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Project titleMulti-source satellite observations and modeling of typhoon-ocean interaction

KeywordsOcean remote sensing, Typhoon, Air-Sea interaction, Upper-ocean response, Wind waves, Atmospheric and ocean modelling

Annotation
Typhoons are extreme weather events that usually generate strong winds, waves, rainfall, storm surges and flooding. These natural disasters bring enormous threats to coastal activities and human living. Though the Russia is far from the tropical zone, the need in typhoons investigations and prediction is justified by their not rare appearance at the Sakhalin Island and the Primorye. Latest observations revealed more frequent transformation of Tropical Cyclones (TCs) to the extratropical cyclones, which also bring strong damage to the Russian coastal infrastructure. To reduce their influence, improved prediction and early warning of typhoon intensity, radius and track motion are necessary. This urges an advanced understanding of typhoon dynamics and its interaction with the ocean surface, where many different types and scales of physical processes occur. While much progress has been made in the past decades, joint analysis of typhoon-ocean system using satellite remote sensing and numerical modelling still remains relatively untapped. This proposal aims to bridge the gap of ocean remote sensing with numerical modeling through the knotted cooperation between the two Chinese and Russian science teams. The project firstly targets to establish a synergistic observation chain of typhoon over the ocean for various variables including wind, wave, current, temperature and salinity. These parameters are essential to explore the parameterization solutions of wind-wave and fluxes for typhoon air-sea interactions, and to better understand the upper ocean response and feedback mechanisms to typhoon, which constitute another goal of this project. This joint Chinese-Russian proposal is organized with the three work packages that are led by both team principal investigators. The first work package focuses on development of an improved surface wave (short wind waves and dominant ones) and wave breaking models, and a wind-over-wave coupled model providing description of the momentum-heat-moisture exchange at high winds conditions. The former will be used to predict the microwave scattering and emission from ocean surface in the typhoon areas that is compared with the satellite multi-sensor measurements in the second work package. The third work package centers on the typhoon wind-wave-current processes in terms of the spatial features, inner corrections and relationships with typhoon properties. The main accent is done on the typhoon-ocean interactions by exploring the improved transfer coefficients between air and sea (developed in the first work package), the responses and feedback of the upper ocean dynamics and thermodynamics as well as the physical mechanisms of rapid typhoon intensity changes. The objectives of this ambitious proposal may be reached only by combining the experience and strengths of the two science teams. Both team principal investigators have contributed significantly to the typhoon studies, particularly in satellite remote sensing field by Chinese team and physical modeling field by Russian team. The success of this joint scientific project will advance our techniques of typhoon microwave remote sensing, understanding of typhoon-ocean interactions, and capabilities of improving typhoon track and intensity predictions.

