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Retrieval of Antarctic sea ice freeboard and thickness from HY-2B satellite altimeter data

Acta Oceanologica Sinica 2024年第3期43卷 87-101页

作者： Yizhuo Chen Xiaoping Pang Qing Ji Zhongnan Yan Zeyu Liang Chenlei Zhang Chinese Antarctic Center of surveying and mapping Wuhan UniversityWuhan 430079China key laboratory of polar surveying and mapping science Ministry of Natural ResourcesWuhan 430079China key laboratory of polar Environment Monitoring and Public Governance Ministry of EducationWuhan 430079China 4 School of Geography and Tourism Anhui Normal UniversityWuhu 241002China

Antarctic sea ice is an important part of the Earth’s atmospheric system,and satellite remote sensing is an important technology for observing Antarctic sea *** Chinese Haiyang-2B(HY-2B)satellite altimeter data could be used to estimate sea ice freeboard and provide alternative Antarctic sea ice thickness information with a high precision and long time series,as other radar altimetry satellites can,needs further *** paper proposed an algorithm to discriminate leads and then retrieve sea ice freeboard and thickness from HY-2B radar altimeter *** first collected the Moderate-resolution Imaging Spectroradiometer ice surface temperature(IST)product from the National Aeronautics and Space Administration to extract leads from the Antarctic waters and verified their accuracy through Sentinel-1 Synthetic Aperture Radar ***,a surface classification decision tree was generated for HY-2B satellite altimeter measurements of the Antarctic waters to extract leads and calculate local sea surface *** then estimated the Antarctic sea ice freeboard and thickness based on local sea surface heights and the static equilibrium ***,the retrieved HY-2B Antarctic sea ice thickness was compared with the CryoSat-2 sea ice thickness and the Antarctic Sea Ice Processes and Climate(ASPeCt)ship-based observed sea ice *** results indicate that our classification decision tree constructed for HY-2B satellite altimeter measurements was reasonable,and the root mean square error of the obtained sea ice thickness compared to the ship measurements was 0.62 *** proposed sea ice thickness algorithm for the HY-2B radar satellite fills a gap in this application domain for the HY-series satellites and can be a complement to existing Antarctic sea ice thickness products;this algorithm could provide long-time-series and large-scale sea ice thickness data that contribute to research on global climate change.

关键词： HY-2B satellite altimeter classification decision tree sea ice freeboard and thickness Antarctic waters

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Real-time Rescue Target Detection Based on UAV Imagery for Flood Emergency Response

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Journal of Geodesy and Geoinformation science 2024年第1期7卷 74-89页

作者： ZHAO Bofei SUI Haigang ZHU Yihao LIU Chang WANG Wentao state key laboratory of Information Engineering in surveying Mapping and Remote SensingWuhan UniversityWuhan 430079China

Timely acquisition of rescue target information is critical for emergency response after a flood *** Aerial Vehicles(UAVs)equipped with remote sensing capabilities offer distinct advantages,including high-resolution imagery and exceptional mobility,making them well suited for monitoring flood extent and identifying rescue targets during ***,there are some challenges in interpreting rescue information in real time from flood images captured by UAVs,such as the complexity of the scenarios of UAV images,the lack of flood rescue target detection datasets and the limited real-time processing capabilities of the airborne on-board ***,we propose a real-time rescue target detection method for UAVs that is capable of efficiently delineating flood extent and identifying rescue targets(i.e.,pedestrians and vehicles trapped by floods).The proposed method achieves real-time rescue information extraction for UAV platforms by lightweight processing and fusion of flood extent extraction model and target detection *** flood inundation range is extracted by the proposed method in real time and detects targets such as people and vehicles to be rescued based on this *** experimental results demonstrate that the Intersection over Union(IoU)for flood water extraction reaches an impressive 80%,and the IoU for real-time flood water extraction stands at a commendable 76.4%.The information on flood stricken targets extracted by this method in real time can be used for flood emergency rescue.

