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101.
李超 《成都信息工程学院学报》1992,(4)
本文通过对1963、1976年两次ELNino事件的分析指出:两次ELNino事件在很多方面较为一致,其主要差别是ELNino开始的地理位置(主要是经度位置)和海温分布不同。同时,又分析了两类不同型式的ELNino年对我国干旱、雨涝和登陆台风的影响。 相似文献
102.
TEQC?????DOS?????????????????TEQC????????????????????????????????????????????????????м??????????????????????????????????????????????????????Visual Basic.NET??TEQC????Windows????????????????????????????????????????????????????????????????????????? 相似文献
103.
基于栅格数据的流域降雨径流模型 总被引:30,自引:0,他引:30
本文在研究降雨时空分布不均匀与下垫面自然地理参数空间分布不均匀,对降雨径流过程影响的基础上,提出了一种在地理信息系统支持下的动态分布式降雨径流流域模型,实现了基于栅格的坡面产汇流与河道汇流的数值模拟,能够获得流域上任意模拟时刻任意栅格的径流量。模型视栅格为水文一致性单元,水文参数在栅格内一致,在相邻栅格间变化,采用Holtan模型计算下渗率,水量平衡方程和线性水库的马斯京根法进行栅格产汇流演算,模 相似文献
104.
105.
Formation and failure of volcanic debris dams in the Chakachatna River valley associated with eruptions of the Spurr volcanic complex, Alaska 总被引:1,自引:0,他引:1
Christopher F. Waythomas 《Geomorphology》2001,39(3-4)
The formation of lahars and a debris avalanche during Holocene eruptions of the Spurr volcanic complex in south-central Alaska have led to the development of volcanic debris dams in the Chakachatna River valley. Debris dams composed of lahar and debris-avalanche deposits formed at least five times in the last 8000–10,000 years and most recently during eruptions of Crater Peak vent in 1953 and 1992. Water impounded by a large debris avalanche of early Holocene (?) age may have destabilized an upstream glacier-dammed lake causing a catastrophic flood on the Chakachatna River. A large alluvial fan just downstream of the debris-avalanche deposit is strewn with boulders and blocks and is probably the deposit generated by this flood. Application of a physically based dam-break model yields estimates of peak discharge (Qp) attained during failure of the debris-avalanche dam in the range 104<Qp<106 m3 s−1 for plausible breach erosion rates of 10–100 m h−1. Smaller, short-lived, lahar dams that formed during historical eruptions in 1953, and 1992, impounded smaller lakes in the upper Chakachatna River valley and peak flows attained during failure of these volcanic debris dams were in the range 103<Qp<104 m3 s−1 for plausible breach erosion rates.Volcanic debris dams have formed at other volcanoes in the Cook Inlet region, Aleutian arc, and Wrangell Mountains but apparently did not fail rapidly or result in large or catastrophic outflows. Steep valley topography and frequent eruptions at volcanoes in this region make for significant hazards associated with the formation and failure of volcanic debris dams. 相似文献
106.
赵靖舟 《地球科学与环境学报》1987,(4)
地球灾变一向被看成是生物进化的破坏性因素,但本文认为,正是这些灾变给生物进化带来一片生机。每一次灾变使旧有生物成批衰亡,往往有几十上百种生物一起灭绝,但同时也使新兴生物的崛起和繁盛有了广阔的生态空间。不仅如此,灾变还可以使旧生物跃变形成新生物,甚至可以制造、创造新生命。生命形成的一系列化合合成反应所需要的巨大能量,恰恰可能来源于形成灾变的火山作用、宇宙射线照射作用等。 相似文献
107.
Glaciers are one of the most important land covers in alpine regions and especially sensitive to global climate change. Remote sensing has proved to be the best method of investigating the extent of glacial variations in remote mountainous areas. Using Landsat thematic mapping (TM) and multi-spectral-scanner (MSS) images from Mt. Qomolangma (Everest) National Nature Preserve (QNNP), central high Himalayas for 1976, 1988 and 2006, we derived glacial extent for these three periods. A combination of object-oriented image interpretation methods, expert knowledge rules and field surveys were employed. Results showed that (1) the glacial area in 2006 was 2710.17 ± 0.011 km2 (about 7.41% of the whole study area), and located mainly to the south and between 4700 m to 6800 m above sea level; (2) from 1976 to 2006, glaciers reduced by 501.91 ± 0.035 km2 and glacial lakes expanded by 36.88 ± 0.035 km2; the rate of glacier retreat was higher in sub-basins on the southern slopes (16.79%) of the Himalayas than on the northern slopes (14.40%); most glaciers retreated, and mainly occurred at an elevation of 4700–6400 m, and the estimated upper limit of the retreat zone is between 6600 m and 6700 m; (3) increase in temperature and decrease in precipitation over the study period are the key factors driving retreat. 相似文献
108.
气候变化对中国木本植物物候的可能影响 总被引:76,自引:1,他引:76
本文根据我国的30年的物候资料和气候资料的统计分析,论证了气温是影响中国木本植物物候的主要因子,在此基础上建立了物候与年平均气温的线性统计模式,又利用此模式分析计算了未来全球年平均气温升高0.5-2.0℃和未来大气中CO2浓度倍增而增暖情况下,我国主要木本植物物候期的大致变幅。 相似文献
109.
都市农业是城市化进程中崭新的农业形态,但缺乏对其组织形式和生产方式的实证研究。本文基于对互润(国际)食品集团的调查实例,详细分析了都市农业加工型企业的成长机理,指出制度平台、政府行为和社区沟通是企业发展的外层机理,是企业平稳运行的基础;生产经营活动及其不断的扩张构成了企业发展的内层机理;创新和企业管理及市场的内、外部控制所形成的内核机理是企业发展的核心动力。据此,文章总结了都市农业加工型企业的发展模式,并就都市农业加工型企业如何发展提出了建议。 相似文献
110.
Yoshihiro Hiramatsu Masataka Ando Tameshige Tsukuda & Tooru Ooida 《Geophysical Journal International》1998,135(3):801-816
Shear-wave splitting from local deep earthquakes is investigated to clarify the volume and the location of two anisotropic bodies in the mantle wedge beneath central Honshu, Japan. We observe a spatial variation in splitting parameters depending on the combination of sources and receivers, nearly N–S fast in the northern region, nearly E–W fast in the southern region and small time delays in the eastern region. Using forward modelling, two models with 30 and 10 per cent anisotropy are tested by means of a global search for the locations of anisotropic bodies with various volumes. The optimum model is obtained for 30 per cent anisotropy, which means a 5 per cent velocity difference between fast and slow polarized waves. The northern anisotropic body has a volume of 1.00° (longitude) × 0.5° (latitude) × 75 km (depth), with the orientation of the symmetry axis being N20°E. The southern anisotropic body has a volume of 1.25° × 1.25° × 100 km with the symmetry axis along N95°E. Our results show that the anisotropic bodies are located in low-velocity and low- Q regions of the mantle. This, together with petrological data and the location of volcanoes in the arc, suggests that the possible cause of the anisotropy is the preferred alignment of cracks filled with melt. 相似文献