Expected results
Typhoons are extreme weather events characterized by high winds, abnormally high waves, intense precipitation, storm surges and floods. They cause catastrophic damage to the inhabitants of the coastal zone and its infrastructure. In spite of the remoteness of Russia from the tropical zone, the actuality of the typhoon study and development of methods for their trajectory and intensity prediction is associated with their frequent outfall onto Sakhalin Island and Primorsky Krai. The development of methods for monitoring and forecasting typhoon generation presents an extremely actual task, which solution will significantly reduce the impact of typhoons and associated extratropical cyclones on the people and coastal infrastructure. An effective solution to this problem requires a deep understanding of the typhoon dynamics and their interaction with the oceanic surface, characterized, in its turn, by various and different-scale physical processes. The main goal of this project is to bridge the existing gap between the ocean remote sensing and ocean dynamics modeling. The expected results are: 1. Semi-empirical model of the short waves spectrum (in the range of wavelengths from millimeters to tens of meters) and characteristics of breaking wave crests, suitable for hurricane wind conditions; the results of testing the model using satellite co-polarized radar observations; conclusion about the reliability of the model. 2. A model of the air-sea interaction in hurricane winds, which describes the contribution of wind waves and wave braking to the heat, moisture and momentum transfer on the sea surface, and takes into account the wave crest breaking and generating the splashes under the Kelvin-Helmholtz instability conditions; testing the model using the measurement data on drag and heat/moisture transfer coefficients, available in the literature; conclusions about the reliability of the model. 3. Parameterization of model results in the form of momentum and heat/moisture transfer coefficients in hurricane winds; implementation of these parameterizations into the WRF model; modeling the evolution of observed typhoons, conclusions on the advantages of the new parameterization for typhoon modeling. 4. A two-dimensional parametric model describing the generation of waves and evolution of their parameters (energy, spectral peak frequency and direction) in typhoons/hurricanes and the results of model verification using empirical data on wave distributions published in the literature. 5. Results of modeling the observed distributions of waves in typhoons, establishing patterns of the wave fields and their dependences on the typhoon/hurricane parameters (wind speed, speed of propagation, radius). 6. Self-similar distributions of wave parameters in hurricanes/typhoons, and their representation in a form convenient for subsequent scientific and practical use. 7. A quad-pol scattering model combining scattering from the regular surface (TSM and SSA-2) and breaking waves (Kirchhoff's approximation) based on the description of surface in hurricane winds developed in the project. 8. Results of comparison of model results with the data of quad-pol radar measurements in hurricane winds, assessment of the contribution of wave breaking to the backscattering, interpretation of the co- and cross-polarized scattering in hurricanes. 9. Database of tropical cyclones for the period 2019 - 2021 with collocated AMSR2 radiometer satellite measurements of microwave radiation, scatterometer measurements of radar scattering, wind fields derived from satellite data and airborne SFMR radiometer wind measurements. 10. Model of the brightness temperature of the ocean - atmosphere system microwave radiation for the AMSR2 measurement parameters. 11. Parameterizations for estimating atmospheric radiation parameters through the parameters of the atmosphere and ocean. 12. Experimental geophysical model functions for C- and X-band frequencies for the AMSR2 observation angle for moderate and strong winds. 13. Microwave radiation model based on the radar scattering model and the physical sea surface model, validated using AMSR2 measurements at C- and X-band frequencies in tropical cyclones. 14. A database of sea surface temperature, salinity, level and current anomalies during typhoons/hurricanes from combined satellite active microwave measurements and data on typhoon tracks and vertical ocean stratification. 15. Empirical relationships between the characteristics of sea surface anomalies of temperature, salinity, level and currents (amplitude, shape, asymmetry) with TC parameters (wind speed, speed of propagation, radius) and ocean stratification. 16. Results of the analysis of satellite observations of typhoon wakes on the sea surface using analytical and numerical models of the ocean response, taking into account the "standard" and new (created in the project) parameterizations of the drag and heat/moisture transfer coefficients. Recommendations for further development of the models. Obtaining these results will ensure significant progress in the development of methods for satellite microwave monitoring of typhoons, understanding the physics of typhoon interaction with the ocean, which will finally lead to a significant improvement in predicting the typhoon intensity and trajectories and, consequently, minimize their damage to the people and coastal infrastructure.

