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Measurement analyses and evaluations of sea-level heights using the HY-2A satellite’s radar altimeter

Acta Oceanologica Sinica 2019年第11期38卷 134-139页

作者： Xingwei jiang yongjun jia Youguang Zhang National Satellite Ocean Application Service Beijing 100081China Key Laboratory of Space Ocean Remote Sensing and Application(MNR) Beijing 100081China

The HY-2A satellite is China’s first independent oceanic dynamic environmental satellite,and has been operating continuously for more than six *** satellite’s radar altimeter,which is one of the main loads on the satellite,has the ability to realize all-weather and all-day observations of global sea-surface heights,as well as significant wave heights and sea-surface wind *** observed data have been widely used in marine disaster prevention and reduction,along with resource development,maritime security and other *** order to achieve a comprehensive understanding of the multi-year overall observational performances of the HY-2A satellite’s radar altimeter,all of the observational data of the IGDR product from October 26,2012 to August 27,2017 were selected in this study for a comprehensive *** height measurement capability of the HY-2A satellite’s radar altimeter was evaluated using self-crossover and Jason-2 crossover *** height discrepancies at the self-crossover point of the HY-2A satellite’s ascending and descending orbits were also *** was found that for the HY-2A satellite’s radar altimeter in global waters under the restriction conditions of ascending and descending orbits,the height anomaly differences were within a range of less than 30 *** absolute mean error was determined to be 5.81 cm,and the height anomaly standard deviation was 7.76 *** the conditions of the observational areas being limited within a scope of 60°from the Equator,it was determined that the sea-level height anomaly differences were less than 10 cm at the junction of the ascending and descending orbits,the absolute mean error was 3.95 *** addition,the sea-level height anomaly standard deviation was observed to be *** a mutual cross method with the Jason-2 satellite,it was found that under the conditions of the observational area being within the scope of 66°from the equator,the height anomaly differences at the junction

关键词： HY-2A satellite radar altimeter sea level anomalies

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The numerical simulation of the Kuroshio frontal eddies in the East China Sea using a hybrid coordinate ocean mode

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Acta Oceanologica Sinica 2013年第5期32卷 31-41页

作者： jia yongjun ZHANG Youguang LIN Mingsen National Satellite Ocean Application Service State Oceanic Administion

A hybrid coordinate ocean model （ltYCOM） is used to simulate the Kuroshio frontal eddies in the East China Sea （ECS）. The research area is located （20°-32°N, 120°-132°E）. Using tile simulating data, it is figured out that the Kuroshio frontal eddies occur in summer as well as in the other season in this area. The life cycle of the Kuroshio and its frontal eddies is different with the position. The life-cycle of the Kuroshio frontal eddies of the northwest Diaoyu Islands is about 14 d; and the life cycle of the Kuroshio frontal eddies of southwest Yakushima about 20 d. This result extends the in situ researching results greatly. In addition, the vertical impact depth of the Kuroshio frontal eddies is also changing with the position. On the whole, in the ECS, the maximum impact depth of the Kuroshio frontal eddies of the northwest Taiwan Islands is about 75 m; the maximum impact depth of the Kuroshio frontal eddies of the northwest Diaoyu Islands is more than 125 m, but no more than 200 m; and the maximum impact depth of the Kuroshio frontal eddies of southwest Yakushima is up to 100 m.

关键词： Kuroshio frontal eddies hybrid coordinate ocean model East China Sea

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Preliminary results of the global ocean tide derived from HY-2A radar altimeter data

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Acta Oceanologica Sinica 2023年第2期42卷 65-73页

作者： Jungang Yang yongjun jia Chenqing Fan Wei Cui Lab of Marine Physics and Remote Sensing First Institute of OceanographyMinistry of Natural ResourcesQingdao266061China National Satellite Ocean Application Service Beijing100081China