关键词： UAV flood extraction target rescue detection real time

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Demand and key technology for a LEO constellation as augmentation of satellite navigation systems

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Satellite Navigation 2024年第1期5卷 1-9页

作者： Yuanxi Yang Yue Mao Xia Ren Xiaolin Jia Bjiao Sun Xi’an Research Institute of surveying and mapping Xi’an710054ShaanxiChina state National key laboratory of Geo-Information Engineering Xi’an710054ShaanxiChina

A Low Earth Orbit(LEO)constellation augmenting satellite navigation is important in the future development of Global Navigation Satellite System(GNSS).GNSS augmented by LEO constellations can improve not only the accuracy of Positioning,Navigation,and Timing(PNT),but also the consistency and reliability of secure PNT *** paper mainly analyzes the diverse demands of different PNT users for LEO augmented GNSS,including the precision demand in real-time,the availability demand in special areas,the navigation signal enhancement demand in complex electromagnetic environments,and the integrity demand with high ***,the possible contributions of LEO constellations to PNT performance are analyzed from multiple aspects.A particular attention is paid to the special PNT user requirements that cannot be fulfilled with existing GNSS,such as the PNT service demand in the polar regions and the onboard GNSS orbit determination demand of some LEO *** key technologies to be considered in the constellation design,function realization,and payload development of the LEO-augmented navigation system are summarized.

关键词： Low earth orbit navigation constellation Accuracy augmentation Orbit determination Integrity

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Long-term variation of Arctic Sudden Stratospheric Warmings(SSW) and potential causes

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Earth and Planetary Physics 2024年第5期8卷 742-752页

作者： QingRan Li ShaoDong Zhang KaiMing Huang ChunMing Huang Yun Gong WenTao Tang Zheng Ma School of Electronic Information Wuhan University Guizhou Normal University key laboratory of Geospace Environment and Geodesy Ministry of Education state key laboratory of Information Engineering in surveying Mapping and Remote Sensing School of Electronic Information Engineering Jingchu University of Technology

Utilizing the European Centre for Medium-Range Weather Forecast(ECMWF) Reanalysis v5(ERA5), for the first time, we have confirmed close links among Sudden Stratospheric Warmings(SSWs) in the Northern Hemisphere(NH), the polar vortices, and stratospheric Planetary Waves(PWs) by analyzing and comparing their trends. Interestingly, within overall increasing trends, the duration and strength of SSWs exhibit increasing and decreasing trends before and after the winter of 2002, respectively. To reveal possible physical mechanisms driving these trends, we analyzed the long-term trends of the winter(from December to February) polar vortices and of stratospheric PWs with zonal wave number 1. Notably, our results show that in all three time periods(the entire period of 41winters, 1980 to 2020, and the two subperiods — 1980-2002 and 2002-2020) enhancing SSWs were always accompanied by weakening winter polar vortices and strengthening polar PWs like Stationary Planetary Waves(SPWs) and 16-day waves, and vice versa. This is the first proof, based on ERA5 long-term trend data, that weakening polar vortices and enhancing stratospheric PWs(especially SPWs) could cause an increase in SSWs.

关键词： sudden stratospheric warmings stationary planetary waves 16-day waves polar vortrices long-term trend correlation coefficient

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Status and trends in the stability of the three largest ice shelves in Antarctica

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science China Earth sciences 2024年第8期67卷 2615-2632页

作者： Rongxing LI Guojun LI Lu AN Menglian XIA Da LV Yuan CHENG Aiguo ZHAO Tian CHANG Xiangbin CUI Shengkai ZHANG Shijie LIU Yixiang TIAN Weian WANG Center for Spatial Information science and Sustainable Development Applications Tongji UniversityShanghai 200092China College of surveying and Geo-informatics Tongji UniversityShanghai 200092China Postdoctoral Research Station of Shanghai surveying and mapping Institute Shanghai 200063China key laboratory of Spatial-temporal Big Data Analysis and Application of Natural Resources in Megacities Shanghai 200063China Institute for Conservation of Cultural Heritage School of Cultural Heritage and Information ManagementShanghai UniversityShanghai 200444China polar Research Institute of China Shanghai 200136China Chinese Antarctic Center of surveying and mapping Wuhan UniversityWuhan 430079China

