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Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows)

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A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Ocean Remote Sensing".

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 19221

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Special Issue Editors

Dr. Vladimir A. Dulov

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Guest Editor

Marine Hydrophysical Institute, Russian Academy of Sciences, 2 Kapitanskaya, 299011 Sevastopol, Russia
Interests: experimental and satellite oceanography; remote sensing; wind waves and wave breaking; small-scale wind waves; wave-wave and wave-current interactions; image and video processing

Dr. Bertrand Chapron

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Guest Editor

French Research Institute for Exploitation of the Sea (IFREMER), 29280 Plouzané, France
Interests: oceanographic techniques; synthetic aperture radar; wind; ocean waves; remote sensing by radar; radar imaging; atmospheric techniques; neural nets; geophysical image processing; learning (artificial intelligence); radiometry; sea ice; atmospheric humidity; data assimilation; radar polarimetry;r emote sensing; spaceborne radar; Kalman filters; calibration; ocean temperature; oceanographic equipment; oceanographic regions; altimeters; clouds; geophysics computing
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Prof. Dr. Vladimir N. Kudryavtsev

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Guest Editor

Satellite Oceanography Laboratory, Russian State Hydrometeorological University, 195196 St. Petersburg, Russia
Interests: experimental and satellite oceanography; remote sensing; wind waves and wave breaking; small-scale wind waves; wave-wave and wave-current interactions; image and video processing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Tropical cyclones (TCs), including Mediterranean hurricanes, are well-known natural disasters that pose enormous threats to coastal activities and human living, generating abnormal waves, strong winds, rainfall, storm surges, and flooding. Polar lows (PLs), less-intense analogs of TCs, also pose potential threats to developing coastal activities and shipping in the Arctic, as well as impacting the growing ice-free Arctic areas. The TC-generated surface currents and waves have significant impacts on the ocean's upper layer, being the cause of baroclinic movements, vertical mixing, and thermocline erosion. The air–sea interaction processes and surface fluxes are also strongly affected by intense wave breaking and spray under extreme weather conditions.

Any significant progress in the modeling of TC/PL dynamics and waves and relating the air–sea interaction process under TC/PL require extensive in situ and remote-sensing observations. The latter is the most effective way to provide data on atmospheric and ocean parameters in extreme conditions using and combining microwave and optical measurements from different instruments and platforms including satellites and aircraft.

This open access Special Issue invites high-quality and innovative scientific papers focusing on the remote sensing of surface waves, ocean surfaces, and air–sea interaction processes under TC/PL. The potential topics include but are not limited to:

Methods and algorithms for measurements and retrieval of the governing surface parameters, wind velocity, surface fluxes, wind waves and wave breaking, surface currents, SSH-SST and SSS anomalies, and upper ocean color changes under TC/PL using satellite microwave and optical data. The combined use of passive and radar data as well as data of new satellite missions, e.g., CFOSAT, is welcomed.
Specific features of wind waves and swell fields and their dependence on the wind speed, radius and translation velocity of TC/PL derived from the synergetic analysis of satellite data and modelling.
Short wind waves, wave breaking and spray under TC/PL; physics, modeling, laboratory experiments, and implementation in radar scattering and microwave emission models.
The combined analysis of TC/PL-induced SSH-SST-SSS anomalies, upper ocean color changes (wakes), and surface currents using satellite and in situ observations and modeling.

