A MATLAB-based Kriged Kalman Filter software for interpolating missing data in GNSS coordinate time series     

Ning Liu  Wujiao Dai  Rock Santerre  Cuilin Kuang 《GPS Solutions》2018,22(1):25

GNSS coordinate time series data for permanent reference stations often suffer from random, or even continuous, missing data. Missing data interpolation is necessary due to the fact that some data processing methods require evenly spaced data. Traditional missing data interpolation methods usually use single point time series, without considering spatial correlations between points. We present a MATLAB software for dynamic spatiotemporal interpolation of GNSS missing data based on the Kriged Kalman Filter model. With the graphical user interface, users can load source GNSS data, set parameters, view the interpolated series and save the final results. The SCIGN GPS data indicate that the software is an effective tool for GNSS coordinate time series missing data interpolation.  相似文献   

Initial results of centralized autonomous orbit determination of the new-generation BDS satellites with inter-satellite link measurements   总被引：3，自引：0，他引：3  

Chengpan Tang  Xiaogong Hu  Shanshi Zhou  Li Liu  Junyang Pan  Liucheng Chen  Rui Guo  Lingfeng Zhu  Guangming Hu  Xiaojie Li  Feng He  Zhiqiao Chang 《Journal of Geodesy》2018,92(10):1155-1169

Autonomous orbit determination is the ability of navigation satellites to estimate the orbit parameters on-board using inter-satellite link (ISL) measurements. This study mainly focuses on data processing of the ISL measurements as a new measurement type and its application on the centralized autonomous orbit determination of the new-generation Beidou navigation satellite system satellites for the first time. The ISL measurements are dual one-way measurements that follow a time division multiple access (TDMA) structure. The ranging error of the ISL measurements is less than 0.25 ns. This paper proposes a derivation approach to the satellite clock offsets and the geometric distances from TDMA dual one-way measurements without a loss of accuracy. The derived clock offsets are used for time synchronization, and the derived geometry distances are used for autonomous orbit determination. The clock offsets from the ISL measurements are consistent with the L-band two-way satellite, and time–frequency transfer clock measurements and the detrended residuals vary within 0.5 ns. The centralized autonomous orbit determination is conducted in a batch mode on a ground-capable server for the feasibility study. Constant hardware delays are present in the geometric distances and become the largest source of error in the autonomous orbit determination. Therefore, the hardware delays are estimated simultaneously with the satellite orbits. To avoid uncertainties in the constellation orientation, a ground anchor station that “observes” the satellites with on-board ISL payloads is introduced into the orbit determination. The root-mean-square values of orbit determination residuals are within 10.0 cm, and the standard deviation of the estimated ISL hardware delays is within 0.2 ns. The accuracy of the autonomous orbits is evaluated by analysis of overlap comparison and the satellite laser ranging (SLR) residuals and is compared with the accuracy of the L-band orbits. The results indicate that the radial overlap differences between the autonomous orbits are less than 15.0 cm for the inclined geosynchronous orbit (IGSO) satellites and less than 10.0 cm for the MEO satellites. The SLR residuals are approximately 15.0 cm for the IGSO satellites and approximately 10.0 cm for the MEO satellites, representing an improvement over the L-band orbits.  相似文献   

Understanding Third Pole Atmospheric Dynamics and Land Surface Processes and Their Associations with the Cryosphere,Air Quality,and Climate Change     

Yun Qian  Hailong Wang  Chuanfeng Zhao  Chun Zhao  Siyu Chen  Xiao-Ming Hu  Shichang Kang 《大气科学进展》2022,39(7):1017-1020

  相似文献   

豫北“21·7”极端暴雨过程特征及成因分析   总被引：1，自引：0，他引：1  

苏爱芳  席乐  吕晓娜  崔丽曼  张宁 《气象》2022,48(5):556-570

利用探空、地面自动站、多普勒雷达等观测资料及ERA5再分析产品,对2021年7月17—22日豫北地区的极端暴雨过程进行分析。结果表明,极端暴雨过程具有强降水持续时间长、降水强度极端及地形影响明显等特征。极端暴雨过程发生于稳定的大尺度天气形势下,在日本海高压西伸及台风烟花(2106号)、查帕卡(2107号)西北行背景下,黄淮低涡外围加强北上的东南急流/偏南急流为强降水的发生提供了异常充足的水汽、能量条件,对流层中低层暖湿平流强迫、叠加地形影响的强动力辐合抬升作用及低空弱冷空气扩散南下是形成强降水的重要条件,而大气“强-弱-强-弱”的对流不稳定层结特征转化说明强降水过程中存在着两种互补的物理机制。不同阶段极端短时强降水(小时降水量≥50 mm)对流系统的形态结构和发展演变特征不同,但从雷达回波的垂直分布来看,系统均具有“低质心”特征,质心强度≥55 dBz且≥50 dBz强回波垂直伸展至5～8 km、持续时间1 h以上。强降水对流系统在太行山前30 km左右范围内的后向发展特征明显,一方面与地面西行偏东风/东北风在太行山绕流作用下形成的地形辐合线不断南伸有关,另一方面也与强降水冷池效应促使...  相似文献   

Effects of land cover type conversion on water exchange and climate change in the source area of the Yellow River     

Wang  Lijuan  Guo  Ni  Sha  Sha  Yang  Yang  Wang  Xiaoping  Hu  Die 《Theoretical and Applied Climatology》2022,149(1-2):525-536

Theoretical and Applied Climatology - The surface radiation and energy flux in the source area of the Yellow River are estimated by using the Moderate Resolution Imaging Spectroradiometer products...  相似文献   