Annotation of the results obtained in 2023
In the final third year of the Russian-Chinese RSF project “Integrated satellite observations and modeling of the interaction of the ocean with typhoons” the following results were obtained: - Investigation of waves generated by extratropical cyclones (ETCs) in the North Atlantic based on multi-sensor satellite measurements (Sentinel-3A, Sentinel-3B, AltiKa, CryoSat-2, JASON-3, CFOSAT-SWIM) and modeling using parametric wave models was completed. Data from satellite measurements and modeling have shown that the generation of waves in fast-moving ETCs begins at their leading front, at the trailing front the waves reach their maximum development, and then leave the storm area in the form of a swell. For quick estimates of wave parameters in the ETC, self-similar solutions based on the idea of “extended-duration wave growth” have been proposed. A comparison of the parametric wave model, which used hourly wind fields from the NCEP/CSFv2 reanalysis as an input parameter, with satellite measurements showed that the model provides a reliable and detailed description of the spatiotemporal wave field generated by the ETC. It was found that the heights and wavelengths in the WTC reach extremely large values - 18 m and 500 m, respectively. It has been established that the attenuation of swell energy with distance from the storm area is inversely proportional to the distance traveled. - The wave parametric model is generalized to the case of taking into account the generation and propagation of waves under conditions of inhomogeneous ocean currents. The main characteristic of currents that influences the evolution of waves is the vorticity of the currents, which bends the trajectories of the waves, causing them to focus/defocus and corresponding changes in energy. Calculations of the evolution of waves on “real” ocean currents in the North Atlantic were carried out. It was found that when waves propagate against the current, the effect of wave trapping by the current occurs with an anomalous increase in wave energy. The second notable effect is the scattering of wave trajectories by sub- and meso-scale ocean eddies. This scattering leads to local “bursts” of wave energy (caustics) sporadically distributed in space, associated with the focusing of waves during the passage of the vortex. A comparison of wave fields in the North Atlantic with and without currents shows that the effect of currents leads to a 20-25% increase in wave height and length. - Together with Chinese project participants, studies of the features of backscattering of radio waves during hurricane winds were carried out based on quasi-synchronous and spatially combined measurements with the RADARSAT-2 SAR (C-band data on HH and HV polarization) and RCM (Radar Constellation Mission, C-band data on VH and VV polarization). Quasi-synchronous SAR measurements were decomposed into resonant (Bragg) scattering and reflections from wind wave breaking. It is shown that Bragg scattering and unpolarized reflections from wave breaking are saturated at high wind speeds. At the same time, the contribution of wave breaking to cross-polarization (HV or VH) during hurricane winds shows a continuous increase. It is shown that reflections of the radar signal from breaking waves account for 40% and 80% of the NRCS at VV- and HH-polarizations, respectively, and 90% of the NRCS for HV- or VH-polarizations. - The model for the formation of the Doppler shift of the SAR signal (DPDop model), developed at the previous stage together with the Chinese participants in the project, was applied to the analysis of the Sentinel-1A SAR measurements of Doppler velocity on the ocean surface in Hurricane Maria in the Atlantic Ocean. Taking into account Doppler shifts caused by wind waves made it possible to estimate current velocities using SAR, which were compared with current measurements by high-frequency coastal radars. Measurement uncertainties (RMSE 0.19 m/s) demonstrated the ability to obtain reliable estimates of ocean current velocities in high wind conditions. - A comparison was made of the cyclone parameters obtained from satellite measurements by the Russian MTVZA-GYA and Japanese AMSR2 with the ERA5 reanalysis data. It is shown that the maximum wind speed in the TC according to MTVZA-GYa data for cyclones with intensity below category 3 turned out to be lower than according to AMSR2 data by an average of 7%, and for cyclones of categories 4 and 5 – by 10%, which corresponds to the difference between the spatial resolution of wind fields. Thus, MTVZA-GY measurements can be used to study the dynamics of TC development, but taking into account the underestimation of their intensity. ERA5 data underestimates hurricane force winds by an average of 13% and maximum winds by 27%. - As a result of statistical analysis of satellite altimetry observations, patterns of formation of the sea level anomaly were established depending on the intensity of TC and the speed of their movement. In particular: deeper surface depressions correspond to stronger and slower moving TCs; the centers of the depressions are located near the center of the TC, and the depths of the depressions attenuate in the direction normal to the trajectory. The previously constructed semi-empirical model is applied to estimate SSH anomalies caused by TCs, where the input parameters are TC parameters and real ocean stratification. It is shown that the semi-empirical model generally agrees well with satellite altimeter measurements. - As a result of the analysis of satellite measurements of SST anomalies caused by TCs, it was found that the depth of the mixed layer (ML) under the TC, normalized by wind speed, Coriolis parameter and buoyancy frequency, is a universal function of the dimensionless speed of TC movement (the speed of TC movement normalized by the radius of the TC and the Coriolis parameter ). The dependence of the dimensionless depth on the dimensionless speed of movement of the TC is close to a power law with an exponent of -0.5. - Checking the dependence of the normalized ML depth on other dimensionless parameters characterizing the TC and its influence on the upper layer of the ocean revealed only a dependence on the ratio of the buoyancy frequency to the Coriolis parameter. The dependence, although weak, was approximated by a power law with an exponent of -0.19. The inclusion of this dependence in the ML depth parameterization led to improved comparison of the model with satellite SST anomalies caused by TCs in all regions of the World Ocean. - The barotropic response of sea surface height (SSH) to the passage of polar cyclones (PLs) is investigated using satellite altimetry measurements (CryoSat-2, Saral, and Sentinel-3) and simulations using a simplified model. It was found that the SSH anomalies along the altimeter tracks had the shape of a depression centered near the PC trajectory. Observations and the model showed that the largest negative SSH anomalies were observed in areas where the speed of movement of the PL was minimal, and the trajectory of its movement had a radius of curvature much smaller than the barotropic radius of deformation. Quasi-geostrophic current velocities corresponding to SSH anomalies in the PL wakes reached 0.15 m/s, which is comparable to current velocities observed in the Barents Sea. The results of work at this stage were published in 5 articles in journals indexed in WoS and Scopus included in Q1: two articles in Transactions on Geoscience and Remote Sensing (DOI 10.1109/TGRS.2023.3235829; DOI 10.1109/TGRS.2023.3246771), three articles in Remote Sensing (https://doi.org/10.3390/rs15071940; https://doi.org/10.3390/rs15092377; https://doi.org/10.3390/rs15174239). Three other articles presenting the results of the stage have been submitted for publication in the journals indexed in WoS and Scopus included in Q1: Geophysical Research Letter, Geoscience and Remote Sensing Letters, and Transactions on Geoscience and Remote Sensing, where they are currently at the “minor revision” stage. Five of these eight articles were prepared in co-authorship by participants of the Russian-Chinese RSF project.