The HY-2A satellite,which is equipped with a radar altimeter and was launched on August 16,2011,is the first Chinese marine dynamic environmental monitoring *** ocean tides is one of the important applications of the radar altimeter *** radar altimeter data of the HY-2A satellite from November 1,2011 to August 16,2014 are used herein to extract global ocean *** constants representing the tidal constituents are extracted by HY-2A RA data with harmonic analysis based on the least squares *** tide aliasing issues,the analysis of the alias periods and alias synodic periods of different tidal constituents shows that only the tidal constituents M_(2),N_(2),and K_(2)are retrieved precisely by the HY-2A RA *** derived tidal constants of the tidal constituents M_(2),N_(2)and K_(2)are compared to those of tidal gauge data and the TPXO tide model *** comparison between the derived results and the tidal gauge data shows that the RMSEs of the tidal amplitude and phase lag are 9.6 cm and 13.34°,2.4 cm and 10.47°,and 8.1 cm and 14.19°for tidal constituents M_(2),N_(2),and K_(2),*** comparisons of the semidiurnal tides with the TPXO model results show that tidal constituents have good consistency with the TPXO model *** findings confirm the good performance of HY-2A RA for retrieving semidiurnal tides in the global ocean.

关键词： HY-2A satellite radar altimeter ocean tide tide analysis

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Estimating the Baseline Error of Wide-Swath Altimeters Using Nadir Altimeters via Numerical Simulation

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Journal of Ocean University of China 2022年第3期21卷 681-693页

作者： MIAO Xiangying jia yongjun LIN Mingsen MIAO Hongli College of Information Science and Engineering Ocean University of ChinaQingdao266100China National Satellite Ocean Application Service(NSOAS) Beijing100081China

The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track *** errors can be identified and estimated in accordance with height differences at crossover points generated with nadir altimeters after excluding the interference from other error *** of the wide-swath altimeter baseline estimation methods considered only the roll error in previous studies.A numerical simulation was conducted in this study using nadir altimeters to estimate the roll and length errors simultaneously to provide a selectable scheme for baseline error estimation and correction for future wide-swath *** based on the parameters of the surface water and ocean topography mission and Sentinel-3A show that the correlation coefficient of the roll error between the estimated and simulated values is 0.89,while the correlation coefficient of the length error is *** sea surface height root mean square error(RMSE)can be reduced from 12.18 cm to 6.45 cm based on the two estimated *** estimation effect can be increased by using multiple nadir altimeters to form an observation *** numerical simulation of the five nadir altimeter constellation shows that the correlation coefficients of the roll and length errors would increase to 0.97,which reduces the sea surface height RMSE to 2.88 *** addition,the stability of this method is indicated in simulation experiments,which introduce different degrees of sea state errors.

关键词： baseline error wide-swath altimeter roll angle baseline length nadir altimeter crossover point height difference

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Estimating significant wave height from SAR imagery based on an SVM regression model

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Acta Oceanologica Sinica 2018年第3期37卷 103-110页

作者： GAO Dong LIU Yongxin MENG Junmin jia yongjun FAN Chenqing College of Electronic and Information Engineering Inner Mongolia University The First Institute of Oceanography State Oceanic Administration National Satellite Ocean Application Service State Oceanic Administration

A new method for estimating significant wave height（SWH） from advanced synthetic aperture radar（ASAR） wave mode data based on a support vector machine（SVM） regression model is presented. The model is established based on a nonlinear relationship between σ0, the variance of the normalized SAR image, SAR image spectrum spectral decomposition parameters and ocean wave SWH. The feature parameters of the SAR images are the input parameters of the SVM regression model, and the SWH provided by the European Centre for Medium-range Weather Forecasts（ECMWF） is the output parameter. On the basis of ASAR matching data set, a particle swarm optimization（PSO） algorithm is used to optimize the input kernel parameters of the SVM regression model and to establish the SVM model. The SWH estimation results yielded by this model are compared with the ECMWF reanalysis data and the buoy data. The RMSE values of the SWH are 0.34 and 0.48 m, and the correlation coefficient is 0.94 and 0.81, respectively. The results show that the SVM regression model is an effective method for estimating the SWH from the SAR data. The advantage of this model is that SAR data may serve as an independent data source for retrieving the SWH, which can avoid the complicated solution process associated with wave spectra.