The Ross,Filchner-Ronne,and Amery ice shelves are the three largest ice shelves in Antarctica,playing a crucial role in supporting the Antarctic ice ***,current studies on the stability of the three largest ice shelves primarily focus on singular or limited factors,lacking a comprehensive assessment of multiple *** systematically and in-depth study the stability and trend of the three largest ice shelves,we comprehensively collected and analyzed key parameters,including elevation changes,basal melting,surface meltwater,major rifts propagation rate,suture zones,ice front area change rate,grounding lines,ice velocity,and mass ***,we selected the collapsed Larsen B Ice Shelf(LBIS),the rapidly changing and structurally weakened Pine Island Ice Shelf(PIIS),and the accelerating Totten Ice Shelf(TIS)as reference ice *** comparing and analyzing the key parameters between these reference ice shelves and the three largest ice shelves,we find the status and trends in the stability of the *** findings reveal that most key parameters of the three largest ice shelves present relatively minor variations compared to those of the reference ice ***,50%of the parameters are smaller than those of the accelerating TIS,88%are smaller than those of the rapidly changing PIIS,and all parameters are smaller than those of the collapsed ***,after analyzing parameters that are not smaller than those of the TIS,it is observed that they remain in a stable ***,the three largest ice shelves are currently undergoing natural changes that do not threaten their stability in the short ***,the evolution of the ice shelves under global climate change remains uncertain,making long-term observation and monitoring essential to assess their impact on sea level rise.

关键词： Three largest ice shelves in Antarctica key parameters Remote sensing monitoring Ice shelf stability Sea level change

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Hourly land surface temperature retrieval over the Tibetan Plateau using Geo-LightGBM framework: Fusion of Himawari-8 satellite, ERA5 and site observations

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Advances in Climate Change Research 2024年第4期15卷 623-635页

作者： Zhao-Hua LIU Shan-Shan WENG Zhao-Liang ZENG Ming-Hu DING Ya-Qiang WANG Zhehao LIANG Civil and surveying&mapping Engineering Jiangxi University of Science and TechnologyGanzhou 341000China state key laboratory of Severe Weather Chinese Academy of Meteoroogical sciences Beijing 100081China Space Geodesy and Geoinformation Technical Unviersity of BerlinBerlin 10623Germany

The Tibetan Plateau(TP)is highly sensitive to even minor fluctuations in land surface temperature(LST),which can result in permafrost melting and degradation of alpine grasslands,leading to serious ecological ***,it is crucial to have high-temporal-resolution and seamless hourly estimating and monitoring of LST for a better understanding of climate change on the ***,we employed Himawari-8 satellite,Digital Elevation Model(DEM),ERA5 reanalysis and meteorological station observations data to develop a new LightGBM framework(called Geo-LightGBM)for estimating LST on the TP,and then analyzed the spatiotemporal variations of those ***-LightGBM demonstrated excellent LST estimation accuracy,with an R2(coefficient of determination)of 0.971,RMSE(root-mean-square error)of 2.479℃,and MAE(mean absolute error)of 1.510℃.The estimated LST values for the year 2020 agreed well with observed values,with remarkable differences in hourly LST ***,the estimated LST was more accurate than that from ***,there were two high LST centers,located in the Yarlung Zangbo River Basin and the Qaidam Basin,and a low LST center located in the central *** SHAP(SHapley Additive exPlanations)and correlation analyses revealed DSCS(the mean ground downward shortwave radiation under clear-sky conditions)to be the most importantly input variable for estimating *** dummy variables(e.g.,longitude,latitude,DEM)were also found to be crucial for model accuracy *** findings indicate the potential for constructing a high-precision and seamless 24-h LST real-time retrieval and monitoring platform for the TP by combining satellite and China's independently developed CLDAS(China Land Data Assimilation System)data in future.

