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Preliminary validation of SMOS sea surface salinity measurements in the South China Sea

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Chinese Journal of Oceanology and Limnology 2015年第1期33卷 262-271页

作者：任永政董庆贺明霞 Key Laboratory of digital earth Science Institute of Remote Sensing and Digital EarthChinese Academy of Sciences Ocean remote sensing institute Ocean University of China

The SMOS(soil moisture and ocean salinity) mission undertaken by the European Space Agency(ESA) has provided sea surface salinity(SSS) measurements at global scale since *** of SSS values retrieved from SMOS data has been done globally and ***,the accuracy of SSS measurements by SMOS in the China seas has not been examined in *** this study,we compared retrieved SSS values from SMOS data with in situ measurements from a South China Sea(SCS) expedition during autumn *** comparison shows that the retrieved SSS values using ascending pass data have much better agreement with in situ measurements than the result derived from descending pass *** in terms of bias and root mean square error(RMS) of the SSS retrieved using three different sea surface roughness models is very consistent,regardless of ascending or descending *** ascending and descending measurements are combined for comparison,the retrieved SSS using a semi-empirical model shows the best agreement with in situ measurements,with bias-0.33 practical salinity units and RMS *** also investigated the impact of environmental conditions of sea surface wind and sea surface temperature on accuracy of the retrieved *** SCS is a semi-closed basin where radio frequencies transmitted from the mainland strongly interfere with SMOS ***,accuracy of retrieved SSS shows a relationship with distance between the validation sites and land.

关键词： sea surface salinity (SSS) soil moisture and ocean salinity (SMOS) sea surface roughnessmodel South China Sea (SCS)

Spatial Exploration of Multiple Cropping Efficiency in China Based on Time Series remote sensing Data and Econometric Model

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Journal of Integrative Agriculture 2013年第5期12卷 903-913页

作者： ZUO Li-jun WANG Xiao LIU Fang YI Ling institute of remote sensing and digital earth Chinese Academy of Sciences

This study explored spatial explicit multiple cropping efficiency （MCE） of China in 2005 by coupling time series remote sensing data with an econometric model - stochastic frontier analysis （SFA）. We firstly extracted multiple cropping index （MCI） on the basis of the close relationship between crop phenologies and moderate-resolution imaging spectroradiometer （MODIS） enhanced vegetation index （EVI） value. Then, SFA model was employed to calculate MCE, by considering several indicators of meteorological conditions as inputs of multiple cropping systems and the extracted MCI was the output. The result showed that 46% of the cultivated land in China in 2005 was multiple cropped, including 39% double- cropped land and 7% triple-cropped land. Most of the multiple cropped land was distributed in the south of Great Wall. The total efficiency of multiple cropping in China was 87.61% in 2005. Southwestern China, Ganxin Region, the middle and lower reaches of Yangtze River and Huanghuaihai Plain were the four agricultural zones with the largest rooms for increasing MCI and improving MCE. Fragmental terrain, soil salinization, deficiency of water resources, and loss of labor force were the obstacles for MCE promotion in different zones. The method proposed in this paper is theoretically reliable for MCE extraction, whereas further studies are need to be done to investigate the most proper indicators of meteorological conditions as the inputs of multiple cropping systems.

关键词： multiple cropping efficiency multiple cropping index (MCI) time series of MODIS/EVI stochastic frontieranalysis (SFA) China

Permafrost environment monitoring on the Qinghai-Tibet Plateau using time series ASAR images

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International Journal of digital earth 2015年第10期8卷 840-860页

作者： Zhen Li Panpan Tang Jianmin Zhou Bangsen Tian Quan Chen Sitao Fu Key Laboratory of digital earth Institute of Remote Sensing and Digital EarthChinese Academy of SciencesBeijingChina institute of remote sensing and digital earth University of the Chinese Academy of SciencesBeijingChina

The permafrost in Qinghai-Tibet Plateau(QTP)has long been the focus of many *** this study,we first use the method that integrates synthetic aperture radar(SAR)intensity and phase information to monitor permafrost environment in the Beiluhe Region,using time series advanced SAR *** backscattering coefficients(σ^(0))and deformation were extracted for the main features,and the influences of meteorological conditions to them were also *** results show that both the change inσ^(0)and surface deformation are closely related to the active layer,and the deformation is also affected by the permafrost ***,over meadow and sparse vegetation regions,σ^(0)rose about 6.9 and 4 dB from the freezing to thawing period,respectively,which can be mainly attributed to the thaw of the active layer and increased ***,seasonal deformation,derived from the freeze-thaw cycle of the active layer,was characteristic of frost heave and thaw settlement and exhibited a negative correlation with air *** magnitude was larger than 1 cm in a seasonal ***,significant secular settlement was observed,with rates ranging from-16 to 2 mm/a,and it was primarily due to the thaw of the permafrost table caused by climate warming.