关键词： advanced synthetic aperture radar wave mode support vector machine significant wave height

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Detection of the Kuroshio frontal instable processes (KFIP) in the East China Sea using the MODIS images

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Acta Oceanologica Sinica 2010年第6期29卷 35-43页

作者： jia yongjun ZHANG Jie National Satellite Ocean Application Service Beijing 100081 China First Institute of Oceanography State Oceanic Administration Qingdao 266061 China

The Kuroshio frontal instable processes （KFIP） in the East China Sea （ECS） not only have a great impact on the hydrologic characteristics,the pollutants drift,the distribution of seafloor sediment and the ships navigation of the ECS,but also are closely related to the climate changes of the coastal areas of the *** the frequency and area of occurrence of the KFIP have not been studied fully and *** of its high spatial and temporal resolution,MODIS data is a kind of very good data source for surveying and researching the KFIP in the *** aim of this study is to detect the KFIP in the ECS by using MODIS data,and to study the frequency and region of occurrence of the KFIP in the *** selection has coverage of level 2 data of MODIS SST and Kd490 ranging from July 1,2002 to June 30,2009 of the ECS when there was no cloud impact or *** using of the data,the minimum standard of the Kuroshio temperature fronts and the diffuse attenuation coefficient （Kd490） fronts of the ECS are *** on these standards and the curvature distinguish methods,the standard of curvature distinguish for the KFIP in the ECS are put *** making use of this standard,we study a total of 2073 satellite-derived images,and discover that as long as there is no cloud impact from January to May and October to December,the KFIP in the ECS are surely found in MODIS satellite *** June to September,the frequency of occurrence can also reach to 82.9% at ***,it is obtained that there are three source regions of these instability processes,namely,（26°N,121.5°E） nearby,（27°N,125°E） nearby and （30°N,128°E） *** differences of the characteristics of these instability processes which are generated in different regions are analyzed in the present study.

关键词： Kuroshio frontal instable processes frequency and region of occurrence East China Sea MODIS

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Nonparametric estimations of the sea state bias for a radar altimeter

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Acta Oceanologica Sinica 2017年第9期36卷 108-113页

作者： MIAO Hongli JING Yujie jia yongjun LIN Mingsen ZHANG Guoshou WANG Guizhong College of Information Science and Engineering Ocean University of China National Satellite Ocean Application Service State Oceanic Administration

To estimate the sea state bias（SSB） for radar altimeter, two nonparametric models, including a Nadaraya-Watson（NW） kernel estimator and a local linear regression（LLR） estimator, are studied based on the Jason-2 altimeter data. Selecting from different combinations of the Gaussian kernel function, spherical Epanechnikov kernel function, a fixed bandwidth and a local adjustable bandwidth, it is observed that the LLR method with the spherical Epanechnikov kernel function and the local adjustable bandwidth is the optimal nonparametric model for the SSB estimation. The comparisons between the nonparametric and parametric models are conducted and the results show that the nonparametric model performs relatively better at high-latitudes of the Northern Hemisphere. This method has been applied to the HY-2A altimeter as well and the same conclusion can be obtained.

关键词： radar altimeter sea state bias significant wave height wind speed nonparametric model parametric model

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Inversion method of deflection of the vertical based on SWOT wide-swath altimeter data

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Geodesy and Geodynamics 2024年第4期15卷 419-428页

作者： Xin Liu Menghao Song Chao Li Guihua Hui Jinyun Guo yongjun jia Heping Sun College of Geodesy and Geomatics Shandong University of Science and TechnologyQingdao 266590China Weicheng Branch of Natural Resources and Planning Bureau of Weifang City Weifang 261021China National Satellite Ocean Application Service Beijing 100081China State Key Laboratoryof Geodesy and Earth's Dynamics Innovation AcademyforPrecision Measurement Science and TechnologyChinese Academy of ScienceWuhan 420071China

The deflection of the vertical(DOV)is the key information in the study of ocean gravity ***,in most areas,the precision of the prime component of DoV is significantly lower than that of the meridian *** obtain higher accuracy and resolution of ocean gravity information,researchers have proposed a novel altimeter called the wide-swath *** altimeter allows for the simultaneous acquisition of high-precision and high-resolution two-dimensional measurements of sea surface height(SSH).In this paper,the Surface Water and Ocean Topography(SWOT)mission with a wide-swath altimeter on board is selected for *** cycle of swoT sea surface height data is simulated to inverse the DOV in the Arabian Sea(45°E—80°E,0°-30°N),and the inversion results are compared with those of conventional altimeter *** results demonstrate that the difference between the meridian and prime components derived from the inversion of swoT wide-swath data is minimal,significantly outperforming the inversion results of conventional nadir altimeter *** advantage of swoT wide-swath altimeter lies in its ability to use the multi-directional geoid slope at any sea surface measurement point to invert the components in the meridian and prime *** investigate the impact of this advantage on inversion precision,this paper employs a method to calculate the gradient of the geoid in multiple directions to invert DoV *** improvement effect of calculating the gradient of the geoid in multiple directions on the precision of DoV component is *** is found that the accuracy of DoV inversion has significantly improved with the increase of geodetic gradient calculation *** addition,the effects of various errors and grid spacing in SwoT wide sea surface height data on the precision of Dov inversion are also analyzed.

