检索结果-南通市图书馆

A LAI Inversion Algorithm Based on Directional Reflectance

在线全文

学校读者我要写书评

暂无评论

A LAI Inversion Algorithm Based on Directional Reflectance

Numerical study of successive CMEs during November 4―5, 1998

中国气象学会2.04年年会

作者： Tang Shihao~(12. (1 National satellite Meteorological center,{2. Meteorological Administration, beijing 100081,{2. 2.Remote Sensing and GIS Research center, Department of Geography, beijing Normal University, beijing 100875,{2.)

＜正＞Leaf area index (LAD is an important ecological and environmental parameter. The current remote sensing inversion methods of leaf area index can mainly（?）e grouped into two classes: vegetation index based methods and remote sensing physical model based methods. In this paper, a new LAI retrieval method is developed. The algorithm borrows ideas from the principles and methods of ground LAI measurements, and adopts a new frame which differs from traditional remote sensing LAI inversion methods. First, the relationship between LAI and directional gap fraction is derived from the definition of LAI. Then, directional gap fraction is acquired from remote sensing bidirectional reflectance distribution function （BRDF） product. This acquisition is obtained by the use of a kernel driven model and a large scale directional gap fraction algorithm. At last, the large scale LAI is calculated through angle integrations. This algorithm has been applied to get LAI distribution of china in the middle of July, 2.02. The ground data acquired from two field experiments conducted in Changbai Mountain and Qiiian Mountain, china, are used to validate the algorithm. In order to resolve the scale change problem between high resolution grouad observation and low resolution remote sensing data, two high resolution remote sensing images almost ha, ing the same resolutions with ground measurements are used as transitions. In order to proceed, we first bulid an empirical relationship between measured LAI and high resolution reflectance. Then, we get high resolu ion LAI distribution according to that relation. The LAI value of a low resolution pixel is calculated from the areal weighted sum of high resolution LAIs composing the low resolution pixel. Our results show that the algo（?）ithm has a high precision. Factors that may influence the precision of the algorithm are also discussed in this paper.

关键词： LAI MODIS BRDF ALBEDO Gap fraction

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2008年第10期51卷 1600-1610页

作者： ZHOU YuFen & FENG XueShang SIGMA Weather Group, State Key Laboratory for Space Weather, center for Space Science and Applied Research, Chinese Academy of Sciences, beijing 100190,{2. SIGMA Weather Group State Key Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences

We present the solar-terrestrial transit process of three successive coronal mass ejections (CMEs) of November 4―5, 1998 originating from active region 8375 by using a time-dependent three-dimensional magnetohydrodynamics (MHD) simula-tion. These CMEs interacted with each other while they were propagating in inter-planetary space and finally formed a "complex ejecta". A newly developed SIP-CESE MHD model was applied to solve MHD equations numerically. The quiet solar wind was started from Parker-like 1D solar wind solution and the magnetic field map was calculated from the solar photospheric magnetic field data. In our simulation, the ejections were initiated using pulse in the real active region 8375. The interplanetary disturbance parameters, such as speed, direction and angular size of the expanding CME, were determined from the SOHO/LASCO data with the cone-model. We discussed the three-dimensional aspects of the propagation, in-teraction and merging of the three ejections. The simulated interplanetary shocks were compared with the nearby-Earth measurement. The results showed that our simulation could reproduce and explain some of the general features observed by {2. for the "complex ejecta".

关键词： complex ejecta three-dimensional MHD simulation SIP-CESE MHD model

A Novel Network Management Model Based on XML for Service and resource

在线全文

学校读者我要写书评

暂无评论

计算机工程 2002年第S1期28卷 77-81页

作者： ZHANG JinxiangWU JianpingWANG Jilong(Network Research center of Tsinghua University, beijing 100084,{2., jxzhang@***) Network Research center of Tsinghua University Beijing 100084China j xzhang ***

XML can allow for the interchange of data between management applications using different information models. Furthermore, CORBA technique is increasingly used in the management of service and {2. in the heterogeneous network environment. As the scheme of information arrangement of CORBA is flat file style, which handles querying, deleting, and insertinginformation inefficiently, this paper puts forward a novel network management model based on XML in the domain of the management of CERNET (china Education and Research Network), which has used a tree structure of managed objects arrangement to provide efficient operation on managed objects. In addition, arrangement, definition, implementation and finding schemes for CORBA managed objects using XML are also given by the tree structure, and thus can arrange and retrieve managed objects efficiently.

