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Li B.,Chinese Academy of Sciences | Su H.,CAS Institute of Geographical Sciences and Natural Resources Research | Chen F.,Chinese Academy of Sciences | Wu J.,Beijing Normal University | Qi J.,Center for Land and Resources
Natural Hazards | Year: 2013

Drought is one of the most detrimental natural disasters. Studying the changing characteristics of drought is obviously of great importance to achieve the sustainable use of water resources at river basin scales. In this paper, the satellite-based Vegetation Condition Index (VCI) and Vegetation Health Index (VH) were firstly calculated by using NDVI and brightness of the Global Vegetation Index dataset derived from Advance Very High Resolution Radiometer for China in growing seasons over 1982-2005. Then, the long-term VCI and VH data were employed to study the variation of droughts in the ten basins covering the whole country. The linear trend of each pixel showed that most parts of China were getting wetter in growing seasons, and the drought areas defined by the number of drought pixels have decreased in most basins. The increasing trend of basin averaged values of VCI and VH also indicates the whole country was generally getting wetter. At last, to better understand the two remote sensing drought indices, the response of the growing-season VCI and VH was compared to that of the Palmer Drought Severity Index and 6-month Standard Precipitation Index. Significant spatial variability of the relationship between the VCI, VH, and the station-based meteorological drought indices was shown, and some more closely related areas were found. The study will be useful for water resources management for each basin in the future. © 2013 Springer Science+Business Media Dordrecht. Source


Liu X.-Y.,Jilin University | Fang H.-B.,Center for Land and Resources
2nd International Conference on Information Science and Engineering, ICISE2010 - Proceedings | Year: 2010

Through analysis of the copper mineralization characteristics in the area of Rigaze region in Tibet, using the weights of evidence method on Rigaze copper mineralization vision to predict areas, establish the copper deposit prospecting model, and extraction of various types and mineralization related to the formation, structure, intrusive rocks, aeromagnetic, geochemical for 14 evidence factor layers. using GIS spatial analysis function, it generated in the study area forming the posterior probability map, which can divided copper deposits vision mineralization areas into A, B two grades by the posteriori probability value. Finally in order to further ore-prospecting laid solid foundation. delineation of the three A-level areas and five B-level areas, for future research to lay a solid foundation for further exploration. © 2010 IEEE. Source


Chen H.,Center for Land and Resources | Chen H.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Zhuang D.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research
2012 1st International Conference on Agro-Geoinformatics, Agro-Geoinformatics 2012 | Year: 2012

Crop plantation map is a fundamental data in the research and production of agriculture. Remote sensing is a fast, economic and irreplaceable tool in this research and application area. By the analysis of the penology of winter wheat and summer maize using the data from agro-meteorological station and the characteristics analysis of the 8-day time-series MODIS NDVI of winter wheat and summer maize, this paper proposed a model to extract the distribution of winter wheat and summer maize based on NDVI apex and valley characters. The threshold of winter wheat at county level in the model was derived with the density cutting method using the agricultural statistical data of planting area and MODIS NDVI data. The relationship between threshold and latitude was proposed, which reflects the controlling role of latitude to temperature and crop growth. Then, the threshold of winter wheat at the pixel level was estimated using the above-mentioned relationship. Using this threshold, we get the distribution of winter wheat. The accuracy evaluation using 90 stations showed that the overall areal resolution is about 91.15% and the accuracy at county scale is averaged as 67.52%. The distribution of summer maize was extracted using the threshold at county level. The distribution map demonstrated that the coverage of winter wheat and summer maize were affected by the growing condition at local region. Most of them appeared at plain, but less of them distributed at the region with bad condition such as rugged and salt-affected seaside area. In the yanshan and taihangshan mountainous area, the land surface is rugged with high slope, thin soil and poor irrigation condition. So, the amount of crops is limited in this area. Otherwise, in the plain area before the mountain area and the lower plain the winter wheat and summer maize were widely planted with percentage more than 60%. Lastly, in the coastal area near bohai gulf which was affected by salt, the crops were rare in distribution. © 2012 IEEE. Source


Chen H.,Center for Land and Resources | Chen H.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Zhuang D.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research
2012 1st International Conference on Agro-Geoinformatics, Agro-Geoinformatics 2012 | Year: 2012

Net primary production (NPP) is an important parameter for the global carbon cycle research, and the remote sensing methods to estimate of it are widely concerned. In this paper, we proposed a modified CASA model to estimate NPP. Firstly, we used a new method to estimate solar radiation based on the relationship between sunset angle and sunshine hour, and then the distribution of solar radiation needed for the regional NPP calculation was acquired. Secondly, we utilized the local parameters of maximum light use efficiency 0.51gC/MJ for winter wheat and 0.66gC/MJ for summer maize specifically. Thirdly, a new water limitation factor based on LSWI (The Land Surface Water Index), which can reflect the irrigation effects, was used. Lastly, a FPAR retrieval strategy based on searching table for MODIS replaced the former CASA method. Using the common meteorological data, 8-day MODIS reflection data (MOD 09) and the distribution map of winter wheat and summer maize at Huang-Huai-Hai plain, the NPP map was acquired using the above parameterized and optimized CASA model. The yearly NPP of winter wheat is 6.028·1013gC, and that of summer maize is 4.132·1013gC at this region. The trend at time and space is clear. Double apex distribution of NPP at temporal scale is shown, the spatial distribution of winter wheat NPP is obviously related with latitude (r0.640). The value of NPP is related with climate. Winter wheat NPP is related with temperature (r0.637) and rainfall (r0.446), but summer maize NPP is most affected by solar radiation (r0.662) and sunshine (r0.614). In the different subregions of the research area, the highest winter wheat NPP (1098.89 gC/m 2a) and summer maize NPP(805.20gC/m2a) both appear in eastern Shandong district, but the lowest average NPP at subregion level is in the coastal area for winter wheat (216.62gC/m2a) and in northern Jiangsu plain for summer maize (482.10gC/m2a). © 2012 IEEE. Source


Zhao H.L.,Center for Land and Resources | Fan J.H.,Center for Land and Resources | Wang R.Y.,China University of Geosciences | Liu G.,CAS Institute of Remote Sensing
IET Conference Publications | Year: 2015

It is quite difficult for the scientists to carry out the field scientific research on mountain glaciers, due to the special geographical position and formidable natural conditions. In addition, the conventional measurement methods are not able to meet the requirements of the rapid monitoring and quantitative evaluation for the glacier changes. As an advanced technique for spatial information acquisition, SAR (Synthetic Aperture Radar) can monitor the ground surface motion with high precision under all weather. The unique advantages indicate that SAR is the optimum method for glacier monitoring. Considering the baseline length, temporal baseline and the continuity, three COSMO images were selected to carry out the study of the glacier flow velocity in the Tianshan Mountains using Offset-Tracking technology. From the result, we can see the displacement of the range direction of Tianshan glacier is relatively obvious while compared to the displacement of the azimuth direction. The velocity of the glacier displacement reduces from glacier axis to both sides, and increases from its origin to snowline and then reduces towards the end. Source

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