Publications

1. Shengren Fan, Biao Zhang, Artem Moiseev, Vladimir Kudryavtsev, Johnny A. Johannessen, and Bertrand Chapron On the Use of Dual Co-polarized Radar Data to Derive a Sea Surface Doppler Model Part 2: Simulation and Validation Transactions on Geoscience and Remote Sensing, doi: 10.1109/TGRS.2023.3246771 (year - 2023) https://doi.org/10.1109/TGRS.2023.3246771

2. Vahid Cheshm Siyahi, Vladimir Kudryavtsev, Maria Yurovskaya, Fabrice Collard and Bertrand Chapron On Surface Waves Generated by Extra-Tropical Cyclones - Part I: Multi-Satellite Measurements Remote Sensing, Т. 15, 1940 (year - 2023) https://doi.org/10.3390/rs15071940

3. Vahid Cheshm Siyahi, Vladimir Kudryavtsev, Maria Yurovskaya, Fabrice Collard and Bertrand Chapron On Surface Waves Generated by Extra-Tropical Cyclones - Part II: Simulations Remote Sensing, Т. 15, 2377 (year - 2023) https://doi.org/10.3390/rs15092377

4. Vladimir Kudryavtsev, Anastasiia Stokoz and Kirill Khvorostovsky On Barotropic Response of Arctic Seas to Polar Lows: A Case Study in the Barents Sea Remote Sensing, Т. 15, 4239 (year - 2023) https://doi.org/10.3390/rs15174239

5. Vladimir Kudryavtsev, Shengren Fan, Biao Zhang, Bertrand Chapron, Johnny A. Johannessen and Artem Moiseev On the Use of Dual Co-polarized Radar Data to Derive a Sea Surface Doppler Model Part 1: Approach Transactions on Geoscience and Remote Sensing, doi: 10.1109/TGRS.2023.3235829 (year - 2023) https://doi.org/10.1109/TGRS.2023.3235829