Dr. Vladimir A. Dulov
Dr. Bertrand Chapron
Prof. Dr. Vladimir N. Kudryavtsev
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Tropical cyclones
Mediterranean hurricanes
Polar lows
Remote sensing of tropical cyclones and polar lows
Remote sensing of wind-driven and swell wave fields
Remote sensing of sea-surface phenomena under extreme weather conditions
Wind-driven and swell wave fields generated by tropical cyclones
Air–sea interactions under extreme weather conditions
Submesoscale air–sea interactions under tropical cyclones
SSH-SST-SSS anomalies
Upper ocean color changes

Published Papers (11 papers)

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Research

17 pages, 5284 KiB

Open AccessArticle

Coastal Flood Mapping with Two Approaches Based on Observations at Furadouro, Northern Portugal

by Jose E. Carneiro-Barros, Theocharis A. Plomaritis, Tiago Fazeres-Ferradosa, Paulo Rosa-Santos and Francisco Taveira-Pinto

Remote Sens. 2023, 15(21), 5215; https://doi.org/10.3390/rs15215215 - 02 Nov 2023

Cited by 1 | Viewed by 1096

Abstract

This study assesses coastal flooding extension mapping based on two innovative approaches. The first is based on the coupling of two robust numerical models (SWASH and LISFLOOD); in this case, discharges were extracted from the wave overtopping results from SWASH 1D and set as boundary conditions for LISFLOOD on the crest of an existing seawall where overtopping typically occurs. The second, hereby called the ‘Tilted Bathtub Approach’ (TBTA), is based on wave run-up levels and buffering the affected area of a prior flooding event, adjusting it for expected sea states according to different return periods. The proposed approaches are applied to a case study on the Northern Portuguese coast, at Furadouro beach, in the municipality of Ovar, which has been facing multiple flooding episodes throughout recent years, including a dramatic storm in February 2014. This event was used as validation for the proposed methods. A 30-year-long hourly local wave climate time series was used both to perform an extreme value analysis in order to obtain expected sea states according to different return periods and also for performing a sensitivity test for established empirical formulas to estimate wave run-up in this particular case. Results indicate both approaches are valuable: they yield coherent flood extension predictions that align well with the real inundated area from the 2014 storm. The convergence of these findings underscores the potential for these methods in future coastal flood risk assessment, planning, and understanding of coastal responses under extreme weather conditions. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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17 pages, 4272 KiB

Open AccessArticle

A CatBoost-Based Model for the Intensity Detection of Tropical Cyclones over the Western North Pacific Based on Satellite Cloud Images

by Wei Zhong, Deyuan Zhang, Yuan Sun and Qian Wang

Remote Sens. 2023, 15(14), 3510; https://doi.org/10.3390/rs15143510 - 12 Jul 2023

Viewed by 866

Abstract

A CatBoost-based intelligent tropical cyclone (TC) intensity-detecting model was built to quantify the intensity of TCs over the Western North Pacific (WNP) with the cloud-top brightness temperature (CTBT) data of Fengyun-2F (FY-2F) and Fengyun-2G (FY-2G) and the best-track data of the China Meteorological Administration (CMA-BST) in recent years (2015–2018). The CatBoost-based model was featured with the greedy strategy of combination, the ordering principle in optimizing the possible gradient bias and prediction shift problems, and the oblivious tree in fast scoring. Compared with the previous studies based on the pure convolutional neural network (CNN) models, the CatBoost-based model exhibited better skills in detecting the TC intensity with the root mean square error (RMSE) of 3.74 m s⁻¹. In addition to the three mentioned model features, there are also two reasons for the model’s design. On one hand, the CatBoost-based model used the method of introducing prior physical factors (e.g., the structure and shape of the cloud, deep convections, and background fields) into its training process. On the other hand, the CatBoost-based model expanded the dataset size from 2342 to 13,471 samples through hourly interpolations of the original dataset. Furthermore, this paper investigated the errors of this model in detecting the different categories of TC intensity. The results showed that the deep learning-based TC intensity-detecting model proposed in this paper has systematic biases, namely, the overestimation (underestimation) of intensities in TCs which were weaker (stronger) than at the typhoon level, and the errors of the model in detecting weaker (stronger) TCs were smaller (larger). This implies that more factors than the CTBT should be included to further reduce the errors in detecting strong TCs. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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21 pages, 23266 KiB

