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Identifying AMSR-E radio-frequency interference over winter land

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Frontiers of Earth Science 2015年第3期9卷 437-448页

作者： Sibo ZHANG, li guan Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science & Technology Nanjing 210044 China

Satellite microwave emission mixed with signals from active sensors is referred to as radio- frequency interference （RFI）. RFI affects greatly the quality of data and retrieval products from space-bome microwave radiometry. An accurate RFI detection will not only enhance geophysical retrievals over land but also provide evidence of the much-needed protection of the microwave frequency band for satellite remote sensing technologies. It is difficult to detect RFI from space-borne microwave radiometer data over winter land, because RFI signals are usually mixed with snow in mid-high latitudes. A modified principal component analysis （PCA） method is proposed in this paper for detecting microwave low frequency RFI signals. Only three original variables, one RFI index （sensitive to RFI signal） and two scattering indices （sensitive to snow scattering）, are included in the vector for principal component analysis in this modified method instead of the nine or seven RFI index original variables used in a normal PCA algorithm. The principal component with higher correlation and contribution to the original RFI index is the RFI-related principal component. In the absence of a reliable validation data set of the ＂true＂ RFI, the consistency in the identified RFI distribution obtained from this method compared to other independent methods, such as the spectral difference method, the normalized PCA method, and the double PCA method, give confidence to the RFI signals＇ identification over land. The simple and reliable modified PCA method could successfully detect RFI not only in summer but also in winter AMSR-E data.

关键词： microwave remote sensing radio-frequencyinterference (RFI) the Advanced Microwave ScanningRadiometer for Earth Observing System (AMSR-E),principal component analysis (PCA)

Source analysis of spaceborne microwave radiometer interference over land

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Frontiers of Earth Science 2016年第1期10卷 135-144页

作者： li guan Sibo ZHANG Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration Nanjing University of Information Science & Technology Nanjing 210044 China

Satellite microwave thermal emissions mixed with signals from active sensors are referred to as radio- frequency interference （RFI）. Based on Advanced Micro- wave Scanning Radiometer-Earth Observing System （AMSR-E） observations from June 1 to 16, 2011, RFI over Europe was identified and analyzed using the modified principal component analysis algorithm in this paper. The X band AMSR-E measurements in England and Italy are mostly affected by the stable, persistent, active microwave transmitters on the surface, while the RFI source of other European countries is the interference of the reflected geostationary TV satellite downlink signals to the measurements of spacebome microwave radiometers. The locations and intensities of the RFI induced by the geostationary TV and communication satellites changed with time within the observed period. The observations of spacebome microwave radiometers in ascending portions of orbits are usually interfered with over European land, while no RFI was detected in descending passes. The RFI locations and intensities from the reflection of downlink radiation are highly dependent upon the relative geometry between the geostationary satellite and the measuring passive sensor. Only these fields of view of a spaceborne instrument whose scan azimuths are close to the azimuth relative to the geostationary satellite are likely to be affected by RFI.

关键词： AMSR-E RFI geostationary TV satellite

Preliminary Study on Direct Assimilation of Cloud-affected Satellite Microwave Brightness Temperatures

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Advances in Atmospheric Sciences 2017年第2期34卷 199-208页

作者： Sibo ZHANG li guan Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological AdministrationNanjing University of Information Science and TechnologyNanjing 210044China

Direct assimilation of cloud-affected microwave brightness temperatures from AMSU-A into the GSI three-dimensional variational （3D-Var） assimilation system is preliminarily studied in this paper. A combination of cloud microphysics param- eters retrieved by the 1D-Var algorithm （including vertical profiles of cloud liquid water content, ice water content, and rain water content） and atmospheric state parameters from objective analysis fields of an NWP model are used as background fields. Three cloud microphysics parameters （cloud liquid water content, ice water content, and rain water content） are ap- plied to the control variable. Typhoon Halong （2014） is selected as an example. The results show that direct assimilation of cloud-affected AMSU-A observations can effectively adjust the structure of large-scale temperature, humidity and wind anal- ysis fields due to the assimilation of more AMSU-A observations in typhoon cloudy areas, especially typhoon spiral cloud belts. These adjustments, with temperatures increasing and humidities decreasing in the movement direction of the typhoon, bring the forecasted typhoon moving direction closer to its real path. The assimilation of cloud-affected satellite microwave brightness temperatures can provide better analysis fields that are more similar to the actual situation. Furthermore, typhoon prediction accuracy is improved using these assimilation analysis fields as the initial forecast fields in NWP models.