Annotation of the results obtained in 2021
The project aims to investigate the interaction between the ocean and tropical cyclones (TCs) using integrated satellite microwave measurements. Various, but interrelated aspects of this problem are investigated, namely: - wind waves and wave breakings, which determine the momentum and heat fluxes, as well as radar backscatter and radiation of the ocean surface under hurricane winds; - generation and propagation of dominant surface waves in the TC area; - barotropic and baroclinic response of the ocean to the passage of the TC. The final goal of these studies is the development of methods for operational monitoring and forecasting of the evolution of typhoons / hurricanes based on satellite microwave data and modeling. In the first year of the project, the following results were obtained: - On the basis of experimental studies of the spectral peak wave breakings, it was found that the parameters of the breakings (length of breakings, their area) are proportional to the steepness of the peak waves in the cube and do not depend on the wind speed. The established patterns correspond to the parameterization of energy dissipation due to breakings, used in the parametric model of waves in hurricanes. - A semi-empirical model of the wind wave breakings, which combines the breakings of the spectral peak wave breakings and the equilibrium interval, was developed. The model allows to interpret the previously unexplained scatter in the observational data of the breaking parameters under various wind-wave conditions. The main purpose of the model is its use in the analysis and interpretation of microwave measurements (SMOS, SMAP) in hurricanes. - A model of the atmospheric boundary layer under strong winds has been developed, taking into account the effect of waves ("regular" and breaking) on turbulent heat and momentum fluxes, as well as the effect of sea spray on the momentum balance due to the "vortex force", leading to the acceleration of the air flow by falling drops at their movement through shear of wind speed. Preliminary calculations have shown that the considered spray effect may explain the drag coefficient decrease and the heat transfer coefficient increase observed experimentally on the ocean surface during hurricane winds. - A model of the growth rate of spectral peak waves for moderate and hurricane winds is proposed, taking into account the effect of aerodynamic roughness modulations. It is shown that the suppression of roughness modulations under strong winds leads to a decrease in the growth rate of the spectral peak waves. Parametrization of this effect is included in the hurricane wave generation model. - A 2-D parametric model of wave generation and propagation in an inhomogeneous wind field in the tropical and extra-tropical cyclones, and polar lows has been developed. The model is completely self-consistent and describes the evolution of the main wave parameters (energy, peak frequency and its direction) taking into account the wind effect, nonlinear interactions and dissipation due to breakings. Testing the model has demonstrated its adequacy to the measured data. The parametric model is adapted to the Arctic conditions, including the generation of waves by polar lows (PL). Testing the model on the satellite altimeter data and in-situ measurements on the platform demonstrated the adequacy of the model. Cases of abnormally high waves in the Arctic associated with the condition of resonance between the waves and the motion of the PL, similar to what occurs in the TC, have been found. On the basis of experimental studies carried out with the use of a Doppler radar and a video camera, estimates of the normalized radar cross section (sigma0) of wave breaking were obtained. A semi-empirical model of the sigma0 of "individual breaking " and the contribution of the ensemble of wave breakings to the sigma0 of the surface is proposed, which is in good agreement with the measurement data. This model is further used as a component of the full sigma0 model of the sea surface, which includes Bragg scattering and specular reflections. The model of the short waves spectrum, implemented in a 2-D Bragg model, demonstrated good agreement with the measurements of the VV-HH polarization difference in the Ku-band, obtained both from geophysical model functions (GMF), and direct measurements from the French-Chinese CFOSAT satellite for the wind speeds from 3 to 20 m/s. This comparison confirmed the reliability of the model, and justifies the possibility of its application for the strong winds conditions. A radar scattering model describing both the sigma0 and the Doppler frequency shift, taking into account the breakings, was provided to the Chinese team for testing and studying the Doppler shifts on the sea surface, measured from 4 polarization SAR data from Sentinel 1A, -1B, and their relationship with ocean currents. - A database has been created for 68 TCs in the Northwest Pacific from January 2019 to September 2021, consisting of the AMSR2 radiometer data of the Level 1R, the ASCAT full resolution data of scatterometer, images of the MODIS spectroradiometer from the Aqua and Terra satellites, SARAL altimeter, daily average SST and the upper ocean layer salinity data, ASCAT wind field data. The database contains information from the best track dataset, maximum wind speed and minimum pressure. The work on creating a geo-information system - a portal - for visualization of satellite measurements and products for typhoon research is ongoing. - The model of Tb of the ocean-atmosphere system microwave radiation for AMSR2 measurements is modified. The model is based on solving the equation of radiation transfer in a non-scattering atmosphere and uses refined models of microwave absorption in oxygen and water vapor, as well as recently developed geophysical model functions of the ocean emissivity dependence on wind speed, applicable under conditions of tropical cyclones. On the basis of the analysis of the model results and the fields of Tb in the TCs, a criterion for the ratio of measurements at different frequencies to exclude from consideration the areas with signal scattering by cloudy, raindrops and ice crystals was obtained. - Parametrizations for estimating atmospheric parameters of radiation using the parameters of the moisture content of the atmosphere - the water vapour content (WVC) and the liquid water content of the clouds (LWC) have been obtained. The obtained parameterizations are used to calculate the atmospheric parameters of microwave radiation from the satellite measurements of Tb by the AMSR2 radiometer in tropical cyclones using the WVC and LWC estimates obtained by applying the previously developed neural network algorithms. A database of anomalies of the sea surface temperature, salinity and ocean surface level in the wake of hurricanes / typhoons, the trajectories of which pass through the freshened ocean waters caused by the Amazon river, has been created. Significant changes in the vertical structure of the ocean on small spatial scales will make it possible to study the baroclinic response of the ocean to the passage of a hurricane, and to analyze the influence of the “barrier layer”, which has an important effect on hurricane intensity, on the formation of the hurricane wake in the SST. A preliminary analysis showed that temperature and salinity anomalies are shifted to the right of the cyclone trajectory, salinity anomalies are wider than temperature anomalies, and the depth of anomalies is related to the cyclone propagation speed and the wind speed. To study the barotropic response of the ocean to the passage of cyclones in which baroclinic processes are insignificant, a database of the wakes of the polar lows (PL) at the ocean level has been created. The preliminary analysis showed that the depth of the level anomalies in the wake of the PLs increases with an increase in wind speed and a decrease in the speed of the cyclone propagation, and decreases with an increase in the radius of the cyclone. The values of the level anomalies increase with decreasing ocean depth; this explains the fact that the most pronounced level anomalies in the wake of cyclones were found in the Barents Sea. In the Barents Sea, the average value of level anomalies in the wake of the cyclone is 0.2-0.4 m, in some cases reaching 0.8 m. The results of the first year of the project were published in 2 papers in the Journal Geophysical Research Ocean Journal (Q1), in 2 papers in the Remote Sensing Journal (Q1), in 3 papers in the proceedings of the IGARSS-2021 conference (indexed by SCOPUS), in one paper in the proceedings of the PIERS-2021 conference (indexed by SCOPUS), and one paper in the Ecology and Hydrometeorology Journal (which is in the list of the Higher Attestation Commission). The presentation and paper presented by the team member, PhD student V. Cheshm Siyahi at the PIERS-2021 conference, was awarded as the "Best Student Paper Award".