Open AccessArticle

On Surface Waves Generated by Extra-Tropical Cyclones—Part II: Simulations

by Vahid Cheshm Siyahi, Vladimir Kudryavtsev, Maria Yurovskaya, Fabrice Collard and Bertrand Chapron

Remote Sens. 2023, 15(9), 2377; https://doi.org/10.3390/rs15092377 - 30 Apr 2023

Viewed by 1345

Abstract

In the previous companion study, satellite data were used to describe peculiar characteristics of ocean surface wave fields, generated by two extra-tropical cyclones (ETCs) rapidly propagating in the North Atlantic. Based on a 2D parametric wave model, further details are now provided to analyse and interpret the spatio-temporal evolution of very intense ETC-generated waves. Significant wave height and wavelength values are shown to reach extreme values, 18 m and 500 m, respectively. Resulting energetic swell systems waves then radiate in the whole eastern part of the North Atlantic, and more particularly in the Norwegian sea region. Moving to higher latitudes, wind forcing characteristics of ETCs evolve, with the shape of the wind field changing from quasi-cyclonic to “air jets/Icelandic lows”. In this paper, the resulting swell generation and propagation, after the deformation of an individual ETC, were studied, as well. Confirmed with comparisons with multi-satellite observations, the application of the parametric-2D wave-ray model was demonstrated to provide robust and highly detailed information on wave generation under very complex wind regime changes. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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18 pages, 6391 KiB

Open AccessArticle

Landsat-8 Observations of Foam Coverage under Fetch-Limited Wave Development

by Vladimir A. Dulov, Ekaterina V. Skiba and Arseny A. Kubryakov

Remote Sens. 2023, 15(9), 2222; https://doi.org/10.3390/rs15092222 - 22 Apr 2023

Viewed by 1001

Abstract

In this paper, we aimed to clarify the problem of foam coverage dependence on wave fetch, which is of interest in satellite microwave radiometry, but for which controversial results were reported previously. The classical approach to investigating developing waves was applied. That is, the waves are considered as coming from the coast under approximately constant wind velocity. The study includes two scenes of intensive katabatic winds in the Gulf of Lion and the Gulf of Tehuantepec. We used two Bands of Landsat OLI images to extract the wave spectral peak frequency and the sea fraction covered by foam simultaneously along the wave fetch. The distributions of the spectral peak frequency along the fetch obeying the classical wave growth law clearly showed that we observed the developing waves. Along the fetch, the sea surface covered with foam grows about three times with the power law. This development of foam coverage occurred at the range of dimensionless fetches from 50 up to 7000 if the fetch is scaled using wind velocity and gravity acceleration. A simple model of the foam coverage growth with wave fetch is suggested. We modeled wave energy dissipation rate using the JONSWAP wave spectrum for developing seas. The model explains the observations at the quantitative level. Reported results can be applied to investigations of tropical cyclones using satellite microwave radiometry. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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20 pages, 8340 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Spatial and Temporal Criteria for Altimeter Collocation of Significant Wave Height and Wind Speed Data in Deep Waters

by Ricardo M. Campos

Remote Sens. 2023, 15(8), 2203; https://doi.org/10.3390/rs15082203 - 21 Apr 2023

Cited by 1 | Viewed by 1396

Abstract

This paper investigates the spatial and temporal variability of significant wave height (Hs) and wind speed (U10) using altimeter data from the Australian Ocean Data Network (AODN) and buoy data from the National Data Buoy Center (NDBC). The main goal is to evaluate spatial and temporal criteria for collocating altimeter data to fixed-point positions and to provide practical guidance on altimeter collocation in deep waters. The results show that a temporal criterion of 30 min and a spatial criterion between 25 km and 50 km produce the best results for altimeter collocation, in close agreement with buoy data. Applying a 25 km criterion leads to slightly better error metrics but at the cost of fewer matchups, whereas using 50 km augments the resulting collocated dataset while keeping the differences to buoy measurements very low. Furthermore, the study demonstrates that using the single closest altimeter record to the buoy position leads to worse results compared to the collocation method based on temporal and spatial averaging. The final validation of altimeter data against buoy observations shows an RMSD of 0.21 m, scatter index of 0.09, and correlation coefficient of 0.98 for Hs, confirming the optimal choice of temporal and spatial criteria employed and the high quality of the calibrated AODN altimeter dataset. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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19 pages, 28723 KiB