Changes in air pollutants during the COVID-19 lockdown in Beijing:Insights from a machine-learning technique and implications for future control policy          下载免费PDF全文

Jiabao Hu  Yuepeng Pan  Yuexin He  Xiyuan Chi  Qianqian Zhang  Tao Song  Weishou Shen 《大气和海洋科学快报》2021,14(4):63-69

基于2015-2020年北京35个环境空气站和20个气象站观测资料,应用机器学习方法(随机森林算法)分离了气象条件和源排放对大气污染物浓度的影响.结果发现,为应对疫情采取的隔离措施使北京2020年春节期间大气污染物浓度降低了35.1％-51.8％;其中,背景站氮氧化物和一氧化碳浓度的降幅最大,超过了以往报道较多的交通站点.同时,2020年春节期间的气象条件不利于污染物扩散,导致多次霾污染事件发生.为进一步改善北京空气质量,未来需要优化减排策略.  相似文献   

两方程湍流模型对内背风波数值模拟的影响          下载免费PDF全文

Xuhui Hu  Xuefeng Zhang  Lei Lin  Lianxin Zhang  Shifan Wang 《大气和海洋科学快报》2021,14(5):30-36

为了深入理解非静力近似下的波-湍相互作用问题,本研究在σ坐标的海洋环境研究和预报模型(MERF)中引入常用的Mellor-Yamada两方程湍混合参数化方案(MY2.5),评估垂向湍混合对小尺度背风波传播过程的影响.瞬时状态场的模拟结果表明,无论是否为非静力近似条件,上述湍参数化方案的引入都会减弱背风波传播的模拟效果.从时间平均场的试验结果来看,垂向湍混合过程会显著减小非静力近似和静力近似之间的差异.此外,能量收支分析的诊断结果表明,MY2.5方案会显著抑制陆坡地形下的背风波传播过程,进而将更多的潮能转化到不可逆的湍混合过程中.  相似文献   

Characterization,modeling, and remediation of karst in a changing environment     

Zexuan Xu  Nicolas Massei  Ingrid Padilla  Andrew Hartmann  Bill Hu 《Environmental Earth Sciences》2018,77(12):476

This introductory editorial paper provides a review and prospective outlook of the achievements and challenges in karst research under a changing environment. A brief discussion of the past and future karst research has been focused on: (1) data and new technologies; (2) modeling of karst flow and reactive transport; (3) responses of karst hydrosystems to climate variability and changes across scales.  相似文献   

Spatial and temporal analyses of air pollutants and meteorological driving forces in Beijing–Tianjin–Hebei region,China     

Zizhan Hu  Xuguang Tang  Chen Zheng  Menglin Guan  Jingwei Shen 《Environmental Earth Sciences》2018,77(14):540

Due to its negative impact on the living environment of human beings, ambient air pollution has become a global challenge to human health. In this study, surface observations of six criteria air pollutants, including PM_2.5, PM₁₀, SO₂, NO₂, CO and O₃, were collected to investigate the spatial and temporal variation in the Beijing–Tianjin–Hebei (BTH) region during 2013–2016 and to explore the relationships between atmospheric pollutants and meteorological variables using quantile regression model (QRM) and multiple linear regression model (MLRM). The results show that BTH region has experienced significant air pollution, and the southern part generally has more severe conditions. The annual average indicates clear decreasing trends of the particulate matters, SO₂ and CO concentrations over the last 4 years and slight increasing trends of NO₂ and O₃ in several cities. The seasonal and monthly characteristics indicate that the concentrations of five species reach their maxima in the winter and their minima in the summer, whereas O₃ has the opposite behaviour. Finally, the pseudo R² values show that the QRMs have the best performance in the winter, followed by spring, fall, and summer. Specifically, all the meteorological factors have significant impacts on air pollution but change with pollutants and seasons. The MLRM results are generally consistent with the QRM results in all seasons, and the inconsistencies are more common in the fall and winter. The results of this research provide foundational knowledge for predicting the response of air quality to climate change in the BTH region.  相似文献   

Extreme deformation characteristics and countermeasures for a tunnel in difficult grounds in southern Shaanxi,China     

Jinxing Lai  Xiuling Wang  Junling Qiu  Jianxun Chen  Zhinan Hu  Hao Wang 《Environmental Earth Sciences》2018,77(19):706

The Qingling–Bashan (QB) mountain region in southern Shaanxi mainly consists of strongly compressive zones from east to west, with tight folds and compressive fractures. There is a wide distribution of soft rocks of various types, such as phyllite and slate, accompanied by complex geological structures. Ironically, tunnel construction in these difficult grounds with complicated geological conditions embraces a high risk of extreme deformation due to various unpredictable reasons, which can frequently cause collapse and result in budget overruns during the construction period. Therefore, it is crucial to conduct effective countermeasures to eliminate or avoid such adverse impacts. This paper provides a case study on the “Yingfeng tunnel” (a tunnel constructed in soft rock consisting of a slate ground) based on a geological survey, indoor experiments and in situ monitoring. A successive rock mass deformation resulted in the tunnel lining seriously intruding into construction clearance and some other sections, even collapsing during the construction. The maximum displacement amount was 62.5 cm, while the maximum deformation speed reached as high as 34.18 mm/day. Additionally, to evaluate the construction impacts of tunnelling-induced geo-hazards, an investigation on extreme deformation was conducted. Considering the time-dependent features of the rock mass deformation, the constraint-convergence method was used to put forward applicable countermeasures in this paper. Finally, from the feedbacks of monitoring results, extreme deformation of the Yingfeng tunnel was effectively controlled.  相似文献