Publications

1. Fabrice Ardhuin, Matias Alday, Maria Yurovskaya Total Surface Current Vector and Shear From a Sequence of Satellite Images: Effect of Waves in Opposite Directions Journal of Geophysical Research: Oceans, Т. 126, вып. 7, с.1-26 (year - 2021) https://doi.org/10.1029/2021JC017342

2. Maria Yurovskaya, Vladimir Kudryavtsev, Bertrand Chapron Assessment And Monitoring Of High Sea State Generated By Tropical Cyclones 2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS Proceedings, doi: 10.1109/IGARSS47720.2021.9553293 (year - 2021) https://doi.org/10.1109/IGARSS47720.2021.9553293

3. Pavel D. Pivaev, Vladimir N. Kudryavtsev, Aleksandr E. Korinenko, Vladimir V. Malinovsky Field Observations of Breaking of Dominant Surface Waves Remote Sensing, Т. 13 (16), 3321 (year - 2021) https://doi.org/10.3390/rs13163321

4. V. Cheshm Siyahi, V. N. Kudryavtsev, M. V. Yurovskaya Surface Waves Generated by Polar Lows: Satellite Observations and Simulations Progress in Electromagnetics Research Symposium (PIERS 2021), - (year - 2021)

5. V. Cheshm Siyahi, V. N. Kudryavtsev, M. V. Yurovskaya Параметрическая модель поверхностных волн в приложении к Арктическим морям Гидрометеорология и экология, № 64, с. 515-530 (year - 2021) https://doi.org/10.33933/2713-3001-2021-64-515-530

6. Vladimir Kudryavtsev, Maria Yurovskaya, Bertrand Chapron Self-Similarity of Surface Wave Developments Under Tropical Cyclones Journal of Geophysical Research: Oceans, Т.126, вып. 4, c.1-31 (year - 2021) https://doi.org/10.1029/2020JC016916

7. Yury Yu. Yurovsky, Vladimir N. Kudryavtsev, Semyon A. Grodsky, Bertrand Chapron Ka-Band Radar Cross-Section of Breaking Wind Waves Remote Sensing, Т.13, вып.10, 1929 (year - 2021) https://doi.org/10.3390/rs13101929

8. Yury Yu. Yurovsky, Vladimir N. Kudryavtsev, Semyon A. Grodsky, Bertrand Chapron Ka-Band Radar Backscattering From Breaking Wind Waves 2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS Proceedings, doi: 10.1109/IGARSS47720.2021.9553284 (year - 2021) https://doi.org/10.1109/IGARSS47720.2021.9553284

9. Zabolotskikh Elizaveta, Chapron Bertrand Estimation Of The Atmospheric Microwave Radiation Parameters In Tropical Cyclones From The AMSR2 Measurement Data 2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS Proceedings, doi:10.1109/IGARSS47720.2021.9553892 (year - 2021) https://doi.org/10.1109/IGARSS47720.2021.9553892

10. - База данных тропических циклонов для северо-западной части Тихого океана за 2019-2021 гг. -, - (year - )