关键词： Qinghai-Tibet Plateau ASAR permafrost environment backscattering coefficients deformation climate warming

Retrieval of sea surface winds under hurricane conditions from GNSS-R observations

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Acta Oceanologica Sinica 2016年第9期35卷 91-97页

作者： JING Cheng YANG Xiaofeng MA Wentao YU Yang DONG Di LI Ziwei XU Cong State Key Laboratory of remote sensing Science Institute of Remote Sensing and Digital EarthChinese Academy of Sciences National Engineering Center for Geoinformatics Institute of Remote Sensing and Digital EarthChinese Academy of Sciences

Reflected signals from global navigation satellite systems（GNSSs） have been widely acknowledged as an important remote sensing tool for retrieving sea surface wind *** power of GNSS reflectometry（GNSS-R）signals can be mapped in delay chips and Doppler frequency space to generate delay Doppler power maps（DDMs）,whose characteristics are related to sea surface roughness and can be used to retrieve wind ***,the bistatic radar cross section（BRCS）,which is strongly related to the sea surface roughness,is extensively used in ***,a bistatic radar cross section（BRCS） map with a modified BRCS equation in a GNSS-R application is *** the BRCS map,three observables are proposed to represent the sea surface roughness to establish a relationship with the sea surface wind *** Hurricane Dennis（2005） GNSS-R data are then *** than 16 000 BRCS maps are generated to establish GMFs of the three ***,the proposed model and classic one-dimensional delay waveform（DW） matching methods are compared,and the proposed model demonstrates a better performance for the high wind speed retrievals.

关键词： global navigation satellite system-reflectometry Hurricane Dennis delay doppler maps bistatic radar cross section map sea surface wind speed

Asymmetrical mirror optimization for a 140 GHz TE_(22,6) quasi-optical mode converter system

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Chinese Physics B 2017年第7期26卷 75-80页

作者：夏冬金铭白明 School of Electronics and Information Engineering Beihang University institute of remote sensing and digital earth State Key Laboratory of remote sensing

We introduce an asymmetrical mirror design to a 140 GHz TE_（22,6） quasi-optical（QO） mode converter system to correct the asymmetry of the beam＇s field distribution caused by the Denisov launcher. By such optimization, the output beam with better symmetrical distribution is obtained at the system＇s output window. Based on the calculated results,the QO mode converter system＇s performance is already satisfying without iterative phase correction. Scalar and vector correlation coefficients between the output beam and the fundamental Gaussian beam are respectively 98.4% and 93.0%,while the total power transmission efficiency of the converter system is 94.4%. The assistance of optical ray tracing to the design of such QO mode converters is introduced and discussed as well.

关键词： asymmetrical mirror design optical ray tracing quasi-optical mode converter

Geospatial technologies for Chang’e-3 and Chang’e-4 lunar rover missions

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Geo-Spatial Information Science 2020年第1期23卷 87-97页

作者： Kaichang Di Zhaoqin Liu Wenhui Wan Man Peng Bin Liu Yexin Wang Sheng Gou Zongyu Yue State Key Laboratory of remote sensing Science Institute of Remote Sensing and Digital EarthChinese Academy of SciencesBeijingChina

This paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover *** mapping techniques were used to produce topographic products of the landing site with meter level resolution using orbital images before landing,and to produce centimeter-resolution topographic products in near real-time after *** positioning techniques were used to determine the locations of the two landers using descent images and orbital basemaps immediately after *** surface operations,visual-positioning-based rover localization was performed routinely at each waypoint using Navcam *** topographic analysis and rover localization results directly supported waypoint-to-waypoint path planning,science target selection and scientific investigations.A GIS-based digital cartography system was also developed to support rover teleoperation.