Open AccessArticle

Influence of Multiple Interactions of Three Typhoons and a Mid-Latitude Cloud Band-Associated Trough in the North West Pacific upon Severe Tropical Storm Linfa

by Soo-Min Choi and Hyo Choi

Remote Sens. 2023, 15(8), 2170; https://doi.org/10.3390/rs15082170 - 20 Apr 2023

Viewed by 1157

Abstract

Multiple interactions of three typhoons and a mid-latitude cloud band-associated with a trough (MLCT) were investigated from 1 July to 10 July 2015, using the Korea Communication, Ocean, and Meteorological Satellite (COMS) satellite images and two kinds of meteorological models, such as UM-KMA (U.K.) and WRF-3.6 (U.S.A.), to generate the horizontal structure of wind and relative humidity, streamline, and moisture flux. As severe tropical storm (STS) Linfa moved toward the warmer area with a sea surface temperature (SST) of 31 °C in the northern South China Sea, it obtained not only more moisture by thermal convection of water vapor from the sea surface toward the lower atmosphere but also more momentum by its multiple interactions with both the MLCT and Typhoon (TY) Chan-Hom. Through their mutual interactions, mutual feedback of moisture and momentum fluxes could accelerate the formation of clouds in their systems and an asymmetric structure of their circulations. After Linfa weakened due to the increased friction of the shallower sea bottom close to the Chinese coast and its disconnection from the MLCT, later it became re-intensified with the increased wind speeds by a stronger interaction with more intensified TY Chan-Hom entering the path of the Kuroshio Current of SST 31 °C, which could supply additional moisture through thermal convection of water vapor into its system. Then, further interaction between the rapidly developed TY Nangka following behind and the MLCT enhanced the transfer of moisture and momentum fluxes from Chan-Hom into Linfa. Finally, after STS Linfa made landfall on the Chinese coast, it decayed into a weak low-pressure system before its dissipating, due to the weakening of its cyclonic circulation through the increased friction by the shallower sea bottom and the surrounding lands. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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18 pages, 4717 KiB

Open AccessArticle

Friction Velocity and Aerodynamic Drag Coefficient Retrieval from Sentinel-1 IW Cross-Polarization C-SAR Images under Hurricane Conditions

by Olga Ermakova, Nikita Rusakov, Evgeny Poplavsky, Daniil Sergeev and Yuliya Troitskaya

Remote Sens. 2023, 15(8), 1985; https://doi.org/10.3390/rs15081985 - 09 Apr 2023

Cited by 1 | Viewed by 1480

Abstract

This study presents an approach for friction velocity and aerodynamic drag coefficient retrieval utilizing C-band VH SAR observations from Sentinel-1. The dataset contained 14 SAR images collected under six hurricane scenes co-analyzed with stepped frequency microwave radiometer (SFMR) measurements. The basis for creating this approach utilizes the results proposed earlier linking the parameters of the atmospheric boundary layer from GPS-dropsondes data to the ocean surface emissivity from SFMR measurements. The obtained dependencies of the ocean surface emissivity on surface friction velocity, aerodynamic drag coefficient, and surface wind speed are analyzed together with the collocated SAR data leading to the new GMF valid for the retrieval of friction velocities ranging from 0.55–1.56 m/s and drag coefficient values ranging from 0.00076–0.00232 for all sub swaths. Within the framework of the proposed approach, dependences of the normalized radar cross-section on the surface wind speed were also obtained and used for comparison with existing GMFs to show that the proposed approach is valid. A good consistency was obtained when comparing our results with H14_E and MS1A. As an example the distributions of friction velocity, drag coefficient, and surface wind speed retrieved from the Hurricane Maria SAR image (23 September 2017) were considered. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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18 pages, 18279 KiB