Annotation of the results obtained in 2022
The joint Russian-Chinese project aims to study the interaction of the ocean with tropical cyclones (typhoons / hurricanes) based on satellite measurements and modeling with the aim of further practical implementation of research results in satellite operational monitoring and forecasting of the development / evolution of hazardous atmospheric phenomena and their impact on coastal infrastructure. In the second year of the project, the following results were obtained: - The fields of surface waves generated by polar lows (PL) and extratropical cyclones (EC) were studied based on measurements from the Sentinel-3A, Sentinel-3B, Jason-3, CryoSat-2, AltiKa and CFOSAT-SWIM satellites and modeling using 2- D parametric model. It is shown that the heights and wavelengths generated by cyclones are much higher than the "expected" values determined by the wind speed and radius. In the PL, the waves reach heights of 8m-12m, and in the EC - heights of 18-20m and length - 500m. Anomalous values of the wave parameters are due to the effect of synchronism between the generated waves and the moving wind field. The good agreement of the model with the satellite data indicates the possibility of its application as a tool for studying and predicting waves in extreme conditions. (see model matching with CFOSAT-SWIM http://www.youtube.com/watch?v=T7w3dLCQ4yo https://www.youtube.com/watch?v=OjqL5L9e4OE) - It has been established that due to the asymmetry of the wind fields in the PL (having the comma shape), the wave parameters strongly depend on the location of the storm zone relative to the direction of its movement. If the storm is located in the right sector of the PL, then the waves, moving along with the cyclone, receive more energy and their heights reach anomalously high values. PLs are short-lived cyclones, therefore, in contrast to tropical cyclones (TCs), the development of waves in PLs depends strongly on the PL lifetime. Automodeling solutions are proposed that make it possible to carry out quick estimates of heights and wavelengths for a limited set of PL parameters: wind speed, radius, movement speed, lifetime (see examples of calculations for PL https://www.youtube.com/watch?v=StsYyurGg7U , for EC https://www.youtube.com/watch?v=zIowAsvkHlU). - Based on the application of the scattering model to the analysis of synchronous observations of the Epsilon hurricane with the RADARSAT-2 SAR (VV and HH polarizations) and the recently launched SAR Radar Constellation Mission (RCM) operating on the HH and HV polarizations, it has been established that the relative contribution of wave breaking to the RCS at VV and HH polarizations at incidence angles of 40-50 deg is 40% for VV and 65% for HH, and reaches 80% for cross polarization. The effect of saturation of short Bragg waves with hurricane winds has been found. The contribution of wave breaking at HH and VV polarizations demonstrates a trend towards saturation, which, however, is absent at the cross polarization, which will be the subject of a more detailed study. - A model has been developed for calculating the Doppler shift (DS) of the radar signal reflected from the sea surface based on the RCS measurements on VV and HH polarizations (DPDop model, Dual co-Polarized Doppler velocity model). The input parameter of the DPDop model is the spectrum of surface waves (or integral parameters of the spectrum) and the geometry of radar observations. The model was tested on direct DS measurements with the Sentinel-1B SAR in the VV mode at angles of incidence of 24° and 37° combined with in situ measurements of the wave and wind spectrum from ocean buoys, and demonstrated its adequacy (error −0.24 Hz, rms error - 5.55 Hz). Similar results were obtained by comparing the model with DS measurements from Sentinel-1B on a global scale (World Ocean), where WAVEWATCH-3 and ECMWF reanalysis data on waves and wind were used as input parameters for DPDop. - The DPDop model was applied to subtract the contribution of surface waves to the DS measured with the Sentinel-1B SAR, and thereby obtain the true current velocities. Comparison of the currents retrieved from the DS with in situ measurements by high-frequency coastal radars gave a systematic bias of −0.04 m/s and a root-mean-square error of 0.15 m/s, which confirms the possibility of using the DPDop model to retrieve ocean current fields from satellite measurements. - Software developed for processing Level 1R AMSR2 data in order to calculate the ocean emissivity using parametrizations of the dependence of atmospheric emission parameters on atmospheric water vapor content parameters. Compilation of the 2019-2021 typhoon database has been completed, consisting of processed AMSR2 data over typhoon tracks and collocated wind speeds ranging from moderate to hurricane values. The geophysical model functions of the dependence of the increment of ocean emission on the see surface wind speed for C- and X-band frequencies for the AMSR2 observation angle for moderate and strong winds are obtained. - Using the created software, the MTVZA-GY measurement data from April to December 2021 were processed and a database of collocated with the AMSR2 measurements with a time difference not exceeding 30 minutes was created. The AMSR2 measurements were processed by the algorithm for retrieving the sea surface wind speed, and the wind fields were compared with the Tb of the ocean microwave emission on 10.6 GHz channels, calculated based on the MTVZA-GY measurements and ERA5 reanalysis data to take into account the atmospheric components of the emission. - Based on a database of satellite measurements of temperature and salinity anomalies (SST and SSS), data on TC parameters, the vertical thermohaline structure of the ocean, and data on precipitation rates, an analysis of ocean response on passage of seven TC observed in the Amazon and Orinoco plume regions was carried out. It has been established that SST and SSS anomalies in the TC wake increase with an increase in wind speed, a decrease in the TC propagation speed, and dipping of the thermocline; when the TC passes over the river plume, the SSS anomalies are the largest. The effect of intense precipitation in TCs on the thermohaline response is insignificant. It is shown that SST and SSS anomalies normalized to the appropriate scales (including wind speed, Brent-Väisälä frequency, Coriolis parameter, and temperature (salinity) gradient in the seasonal thermocline) are universal functions of the TC Rossby number. - Based on the database of satellite and in situ observations for 417 TCs in the period from 2010 to 2020 throughout the World Ocean, the quality of the ocean response for the TCs passage model used in the project was assessed. It has been established that the model adequately reproduces the SSS anomalies in the TC wake, but overestimates the SST anomalies, which is most pronounced for the eastern part of the Pacific Ocean. A comparison of the simulated mixed layer thickness with the Argo float data showed that the model overestimated the thickness, which could explain the overestimation of the temperature anomalies. An analysis of the observations together with the results of modeling using different parameterizations of the drag coefficient showed that the optimal parameterization is the one that results in the saturation of wind stress during hurricane winds. Research results are presented at international conferences: (i) European Geosciences Union (EGU-2022), (ii) International Geoscience and Remote Sensing Symposium (IGARSS-2022); (iii) Progress In Electromagnetics Research Symposium (PIERS); (iv) XIX conference "Modern problems of remote sensing of the Earth from space". Research results are published in: - two articles in international journals from the first quartile, Q1: “Boundary-Layer Meteorology” (issue dedicated to the memory of S.S. Zilitinkevich) and “Remote Sensing”, - two articles in the Proceedings of the conference “IGARSS-2022 Proceedings” (included in the SCOPUS citation database). The results of the joint study of the Russian and Chinese teams were submitted as two articles to the journal from the first quartile, Q1: “IEEE Transactions in Geoscience and Remote Sensing”, and are currently being finalized (the first article is “minor revision”, the second article is “major revision").