关键词： XMLCORBANetwork managementModel

A Spectral Index for Estimating Soil Salinity in the Yellow River Delta Region of china Using EO-1 Hyperion data

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Pedosphere 2010年第3期20卷 378-388页

作者： WENG Yong-Ling GONG Peng ZHU Zhi-Liang Department of Surveying and Mapping Engineering College of Transportation Southeast University Nanjing 210096(China) State Key Laboratory of Remote Sensing Science Institute of Remote Sensing Applications of the Chinese Academy ofSciences and Beijing Normal University Beijing 100101 (China) Department of Environment Science Policy and Management University of California Berkeley CA 94720 (USA) EROS data center U.S. Geological Survey Sioux Falls SD 57198 (USA)

Soil salinization is one of the most common land degradation processes. In this study, spectral measurements of saline soil samples collected from the Yellow River Delta region of china were conducted in laboratory and hyperspectral data were acquired from an EO-1 Hyperion sensor to quantitatively map soil salinity in the region. A soil salinity spectral index (SSI) was constructed from continuum-removed reflectance (CR-reflectance) at 2.52.and 2.03 nm, to analyze the spectral absorption features of the salt-affected soils. There existed a strong correlation (r = 0.91) between the SSI and soil salt content (SSC). Then, a model for estimation of SSC with SSI was established using univariate regression and validation of the model yielded a root mean square error (RMSE) of 0.986 and an R2.of 0.873. The model was applied to a Hyperion reflectance image on a pixel-by-pixel basis and the resulting quantitative salinity map was validated successfully with RMSE = 1.92. and R2.= 0.62.. These suggested that the {2. hyperspectral data had the potential for predicting SSC in a large area.

关键词： hyperspectral reflectance soil salt content spectral absorption features

Process and mechanism of arable land change in Hebei Province during the past 50 years

在线全文

学校读者我要写书评

暂无评论

Journal of Geographical Sciences 2001年第4期11卷 47-52页

作者： XU Yue-qing (Institute of Geographical Sciences and Natural resources Research, CAS, beijing 100101,{2. College of resource and Environment Science, Hebei Normal University, Shijiazhuang 050016,{2. )

Hebei Province is one of the regions with most densely population, fastest economic growth and most intensive land use in china. The contradiction of land shortage sharpened by high-speed economic development with population growth has become a serious problem, which has restricted regional sustainable *** paper revealed the basic process, regional differences of change and the gravity center of arable land area according to the long-series statistical {2. of arable land during the past 50 years. On the basis of the above mentioned, the major driving forces that influence the changes of the arable land are discussed. The research results indicate that there is a trend of obvious fluctuating decrease in arable land area during the last 50 years. The changes of arable land area undergo the process from increase to sharp decrease to gently decrease. The regional disparity of change in arable land area is very notable and the gravity center of arable land area moves to the northeast 49.2. km. Regarding the decrease in arable land, the direct driving forces include adjustments of agricultural structure and reclamation, and indirect driving forces include advance in technology, economic interest and population growth etc.

关键词： decrease in arable land area changing process mechanism Hebei Province

Role of surface evaporation in surface rainfall processes

在线全文

学校读者我要写书评

暂无评论

Role of surface evaporation in surface rainfall processes

Atmospheric frontal gravity waves observed in satellite SAR images of the Bohai Sea and Huanghai Sea

“2.10年北京气象学会中青年优秀论文评选”学术研讨会

作者： Xiaopeng Cui and Xiaofan Li 1 Laboratory of Cloud-Precipitation Physics and Severe Storms,Institute of Atmospheric Physics,Chinese Academy of Sciences,beijing,china. 2.Joint {2. for satellite data Assimilation and National Oceanic and Atmospheric Administration/National Environmental satellite,data,and Information Service {2. for satellite applications and Research,Camp Springs,Maryland,USA.