关键词： Tibetan Plateau Himawari-8 ERA5 Land surface temperature Geo-LightGBM

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Monitoring Surface Deformation Using Distributed Scatterers InSAR

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Journal of Geodesy and Geoinformation science 2024年第1期7卷 42-58页

作者： LI Haocheng DONG Jie WANG Yi’an LIAO Mingsheng state key laboratory of Information Engineering in surveying Mapping and Remote SensingWuhan UniversityWuhan 430079China School of Remote Sensing and Information Engineering Wuhan UniversityWuhan 430079China

In the past two decades,extensive and in-depth research has been conducted on Time Series InSAR technology with the advancement of high-performance SAR satellites and the accumulation of big SAR *** introduction of distributed scatterers in Distributed Scatterers InSAR(DS-InSAR)has significantly expanded the application scenarios of InSAR geodetic measurement by increasing the number of measurement *** study traces the history of DS-InSAR,presents the definition and characteristics of distributed scatterers,and focuses on exploring the relationships and distinctions among proposed algorithms in two crucial steps:statistically homogeneous pixel selection and phase ***,the latest research progress in this field is tracked and the possible development direction in the future is *** simulation experiments and two real InSAR case studies,the proposed algorithms are compared and verified,and the advantages of DS-InSAR in deformation measurement practice are *** work not only offers insights into current trends and focal points for theoretical research on DS-InSAR but also provides practical cases and guidance for applied research.

关键词： InSAR permanent scatterers distributed scatterers statistically homogeneous pixel selection phase optimization

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The variation in basal channels and basal melt rates of Pine Island Ice Shelf

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Acta Oceanologica Sinica 2024年第1期43卷 22-34页

作者： Mingliang Liu Zemin Wang Baojun Zhang Xiangyu Song Jiachun An Chinese Antarctic Center of surveying and mapping Wuhan UniversityWuhan 430079China key laboratory of polar Environment Monitoring and Public Governance(Wuhan University) Ministry of EducationWuhan 430079China School of Civil Engineering Shijiazhuang Tiedao UniversityShijiazhuang 050043China key laboratory of Roads and Railway Engineering Safety Control(Shijiazhuang Tiedao University) Ministry of EducationShijiazhuang 050043China

In recent years,there has been a significant acceleration in the thinning,calving and retreat of the Pine Island Ice Shelf(PIIS).The basal channels,results of enhanced basal melting,have the potential to significantly impact the stability of the *** this study,we used a variety of remote sensing data,including Landsat,REMA DEM,ICESat-1 and ICESat-2 satellite altimetry observations,and Ice Bridge airborne measurements,to study the spatiotemporal changes in the basal channels from 2003 to 2020 and basal melt rate from 2010 to 2017 of the PIIS under the Eulerian *** found that the basal channels are highly developed in the PIIS,with a total length exceeding 450 *** of the basal channels are ocean-sourced or groundingline-sourced basal channels,caused by the rapid melting under the ice shelf or near the groundingline.A raised seabed prevented warm water intrusion into the eastern branch of the PIIS,resulting in a lower basal melt rate in that *** contrast,a deepsea trough facilitates warm seawater into the mainstream and the western branch of the PIIS,resulting in a higher basal melt rate in the main-stream,and the surface elevation changes above the basal channels of the mainstream and western branch are more *** El Ni?o event in 2015–2016 possibly slowed down the basal melting of the PIIS by modulating wind field,surface sea temperature and depth seawater *** and atmospheric changes were driven by El Ni?o,which can further explain and confirm the changes in the basal melting of the PIIS.

