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231.
Study of spatial distribution of sandy desertification in North China in recent 10 years 总被引:2,自引:0,他引:2
Sandy desertification is a land degradation characterized by wind erosion, mainly resulted from the excessive human activities in arid, semiarid and part of sub-humid regions in North China. It is one of main kinds of desertification/land degradation as well as water-soil erosion and salinization in China. Rapid and continuous spread of sandy desertification during last 50 years has created a major environmental and socio-economic problem in North China. Remote sensing monitored results in 2000 showed that the sandy desertified land area has been 38.57×104 km2. The area of potential to slightly sandy desertified land is 13.93×104 km2, moderately land 9.977×104 km2, severely land 7.909×104 km2 and very severely land 6.756×104km2. Sandy desertification mainly occurs in the semi-arid mixed farming-grazing zone and its northern rangeland zone, semi-arid dryland rainfed cropping zone and arid oasis-desert margin zone. The average annually developmental rate of sandy desertified land increased from 2,100tion in North China is "overall deterioration, while local rehabilitation". Already achieved rehabilitation results and monitoring assessment show that about 60% of desertified land in North China can be restored under the conditions of rational land-use ways and intensity. 相似文献
232.
Tang Rongchang Qian Hong Huang Zuzhi Wen Dehua Wu Xianguo Cai Changxing Tian Hong Seismological Bureau of Sichuan Province Chengdu China 《中国地震研究》1994,(4)
Based on fault geometric features,composite pattern,faulting land-forms and seismic data,this paper discussed the activity behavior along the northern segment of the Anninghe fault(from Xichang to Shimian)since the Late Pleistocene.The fault can be divided into three active segments by discrepancies of their activity:the segment from Xichang to Mianning,the segment from Mianning to Zimakua,and the segment from Zimakua to Tianwan.The southern segment has the background of occurrence of great earthquakes,but the middle and the northern segments can generate strong and moderate events respectively.According to the features of quartz from fault gouges by scanning electron microscopy(SEM),this paper discussed the movement features along the fault and indicated the stick-slipping feature on the segment from Xichang to Zimakua,the creeping feature on the segment from Jiziping to Tianwan and the transitional feature on the segment in between. 相似文献
233.
近百年来ENSO 强度的变化特征 总被引:1,自引:0,他引:1
利用美国NOAA 提供的月平均海表温度资料和英国Hadley 中心提供的全球逐月海温格点资料,研究了1900-2015 年间厄尔尼诺- 南方涛动现象(ENSO)的强度变化。结果发现,1900-2015 年中ENSO 事件强度发生了明显变化:20 世纪初期至50 年代ENSO 强度为近百年来最弱时期,而从50 年代以后其强度显著增强,特别是70 年代至90 年代末期ENSO 强度达到近百年来最强,但在2000 年以后其强度又有所减弱。进一步分析表明,在20 世纪20-50 年代的强度偏弱期,ENSO 空间型的南北宽度为近百年来最窄,伴随着最大海温异常中心位置偏西;相比之下,在20 世纪70年代以来的强度偏强期,ENSO 空间型的南北宽度达到最宽,对应着最大海温异常中心位置偏东,而2000 年以后的情形有向相反方向发展的趋势。 相似文献
234.
Coincidence of abandoned settlements and climate change in the Xinjiang oases zone during the last 2000 years 总被引:1,自引:0,他引:1
The study on the relationship of abandoned settlements and climate change in the oases could provide a historical reference for understanding human responses to present and future global warming in the arid zone. A total of 554 abandoned historical settlements in Xinjiang Uygur Autonomous Region, China, were used to examine the relationship between abandoned settlements and temperature change over the past 2000 years. The analysis covered dynastic epochs from the Han Dynasty (206BC–220AD) to the Qing Dynasty (1644AD–1911AD) in the oases of Xinjiang. Greater density of settlements was found at the oases larger than 2000 km2, which were more stable and less sensitive to climate change compared to smaller oases. Settlements flourished at small oases and the middle and lower reaches of rivers during warm periods and shrank back to piedmont basins and upstream alluvial fans during cold periods. These results demonstrated responses of oasis agriculture to climate change. 相似文献
235.
The branching of the Tsushima Warm Current (TWC) along the Japanese coast is studied based upon intensive ADCP and CTD measurements
conducted off the Wakasa Bay in every early summer of 1995–1998, the analysis of the temperature distribution at 100 m depth
and the tracks of the surface drifters (Ishii and Michida, 1996; Lee et al., 1997). The first branch of TWC (FBTWC) exists throughout the year. It starts from the eastern channel of the Tsushima Straits,
flows along the isobath shallower than 200 m along the Japanese coast and flows out through the Tsugaru Strait. The current
flowing through the western channel of the Tsushima Straits feeds the second branch of TWC (SBTWC) which develops from spring
to fall. The development of SBTWC propagates from the Tsushima Straits to Noto Peninsula at a speed of about 7 cm sec−1 following the continental shelf break with a strong baroclinicity. However, SBTWC cannot be always found around the shelf
break because its path is influenced by the development of eddies. It is concluded that SBTWC is a topographically steered
current; a current steered by the continental shelf break. Salient features at intermediate depth are the southwestward subsurface
counter current (SWSCC) between 150 m and 300 m depths over the shelf region in 1995–1998 with the velocity exceeding about
5 cm sec−1, although discrepancies of the velocity and its location are observed between the ADCP data and the geostrophic currents.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
236.
广州城市旅游形象定位和建设研究 总被引:6,自引:0,他引:6
根据国内外旅游形象设计发展趋势,提出城市旅游形象设计应有3个层次:(1)城市旅游整体形象;(2)城市旅游特色形象;(3)旅游企业形象。根据Jansen-Varbeke都市旅游产品的界定模式,结合广州实际分析了广州的旅游吸引物,将广州具有国内外吸引魅力的旅游形象定位为:(1)商都旅游,包括购物、美食、商务旅游区作为广州市形象旅游区,并就选址、景点建设提出了初步的构想。 相似文献
237.
2000年来我国人类活动与环境适应以及科学启示 总被引:26,自引:8,他引:18
2000年来人与环境适应是IGBP组织针对全球变化研究进展提出的最新研究方向,实现这一研究方向,中国具有最大的优势。文章针对中国2000年来人类活动的特征,论述了人与环境适应研究的科学框架,并指出由于人类自身对环境变化的感知能力与能动性反应,人类调整生产与生活方式的每一个行动,都可以作为人地互动信息的反映,成为深入认识地球系统长期持续利用与全球变化趋势的依据。 相似文献
238.
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