关键词： Geospatial technology lunar rover landing site mapping topographic analysis rover localization and navigation

An improved constraint method in optimal estimation of CO2 from GOSAT SWIR observations

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Science China earth Sciences 2017年第2期60卷 286-296页

作者： ZOU MingMin CHEN LiangFu LI ShenShen FAN Meng TAO JinHua ZHANG Ying State Key Laboratory of remote sensing Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences Beijing 100101 China

We propose an algorithm that combines a pre-processing step applied to the a priori state vector prior to retrievals, with the modified damped Newton method （MDNM）, to improve convergence. The initial constraint vector pre-processing step updates the initial state vector prior to the retrievals if the algorithm detects that the initial state vector is far from the true state vector in extreme cases where there are CO2 emissions. The MDNM uses the Levenberg-Marquardt parameter ~,, which ensures a positive Hessian matrix, and a scale factor a, which adjusts the step size to optimize the stability of the convergence. While the algorithm iteratively searches for an optimized solution using observed spectral radiances, MDNM adjusts parameters ）, and a to achieve stable convergence. We present simulated retrieval samples to evaluate the performance of our algorithm and comparing it to existing methods. The standard deviation of our retrievals adding random noise was less than 3.8 ppmv. After pre-processing the initial estimate when it was far from the true value, the CO2 retrieval errors in the boundary layers were within 1.2 ppmv. We tested the MDNM algorithm＇s performance using GOSAT Llb data with cloud screening. Our preliminary validations comparing the results to TCCON FTS measurements showed that the average bias was less than 1.8 ppm and the correlation coefficient was approximately 0.88, which was larger than for the GOSAT L2 product.

关键词： Retrieve Optimal estimation CO2 GOSAT

Forest canopy height mapping over China using GLAS and MODIS data

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Science China earth Sciences 2015年第1期58卷 96-105页

作者： YANG Ting WANG Cheng LI GuiCai LUO SheZhou XI XiaoHuan GAO Shuai ZENG HongCheng Key Laboratory of digital earth Science Institute of Remote Sensing and Digital EarthChinese Academy of Sciences University of Chinese Academy of Sciences National Satellite Meteorological Center China Meteorological Administration National Key Laboratory of remote sensing Institute of Remote Sensing and Digital EarthChinese Academy of Sciences Faculty of Forestry University of Toronto

The Geoscience Laser Altimeter System(GLAS)accurately detects the vertical structural information of a target within its laser spot and is a promising system for the inversion of structural features and other biophysical parameters of forest *** the GLAS footprints are discontinuously distributed with a relativity low density,continuous vegetation height distributions cannot be mapped with a high accuracy using GLAS data *** MODIS BRDF product provides more forest structural information than other optical remote sensing *** study aimed to map forest canopy heights over China from the GLAS and MODIS BRDF ***,the waveform characteristic parameters were extracted from the GLAS data by the method of wavelet analysis,and the terrain index was calculated using the ASTER GDEM ***,the model reducing the topographic influence was constructed from the waveform characteristic parameters and terrain ***,the final canopy height estimation model was constructed from the neural network combining the canopy height estimated with the GLAS point and the MODIS BRDF data,and applied to get the continuous canopy height map over ***,the map was validated by the measured data and the airborne Li DAR data,and the validation results indicated that forest canopy heights can be estimated with high accuracy from combined GLAS and MODIS data.

关键词： GLAS waveform decomposition terrain index canopy height model

Mineral abundances and different levels of alteration around Mawrth Vallis,Mars

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Geoscience Frontiers 2015年第5期6卷 741-758页

作者： Sheng Gou Zongyu Yue Kaichang Di Jinnian Wang State Key Laboratory of remote sensing Science.institute of remote sensing and digital earth Chinese Academy of Sciences

Spectral indices from OMEGA hyperspectral data show that there are two main phyllosilicates exposed in and around Mawrth Vallis:Al phyllosilicates and Fe/Mg *** analysis of CRISM spectra shows that Al phyllosilicates such as montmorillonite,hydrated silica,kaolinite;Fe/Mg phyllosilicates such as nontronite,saponite,serpentine are widespread on the light-toned *** similar stratigraphical sequences,morphologies and textures are observed on both sides of Mawrth Vallis from HiRISE images,suggesting that the geological processes that formed these units must have operated at a regional scale;the multiple endmember spectral mixture analysis(MESMA) derived mineral abundance indicates that there is a higher level of alteration in the western side relative to the eastern *** suggest that the observed phyllosilicates,stratigraphical sequences and different levels of alteration might have been caused by sedimentary deposition processes in which the composition of the external source sediment or the local solution was different,or by a pedogenic process closely related to the leaching of abundant liquid water with different chemical properties.

关键词： Spectral analysis MESMA Mineral abundance Alterati