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Yi G.,CAS Chengdu Institute of Mountain Hazards and Environment | Yi G.,Chengdu University of Technology | Zhang T.,Chengdu University of Technology | Zhang T.,Key Laboratory of Geoscience Spatial Information Technology
International Journal of Environmental Research and Public Health | Year: 2015

The Tibetan Plateau is a key area for research on global environmental changes. During the past 50 years, the climate in the Siling Co lake area has become continuously warmer and wetter, which may have further caused the increase in Siling Co lake area. Based on the Siling Co lake area (2003 to 2013) and climate data acquired from the Xainza and Baingoin meteorological stations (covering 1966 to 2013), we analyzed the delayed responses of lake area changes to climate changes through grey relational analysis. The following results were obtained: (1) The Siling Co lake area exhibited a rapid expansion trend from 2003 to 2013. The lake area increased to 2318 km2, with a growth ratio of 14.6% and an annual growth rate of 26.84 km2·year−1; (2) The rate of air temperature increase was different in the different seasons. The rate in the cold season was about 0.41 °C per ten years and 0.32 °C in hot season. Precipitation evidently increased, with a change rate of 17.70 mm per ten years in the hot season and a slight increase with a change rate of 2.36 mm per ten years in the cold season. Pan evaporation exhibited evidently decreasing trends in both the hot and cold seasons, with rates of −33.35 and −14.84 mm per ten years, respectively; (3) An evident delayed response of lake area change to climate change is observed, with a delay time of approximately one to two years. © 2015 by the authors; licensee MDPI, Basel, Switzerland. Source


Yi G.-H.,CAS Chengdu Institute of Mountain Hazards and Environment | Yi G.-H.,Chengdu University of Technology | Deng W.,CAS Chengdu Institute of Mountain Hazards and Environment | Li A.-N.,CAS Chengdu Institute of Mountain Hazards and Environment | And 2 more authors.
Journal of Mountain Science | Year: 2015

Changes in the lake areas of Xainza basin in the past 33 years (1976 to 2008) were studied using Landsat data from Multispectral Scanners (1973–1977), Thematic Mapper (1989–1992, 2007–2009), and Enhanced Thematic Mapper Plus (1999–2002). The results indicated that lakes in the study area evidently expanded from 1976 to 2008, with total expansion of 1512.64 km2. The mean annual air temperature presented an upward trend with certain fluctuations from 1966 to 2008. The air temperature rise rates in the cold season (0.31°C/10a) were higher than those in the hot season (0.24°C/10a), in the Xainza station example. Precipitation exhibited evident seasonal differences. Mean annual precipitation in hot season is 281.48 mm and cold season is 32.66 mm from 1966 to 2008 in study area. Precipitation in the hot season was the major contributor to the increase in annual precipitation. Grey relational analysis (GRA) was used to study the response of lake areas to climatic factors. The mean air temperature and precipitation were selected as compared series, and the lake areas were regarded as the reference series. The grey relational grade (GRG) between compared series and reference series were calculated through GRA. The results indicated that changes in lake areas were mainly affected by climatic factors in the hot season. Lakes in this region were classified into three grades, namely, Grades I, II, and III according to the recharge source and elevation. The GRGs of each series varied for different grade lakes: the area of Grade III lakes were the most relevant to the hot season factors, the GRGs of precipitation and air temperature were 0.7570 and 0.6606; followed by the Grade II lakes; Grade I lakes were more sensitive to the air temperature. © 2015, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg. Source


Li G.,Sichuan Third Surveying and Mapping Engineering Institute | Ying G.,Sichuan Third Surveying and Mapping Engineering Institute | Wen X.,Sichuan Third Surveying and Mapping Engineering Institute | Chen J.,Sichuan Third Surveying and Mapping Engineering Institute | And 2 more authors.
International Conference on Geoinformatics | Year: 2013

WorldView-2 image data is an important data source for general survey project of geographic national conditions in China. In this research, eight methods, namely Brovey, Ehlers, HPF, HIS, PCA, Wavelet, Pan-Sharpen and Gram-Schimdt were adopted to fuse panchromatic and multi-spectral images of WorldView-2. Qualitative analysis from the aspects of clarity, texture and tone, and quantitative evaluation from the aspects of standard deviation, information entropy, average gradient, deviation index, correlation coefficients, and spectral distortion degree had been done. The results show that the image distortion degree based on the transformation method of Pan-Sharpen is smaller, and meanwhile, the fused image can largely keep the spatial texture details of high-resolution panchromatic band, so it is a suitable method for fusion of WorldView-2 images. © 2013 IEEE. Source


Yi G.-H.,Geomathematics Key Laboratory of Sichuan Province | Yi G.-H.,CAS Chengdu Institute of Mountain Hazards and Environment | Ni S.J.,Chengdu University of Technology | Zhang T.-B.,Geomathematics Key Laboratory of Sichuan Province | And 3 more authors.
Journal of Chengdu University of Technology (Science and Technology Edition) | Year: 2015

This paper discusses the improvement of the system core theory used in the evaluation of geochemical anomalies. Three parameters of the system network graph are provided, including connectivity, connectivity coefficient and stability coefficient, to judge the overall stability of the system network graph and improve the stability evaluation method for the theory of system core. The method is used to analyzes the geochemical anomaly results of the Wulonggou gold deposit zone in Qinghai Province. In 29 combination anomalies (bands) of the region, 25 combination anomalies (bands) with gold prospecting potential have been screened. Among them, in 17 combination anomalies (bands), there are known gold deposits, and the coincident rate reaches 68%. Source


Xian W.,Chengdu University of Information Technology | Xiang Z.,Key Laboratory of Geoscience Spatial Information Technology | Liu L.,Key Laboratory of Geoscience Spatial Information Technology | Shao H.,Key Laboratory of Geoscience Spatial Information Technology
Environmental and Engineering Geoscience | Year: 2015

Zoige County, China, represents a fragile sub-alpine rangeland eco-environment with a severe land desertification problem. This paper aims at detecting land desertification change in Zoige County over 15 years with quantitative remote-sensing techniques using multi-spectral imagery. Landsat images acquired in 1994 and 2009 were analyzed using the following methodology: (1) image pre-processing; (2) spectral mixture analysis (SMA) to obtain precise sub-pixel classification results of land cover; and (3) change vector analysis (CVA) to conduct a multi-temporal comparison process. Change detection results depict the land desertification conditions and vegetation re-growth conditions. In this way, we characterized the spatialtemporal change pattern of land desertification in Zoige County between 1994 and 2009. After categorizing ecological regions based on change detection results, we analyzed the driving factors of both land desertification conditions and vegetation re-growth conditions, finding out that grasslands under intense grazing pressure tend to suffer severe desertification, while topographic relief has an obvious influence on vegetation re-growth. Specific suggestions for each ecological region are proposed, which can assist the development of environmental restoration measures and environmental protection measures in Zoige County in an effective way. Furthermore, this methodology for monitoring land desertification could be carried out across neighboring counties or in other regions with similar sub-alpine rangeland and land desertification problems. Source

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