关键词： SWOT Wide-swath altimeter Inversion method of Dov Multi-directional Arabian sea

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Classification of ice and water in the Arctic using radar altimeter and microwave radiometer data from HY-2B satellite

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Acta Oceanologica Sinica 2023年第5期42卷 179-191页

作者： Chengfei jiang Mingsen Lin Ruixue Cao Hao Wei Lijian Shi Bin Cheng yongjun jia Qimao Wang School of Marine Science and Technology Tianjin UniversityTianjin 300072China National Satellite Ocean Application Service Ministry of Natural ResourcesBeijing 100081China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China Key Laboratory of Space Ocean Remote Sensing and Application State Oceanic AdministrationBeijing 100081China College of Ocean and Meteorology Guangdong Ocean UniversityZhanjiang 524088China Finnish Meteorological Institute Helsinki FI-00560Finland

Several Chinese marine satellites have been launched in recent *** sea ice and the ocean in the Arctic is of great importance for climate *** ice in the Arctic has changed rapidly during the past few decades with respect to the extent and *** this study,we applied combined passive and active microwave data from the Chinese HaiYang-2B(HY-2B)satellite to classify ice and sea water in the *** use data from a radar altimeter(RA)and a calibration microwave radiometer(CMR)to discriminate between ice and water by applying several approaches(1)the single parameter threshold criteria,(2)the multi-parameters linear segmentations and(3)the K-means *** results yielded by these methods were in good agreement(classification accuracy>95%)with the Satellite Application Facility on Ocean and Sea Ice products between November and *** other months(May–October),however,the agreement was less good(lowest classification accuracy approximate 85%in summer).A hybrid approach combined with graphical ice edges detection and microwave radar waveform analysis is therefore developed.A visual comparison with SAR images suggested the hybrid approach results greatly improved the ice and water discrimination in *** study demonstrated that multi-sensors(RA and CMR)configurations from HY satellites can offer comparable polar earth observation to the European Space Agency and NOAA satellite products.

关键词： Arctic active microwave data passive microwave data sea ice seawater

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Preliminary calibration results of the HY-2B altimeter’s SSH at China’s Wanshan calibration site

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Acta Oceanologica Sinica 2021年第5期40卷 129-140页

作者： Chuntao Chen jianhua Zhu Chaofei Ma Mingsen Lin Longhao Yan Xiaoqi Huang Wanlin Zhai Bo Mu yongjun jia School of Ocean Yantai UniversityYantai 264005China National Ocean Technology Center Ministry of Natural ResourcesTianjin 300112China National Satellite Ocean Application Service Ministry of Natural ResourcesBeijing 100081China

Satellite altimeter needs to be calibrated to evaluate the accuracy of sea surface height *** dedicated altimeter calibration field needs to establish a special calibration strategy and needs to evaluate its calibration *** paper describes absolute calibration of HY-2 B altimeter SSH using the GPS calibration method at the newly Wanshan calibration site,located in the Wanshan Islands,*** are two HY-2 B altimeter passes across the Wanshan calibration *** No.362 is descending and the ground track passes the east of Dan’gan *** No.375 is ascending and crosses the Zhiwan *** GPS data processing strategy of Wanshan calibration site was established and the accuracy of GPS calibration method of Wanshan calibration site was ***,the processing strategies of the HY-2 B altimeter for the Wanshan calibration site were established,and a dedicated geoid model data were used to benefit the calibration *** time-averaged HY-2 B altimeter bias was approximately 2.12 cm with a standard deviation of 2.08 *** performance of the HY-2 B correction microwave radiometer was also evaluated in terms of the wet troposphere path delay and showed a mean difference-0.2 cm with a 1.4 cm standard deviation with respect to the in situ GPS radiosonde.

关键词： calibration HY-2B altimeter Wanshan calibration site GPS buoy

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