关键词： Pine Island Ice Shelf basal channel basal melt rate digital elevation models(DEMs) satellite altimetry

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Precise orbit determination for Tianwen-1 during mapping phase

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Astrodynamics 2024年第3期8卷 471-481页

作者： Shanhong Liu Jing Kong Jianfeng Cao Hao Huang Haijun Man Jianguo Yan Xie Li National key laboratory of science and Technology on Aerospace Flight Dynamics Beijing100094China Beijing Aerospace Control Center Beijing100094China Institute for Frontiers in Astronomy and Astrophysics Bejing Normal UniversityBeijing100875China Astronomy Department Bejing Normal UniversityBeijing100875China state key laboratory of Information Engineering in surveying Mapping and Remote SensingWuhan UniversityWuhan430079China

The mapping phase is a key stage of the Tianwen-1 orbiter. It has the longest exploration time and gathers abundant radio tracking data via the Chinese deep space network. Thus, it also provides opportunities for radio science research topics such as the Mars gravity field model, ephemeris, and radio occultation experiments. At this stage, the need for imaging takes the highest priority, leading to frequent attitude adjustments for the spacecraft, which presents challenges for Precise Orbit Determination (POD). To improve the accuracy of the spacecraft’s orbit, this study analyzes the effects of arc length, the empirical acceleration, and the solar radiation pressure parameters on POD, considering the limited number of radio tracking observations. For one-day arcs, the POD is not able to adequately account for wheel off-loading and a few unknown forces with limited observations, but reasonable fitting is performed for the wheel off-loading occurring during tracking periods or the gap between two tracking periods. When extending the POD arc to three days, the estimated empirical acceleration can be well-fitted and reflects the aggregation feature, but the solar radiation pressure parameter has little impact on POD results. The root mean square of two-way range-rate residuals after POD is about 0.18-0.35 mm/s;the orbital position accuracy of 60% of the arcs is better than 100 m.

关键词： empirical acceleration mapping phase precise orbit determination(POD) radio science

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The GNSS PWV retrieval using non-observation meteorological parameters based on ERA5 and its relation with precipitation

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Geodesy and Geodynamics 2024年第3期15卷 302-313页

作者： Weifeng Yang Zhiping Chen Kaiyun Lv Pengfei Xia Tieding Lu School of surveying and Geoinformation Engineering East China University of TechnologyNanchang 330013China key laboratory of Mine Environmental Monitoring and Improving around Poyang Lake of Ministry of Natural Resources East China University of TechnologyNanchang 330013China state key laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China Jiangxi Province Engineering Research Center of surveying Mapping and Geographic InformationNanchang 330025China School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China

The pressure and temperature significantly influence precipitable water vapor(PWV) retrieval. Global Navigation Satellite System(GNSS) PWV retrieval is limited because the GNSS stations lack meteorological sensors. First, this article evaluated the accuracy of pressure and temperature in 68 radiosonde stations in China based on ERA5 Reanalysis data from 2015 to 2019 and compared them with GPT3model. Then, the accuracy of pressure and temperature calculated by ERA5 were estimated in 5 representative IGS stations in China. And the PWV calculated by these meteorological parameters from ERA5(ERA5-PWV) were analyzed. Finally, the relation between ERA5-PWV and precipitation was deeply explored using wavelet coherence analysis in IGS stations. These results indicate that the accuracy of pressure and temperature of ERA5 is better than the GPT3 model. In radiosonde stations, the mean BIAS and MAE of pressure and temperature in ERA5 are-0.41/1.15 hpa and-0.97/2.12 K. And the mean RMSEs are 1.35 hpa and 2.87 K, which improve 74.77% and 40.58% compared with GPT3 model. The errors of pressure and temperature of ERA5 are smaller than the GPT3 model in bjfs, hksl and wuh2, and the accuracy of ERA5-PWV is improved by 18.77% compared with the GPT3 model. In addition, there is a significant positive correlation between ERA5-PWV and precipitation. And precipitation is always associated with the sharp rise of ERA5-PWV, which provides important references for rainfall prediction.

关键词： ERA5 GNSS Precipitable water vapor Precipitation Wavelet coherence analysis

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