关键词： atmospheric sounding microwave remote sensing data assimilation cloudy radiances GSI

Effects of humic acid coatings on phenanthrene sorption to black carbon

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Journal of Environmental Sciences 2007年第10期19卷 1189-1192页

作者： WU Cheng ZHANG Xiao-li li guan-bin School of Chemistry and Chemical Engineering Shandong University Jinan 250100 China Shandong Agro-Environment Protection Station Jinan 250100 China

Black carbon （BC） can strongly adsorb hydrophobic organic compounds （HOCs）. The HOC sorption to coated BC could be attenuated in soil and sediment compared with that of the parent BC. To study the potential causes of the sorption attenuation, humic acid （HA） and BC were isolated. Phenanthrene （PHE） was selected as the representative of HOCs. BC was coated with the precipitated HA. The PHE sorption to the HA-coated BC was determined. The HA coatings on BC could result in the significant sorption attenuation of PHE to BC. The attenuation varied in different HA origin and was positively correlated to the aromaticity of HA. The attenuation could be explained by the direct competition between HA and PHE for the available sorption sites on BC and the reduction of the available sorption sites as a result of the pore blockage of BC caused by the HA coatings. Therefore, the HA coatings on BC was one potential cause of the attenuation of HOC sorption to BC in soil and sediment.

关键词： black carbon humic acid phenanthrene sorption attenuation

Trailing (L5) Neptune Trojans: 2004 KV18 and 2008 LC18

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Research in Astronomy and Astrophysics 2012年第11期12卷 1549-1562页

作者： Pu guan li-Yong Zhou Jian li Department of Astronomy & Key Laboratory of Modem Astronomy and Astrophysics in Ministryof Education Nanjing University Nanjing 210093 China

The population of Neptune Trojans is believed to be bigger than that of Jupiter Trojans and that of asteroids in the main belt, although only eight members of this distant asteroid swarm have been observed up to now. Six leading Neptune Trojans around the Lagrange point L4 discovered earlier have been studied in detail, but two trailing ones found recently around the L5 point, 2004 KV18 and 2008 LC18, have not yet been investigated. We report our investigations on the dynamical behaviors of these two new Neptune Trojans. Our calculations show that the asteroid 2004 KV18 is a temporary Neptune Trojan. Most probably, it was captured into the trailing Trojan cloud no earlier than 2.03 ×105 yr ago, and it will not maintain this position later than 1.65 × 105 yr in the future. Based on the statistics from our orbital simulations, we ar- gue that this object is more like a scattered Kuiper belt object. By contrast, the orbit of 2008 LC18 is much more stable. Among the clone orbits spreading within the orbital uncertainties, a considerable portion of clones may survive on the L5 tadpole orbits for 4 Gyr. The strong dependence of the stability on the semimajor axis and resonant angle suggests that further observations are badly required to constrain the orbit in the stable region. We also discuss the implications of the existence and dynamics of these two trailing Trojans over the history of the solar system.

关键词： solar system general -- Kuiper belt -- asteroids -- methods numerical

Application research of narrow band Internet of things buoy and surface hydrodynamics monitoring

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Acta Oceanologica Sinica 2021年第8期40卷 176-181页

作者： Yiqun Xu Jia Wang li guan School of Marine Engineering Jimei UniversityXiamen 361021China Fujian Key Laboratory of Ship and Ocean Engineering Xiamen 361021China

This paper applies the narrow band Internet of things communication technology to develop a wireless network equipment and communication system, which can quickly set up a network with a radius of 100 km on water surface. A disposable micro buoy based on narrow-band Internet of things and Beidou positioning function is also developed and used to collect surface hydrodynamic data online. In addition, a web-based public service platform is designed for the analysis and visualization of the data collected by buoys. Combined with the satellite remote sensing data, the study carries a series of marine experiments and studies such as sediment deposition tracking and garbage floating tracking.