The roles of surface evaporation in tropical surface rainfall processes in rainfall regions(raining stratiform and convective regions) and rainfall-free regions(nonraining stratiform and clear-sky regions) are investigated on the basis of the data from a series of two-dimensional cloud-resolving *** model is integrated for 2. days with imposed zonally uniform vertical velocity,zonal wind,horizontal temperature,and vapor advection,as well as sea surface temperature from the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment(TOGA COARE).The model is also integrated to equilibrium states for 40 days with imposed zero vertical velocity,constant zonal wind,and sea surface temperatures of 31℃and 2.℃for two separate *** time- and zonal-mean surface evaporation mainly comes from rainfall-free regions,where the surface evaporation is largely balanced by the vapor divergence associated with the *** rainfall regions the vapor convergence determines the convective rainfall while the surface evaporation plays a negligible role. Thus surface evaporation pumps water vapor into rainfall-free regions,and the divergence transports the vapor from rainfall-free regions to rainfall regions,which supports the *** forcing and sea surface temperature do not change the role of surface evaporation in rainfall processes.

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2010年第5期29卷 35-43页

作者： LIU Shuming LI Ziwei YANG Xiaofeng Pichel William G YU Yang ZHENG Quanan LI Xiaofeng The First Institute of Oceanography State Oceanic Administration Qingdao 266061 China National Marine data and Information Service Tianjin 300171 China Institute of Remote Sensing applications Chinese Academy of Science Beijing 100101 China NOAA/NESDIS Center for Satellite Applications and Research Camp Springs MD 20746-4304 USA Department of Atmospheric and Oceanic Science University of Maryland Maryland 20742-2425 USA IMSG at NOAA/NESDIS NOAA E/RA3 WWBG Room 102 5200 Auth Road Camp Springs MD 20746-4304 USA.

In the satellite synthetic aperture radar（SAR） images of the Bohai Sea and Huanghai Sea,the authors observe sea surface imprints of wave-like patterns with an average wavelength of 3.8 *** SAR observations with sea surface wind fields and surface weather maps,the authors find that the occurrence of the wave-like phenomena is associated with the passing of atmospheric *** authors define the waves as atmospheric frontal gravity *** dynamical parameters of the wave packets are derived from statistics of 9 satellite SAR images obtained from 2.02.to 2.08.A two-dimensional linear physical wave model is used to analyze the generation mechanism of the *** atmospheric frontal wave induced wind variation across the frontal wave packet is compared with wind retrievals from the SAR *** CMOD-5（C-band scatterometer ocean geophysical model function） is used for SAR wind retrievals VV（transmitted vertical and received vertical） for ENVISAT and HH（transmitted horizontally and received horizontally） for RADARSAT-1.A reasonable agreement between the analytical solution and the SAR observation is *** new SAR frontal wave observation adds to the school of SAR observations of sea surface imprints of AGWs including island lee waves,coastal lee waves,and upstream Atmospheric Gravity Waves（AGW）.

关键词： Atmospheric gravity waves atmospheric front generation mechanism synthetic aperture radar

Application of DEM overlaying technique in surface subsidence identification─a case study in Ruqigou coal mining area of Ningxia,china

在线全文

学校读者我要写书评

暂无评论

Journal of Geographical Sciences 1999年第1期9卷 43-50页

作者： CHEN Li-ding(Research center for Eco-Environmental Sciences, Chinese Academy of Sciences,beijing 100085,{2.)

Subsidence occurred in many parts of the world. particularly in densely populated deltaic regions, causing extremely expensive damage. It can be resulted from natural causes. man-made induced causes, or other mixed causes. For identifying surface subsidence, many techniques have been employed, for example, geodetic monitoring, airborne laser subsidence measurement system,differential S.A.R., interferometry DGPS, and satellite radar measurements. However. all these methods require large time span and a large amount of field work. With the development of GIS techniques, identification of surface subsidence is becoming a relative easy problem. Ruqigou coal mining area was selected as a case study to identify the surface subsidence with DEM (digital elevation model) overlaying techniques. The result shows that DEM overlaying technique is a very useful method on surface subsidence identification. The accuracy of the results are largely dependent on the precision of the data-input.

关键词： surface subsidence Rubsidence coal mining area GIS DEM overlaying technique

Duststorms and the Related Disasters

在线全文

学校读者我要写书评

暂无评论

Duststorms and the Related Disasters