Open AccessArticle

On Surface Waves Generated by Extra-Tropical Cyclones—Part I: Multi-Satellite Measurements

by Vahid Cheshm Siyahi, Vladimir Kudryavtsev, Maria Yurovskaya, Fabrice Collard and Bertrand Chapron

Remote Sens. 2023, 15(7), 1940; https://doi.org/10.3390/rs15071940 - 05 Apr 2023

Cited by 1 | Viewed by 1358

Abstract

Surface waves generated by Extra-Tropical Cyclones (ETCs) can significantly affect shipping, fishing, offshore oil and gas production, and other marine activities. This paper presents the results of a satellite data-based investigation of wind waves generated by two North Atlantic ETCs. These ETCs were fast-moving systems, inhibiting resonance (synchronism) between the group velocity of the generated waves and the ETC translation velocity. In these cases, wave generation begins when the front boundary of the storm appears at a given ocean location point. Since developing waves are slow, they move backward relative to the storm, grow in time, and then leave the ETC stormy area through the rear sector. Multi-satellite observations confirm such a paradigm, revealing that the storm regions are filled with young developing wind waves, the most developed in the rear-right sector. As observed, the energy of these waves grew in time during the ETC life span. It is demonstrated that the extended-fetch concept (inherent for Tropical Cyclones) does not apply to ETC. Instead, by analogy, the concept of extended-duration wave growth is more relevant. Satellite observations confirmed the validity of duration-laws for waves generated by ETCs, and demonstrated that extended-fetch solutioncan be valid at time scales exceeding the lifespan of considered ETCs. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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24 pages, 20967 KiB

Open AccessArticle

Assessment and Calibration of ERA5 Severe Winds in the Atlantic Ocean Using Satellite Data

by Ricardo M. Campos, Carolina B. Gramcianinov, Ricardo de Camargo and Pedro L. da Silva Dias

Remote Sens. 2022, 14(19), 4918; https://doi.org/10.3390/rs14194918 - 01 Oct 2022

Cited by 17 | Viewed by 3410

Abstract

In this paper, we analyze the surface winds of ECMWF ERA5 reanalysis in the Atlantic Ocean. The first part addresses a reanalysis validation, studying the spatial distribution of the errors and the performance as a function of the percentiles, with a further investigation under cyclonic conditions. The second part proposes and compares two calibration models, a simple least-squares linear regression (LR) and the quantile mapping method (QM). Our results indicate that ERA5 provides high-quality winds for non-extreme conditions, especially at the eastern boundaries, with bias between −0.5 and 0.3 m/s and RMSE below 1.5 m/s. The reanalysis errors are site-dependent, where large RMSE and severe underestimation are found in tropical latitudes and locations following the warm currents. The most extreme winds in tropical cyclones show the worst results, with RMSE above 5 m/s. Apart from these areas, the strong winds at extratropical locations are well represented. The bias-correction models have proven to be very efficient in removing systematic bias. The LR works well for low-to-mild wind intensities while the QM is better for the upper percentiles and winds above 15 m/s—an improvement of 10% in RMSE and 50% for the bias compared to the original reanalysis is reported. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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24 pages, 6203 KiB

Open AccessArticle

Surface Wave Developments under Tropical Cyclone Goni (2020): Multi-Satellite Observations and Parametric Model Comparisons

by Maria Yurovskaya, Vladimir Kudryavtsev, Alexey Mironov, Alexis Mouche, Fabrice Collard and Bertrand Chapron

