For wave period and wavelength, a feasible inversion can only be performed for a wind-wave-dominated sea. Wave steepness (δ a ) is strongly correlated with σ • in all sea states and can even be higher than that for U 10 in pure-swell seas. It is suggested from the present data set that real wave age (β) may be retrieved from a swell-dominated sea and, therefore, has a low-value cutoff. Furthermore, the extent to which U 10 retrieval depends on sea state is examined by calculating the correlation coefficient between σ • residuals and various standard wave parameters and, then, by determining the partial correlation coefficient between σ • and each wave parameter controlled by U 10 . Both results indicate that wind direction is better taken into account above 13.5 • . Moreover, an auxiliary parameter related to wave slope, such as wave steepness, would help to improve retrieval performance. Significant wave height data are of secondary use, but an implementation with real wave age information might not significantly improve wind speed retrieval. To improve the performance of H s and wave period retrieval, auxiliary information, such as wind speed, wave steepness, or wave age, is needed. Finally, multivariable empirical models are proposed.Index Terms-Integral wave parameter, low-incidence-angle remote sensing, radar cross section, radar signal analysis.

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Section: Introductionmentioning

confidence: 99%

Relationships Between Ku-Band Radar Backscatter and Integrated Wind and Wave Parameters at Low Incidence Angles

Chu

Karaev

2012

IEEE Trans. Geosci. Remote Sensing

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“…Numerous past studies suggested sea-state impacts on altimeter wind estimations and parameterized this impact in terms of significant wave height [1][2][3][4] or wave age [10]. For PR, as discussed in our introduction, pervious investigations also revealed that long-wave tilting effects are significant [6] and measurement of the sea surface slope component contributing to the tilting may be needed to achieve the maximum potential of the radar wind sensing at low incidence angles.…”

Section: Two-parameter Model Functionsmentioning

confidence: 91%

A new algorithm for wind speed at low incidence angles using TRMM Precipitation Radar data

Chu

Chen

2010

2010 IEEE International Geoscience and Remote Sensing Symposium

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Large datasets from crossovers of Precipitation Radar (PR) and buoy observations clearly demonstrate that ocean PR backscatter correlates with both the near-surface wind speed and the sea surface wave slope. Multi-incidence angles PR data are used to retrieve surface wave slope parameter and normalized nadir backscatter. After that, an empirical wind speed model was developed based on those two parameters that attenuates the surface tilting effect. The inversion is defined using a multilayer perceptron neural network with radar-derived backscatter and surface wave slope parameter as inputs. Results show the root mean square errs between retrieved wind speeds and in situ buoy observations is 1.36m/s, bias is nearly zero, revealing good agreements in wind speed estimations.

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“…According to the Stokes' second-order theory, the horizontal and vertical components are functions of wave period, height, and steepness [39]. Wind wave steepness is a function of wave age and young age wind waves are much steeper, as described in [40], and a wind-wave spectrum model described in [41] shows how wave age affects the spectral peak and energy distribution, which is also used to retrieve the wind speed [42]. Consequently, if wind waves show up in an amplitude spectrum, the wave age must be taken into consideration to improve the accuracy of the retrieval of wave period and height.…”

Section: Discussionmentioning

confidence: 99%

Ocean Wave Measurement Using Short-Range K-Band Narrow Beam Continuous Wave Radar

et al. 2018

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Abstract:We describe a technique to measure ocean wave period, height and direction. The technique is based on the characteristics of transmission and backscattering of short-range K-band narrow beam continuous wave radar at the sea surface. The short-range K-band radar transmits and receives continuous signals close to the sea surface at a low-grazing angle. By sensing the motions of a dominant facet at the sea surface that strongly scatters signals back and is located directly in front of the radar, the wave orbital velocity can be measured from the Doppler shift of the received radar signal. The period, height and direction of ocean wave are determined from the relationships among wave orbital velocity, ocean wave characteristics and the Doppler shift. Numerical simulations were performed to validate that the dominant facet exists and ocean waves are measured by sensing its motion. Validation experiments were conducted in a wave tank to verify the feasibility of the proposed ocean wave measurement method. The results of simulations and experiments demonstrate the effectiveness of the short-range K-band narrow beam continuous wave radar for the measurement of ocean waves.

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An analytical algorithm with a wave age factor for altimeter wind speed retrieval

Cited by 13 publications

References 19 publications

Relationships Between Ku-Band Radar Backscatter and Integrated Wind and Wave Parameters at Low Incidence Angles

Relationships Between Ku-Band Radar Backscatter and Integrated Wind and Wave Parameters at Low Incidence Angles

A new algorithm for wind speed at low incidence angles using TRMM Precipitation Radar data

Ocean Wave Measurement Using Short-Range K-Band Narrow Beam Continuous Wave Radar

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