Publications

1. Cheshm Siyahi V., Kudryavtsev V.N., Yurovskaya M.V. On Big Waves Under Polar Lows Based On Altimeter Measurements And Model Simulations 2022 IEEE International Geoscience and Remote Sensing Symposium IGARSS Proceedings, doi: 10.1109/IGARSS46834.2022.9883477 (year - 2022) https://doi.org/10.1109/IGARSS46834.2022.9883477

2. Pavel Pivaev, Vladimir Kudryavtsev, Nicolas Reul, Bertrand Chapron Upper Ocean Response To Tropical Cyclones From Observations And Modelling 2022 IEEE International Geoscience and Remote Sensing Symposium IGARSS Proceedings, doi: 10.1109/IGARSS46834.2022.9884843 (year - 2022) https://doi.org/10.1109/IGARSS46834.2022.9884843

3. Vladimir Kudryavtsev, Vahid Cheshm Siyahi, Maria Yurovskaya, Bertrand Chapron On Surface Waves in Arctic Seas Boundary-Layer Meteorology, published online; doi: 10.1007/s10546-022-00768-9 (year - 2022) https://doi.org/10.1007/s10546-022-00768-9

4. Yury Yu. Yurovsky, Arseny A. Kubryakov, Evgeny V. Plotnikov, Pavel N. Lishaev Submesoscale Currents from UAV: An Experiment over Small-Scale Eddies in the Coastal Black Sea Remote Sensing, Т. 14 (14), 3364 (year - 2022) https://doi.org/10.3390/rs14143364