Remote Sens. 2022, 14(9), 2032; https://doi.org/10.3390/rs14092032 - 23 Apr 2022

Cited by 11 | Viewed by 2410

Abstract

Over the Philippine Sea, the tropical cyclone (TC) Goni reaches category 5 on 29–31 October 2020. Multi-satellite observations, including CFOSAT SWIM/SCAT and Sentinel-1 SAR data, are jointly analyzed to assess the performances of a parametric model. Recently developed to provide a fast estimation of surface wave developments under rapidly evolving TCs, this full 2D parametric model (KYCM) and its simplified self-similar solutions (TC-wave geophysical model function (TCW GMF)) are thoroughly compared with satellite observations. TCW GMF provides immediate first-guess estimates, at any location in space and time, for the significant wave height, wavelength, and wave direction parameters. Moving cyclones trigger strong asymmetrical wave fields, associated to a resonance between wave group velocity and TC heading velocity. For TC Goni, this effect is well evidenced and captured, leading to extreme waves reaching up to 8 m, further outrunning as swell systems with wavelengths about 200–250 m in the TC heading direction, slightly shifted leftwards. Considering wind field constrained with very highly resolved Sentinel-1 SAR measurements and medium resolution CFOSAT SCAT data, quantitative agreements between satellite measurements and KYCM/TCW GMF results are obtained. Far from the TC inner core (∼10 radii of maximum wind speed), the superposition of outrunning swell systems and local wind waves estimates leads to Hs values very close to altimeter measurements. This case study demonstrates the promising capabilities to combine multi-satellite observations, with analytical self-similar solutions to advance improved understandings of surface wave generation under extreme wind conditions. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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20 pages, 12881 KiB

Open AccessArticle

Ka-Band Doppler Scatterometry: A Strong Wind Case Study

by Yury Yu. Yurovsky, Vladimir N. Kudryavtsev, Semyon A. Grodsky and Bertrand Chapron

Remote Sens. 2022, 14(6), 1348; https://doi.org/10.3390/rs14061348 - 10 Mar 2022

Cited by 2 | Viewed by 2228

Abstract

Global joint measurements of sea surface winds and currents are planned using satellite-based Doppler scatterometers operating in the Ka-band to achieve improved spatial resolution and retrieval accuracy. Still, the knowledge of sea surface Ka-band backscatter properties is poor, particularly, at high winds (>20 [...] Read more.

^{- 1}

). Sea surface radar cross-section in the Ka-band, in contrast to that in the lower frequency Ku-/X-/C-/L-bands, is likely more sensitive to sea spray, small-scale particles typically present at high winds. In this paper, tower-based field data collected by a continuous dual-co-polarized Ka-band radar during a strong offshore wind event (with wind speed reaching 33 m s

^{- 1}

) are analyzed. This katabatic wind event (≈12 h long) was also recorded by supplementary wave, wind, and current sensors. At the wave fetch of ≈1 km, the maximum wavelength of observed offshore waves was ≈10 m. For such extremely young wind–sea conditions, an apparent sea spray generation was observed during wind gusts. Radar measurements were performed at 20

^{\circ}

and 45

^{\circ}

incidence angles, mostly for cross- and up-wind azimuth look geometry. Based on these high wind measurements, the previously developed Ka-band empirical model is tested and compared with other published geophysical model functions. Dual-co-polarized measurements are used to infer resonant Bragg and non-Bragg scattering components and assess the short wind wave spectrum, which shows a clear tendency for saturation at high winds. The presence of sea spray signatures is apparent in the high-frequency tails of radar Doppler spectra, but their overall contribution to the Doppler centroid frequency is weak. Hence, the standard modulation transfer function approach developed for moderate winds is still applicable at high winds for interpreting the wave-induced Doppler velocity and inferring sea surface currents. These results can also be useful for understanding Doppler scatterometry measurements in tropical cyclones. Full article

(This article belongs to the Special Issue Remote Sensing of Wave Fields under Extreme Weather Conditions (in Tropical and Extra-Tropical Cyclones and Polar Lows))

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