关键词： narrow band Internet of things abandoned buoy hydrodynamics ocean monitoring satellite remote sensing image

One-Dimensional Variational Retrieval of Temperature and Humidity Profiles from the FY4A GIIRS

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Advances in Atmospheric Sciences 2022年第3期39卷 471-486页

作者： Qiumeng XUE li guan Xiaoning SHI Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological AdministrationNanjing University of Information Science and TechnologyNanjing 210044China Department of Mathematics University of Wisconsin-MadisonMadison 53706USA

A physical retrieval approach based on the one-dimensional variational(1 D-Var) algorithm is applied in this paper to simultaneously retrieve atmospheric temperature and humidity profiles under both clear-sky and partly cloudy conditions from FY-4 A GIIRS(geostationary interferometric infrared sounder) observations. Radiosonde observations from upper-air stations in China and level-2 operational products from the Chinese National Satellite Meteorological Center(NSMC)during the periods from December 2019 to January 2020(winter) and from July 2020 to August 2020(summer) are used to validate the accuracies of the retrieved temperature and humidity profiles. Comparing the 1 D-Var-retrieved profiles to radiosonde data, the accuracy of the temperature retrievals at each vertical level of the troposphere is characterized by a root mean square error(RMSE) within 2 K, except for at the bottom level of the atmosphere under clear conditions. The RMSE increases slightly for the higher atmospheric layers, owing to the lack of temperature sounding channels *** partly cloudy conditions, the temperature at each vertical level can be obtained, while the level-2 operational products obtain values only at altitudes above the cloud top. In addition, the accuracy of the retrieved temperature profiles is greatly improved compared with the accuracies of the operational products. For the humidity retrievals, the mean RMSEs in the troposphere in winter and summer are both within 2 g kg^(–1). Moreover, the retrievals performed better compared with the ERA5 reanalysis data between 800 h Pa and 300 h Pa both in summer and winter in terms of RMSE.

关键词： temperature and humidity profiles one-dimensional variational(1D-Var) GIIRS hyperspectral data

Time analysis of regional structure of large-scale particle using an interactive visual system

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Visual Informatics 2022年第2期6卷 14-24页

作者： Yihan Zhang guan li Guihua Shan Computer Network Information Center Chinese Academy of SciencesChina University of Chinese Academy of Sciences China

N-body numerical simulation is an important tool in *** used this method to simulate the formation of structure of the universe,which is key to understanding how the universe *** research on this subject further develops,astronomers require a more precise method that enables expansion of the simulation and an increase in the number of simulation ***,retaining all temporal information is infeasible due to a lack of computer *** the circumstances,astronomers reserve temporal data at intervals,merging rough and baffling animations of universal *** this study,we propose a deep-learning-assisted interpolation application to analyze the structure formation of the ***,we evaluate the feasibility of applying interpolation to generate an animation of the universal evolution through an ***,we demonstrate the superiority of deep convolutional neural network(DCNN)method by comparing its quality and performance with the actual results together with the results generated by other popular interpolation *** addition,we present PRSVis,an interactive visual analytics system that supports global volume rendering,local area magnification,and temporal animation *** allows users to visualize a global volume rendering,interactively select one cubic region from the rendering and intelligently produce a time-series animation of the high-resolution region using the deep-learning-assisted *** summary,we propose an interactive visual system,integrated with the DCNN interpolation method that is validated through experiments,to help scientists easily understand the evolution of the particle region structure.

关键词： Visual analytics Frame interpolation Interactive Particle region structure

Experimental Investigation of Bubble Behaviors in Subcooled Flow Boiling

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Journal of Thermal Science 2012年第2期21卷 184-188页

作者： Peng guan li Jia liaofei Yin Shuo Wang Department of Power Engineering School of Mechanical and Electronic Control Engineering Beijing Jiaotong Univer-sity Shangyuancun No.3 100044 Beijing China

The experimental investigation on vapor bubble growth is performed for analyzing subcooled boiling in a vertical annular channel with inner heating surface and upward water flow under atmospheric pressure. Bulk liquid mass flux ranges from 79 kg/m2s to 316 kg/m2s, and subcooling is from 40 K to 60 K. The bubble behaviors from inception to collapse are captured by High-speed photography. The performance of bubble growth recorded by the high-speed photography is given in this paper. The bubble behaviors, effect of the bubble slippage on the heat transfer, and various forces acting on the bubble are discussed.

关键词： subcooled boiling annular channel bubble behaviors visualization