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71.
72.
塔里木沙漠公路沿线的起沙风与输沙强度 总被引:19,自引:12,他引:19
塔里木沙漠公路绝大部分路段穿越流沙地段,风沙活动十分强烈,因此,机械防沙带的设置显得十分关键。由于起沙风的统计分析和输沙强度的定量计算是防沙工程设计中的最主要依据之一。该文在大量统计起沙风和野外实地观测的基础上,进行输沙强度的数值计算及分析后指出:由沙漠边缘向内部深入,起沙风更加东偏,输沙强度更大和更为集中。 相似文献
73.
10~30d延伸期天气预报方法研究进展与展望 总被引:2,自引:0,他引:2
Yang Qiuming 《地球科学进展》2015,30(9):970-984
10~30 d延伸期预报是国际大气科学关注的研究热点。这一时间段的预报对开展防灾、救灾工作具有极其重要的价值和意义,该工作需要结合初始气象条件、海洋、大气以及气候的影响因素,其中观测资料具有复杂性、综合性、全球性等,这些科学大数据反映和表征着复杂的自然现象与关系,具有高度数据相关性和多重数据属性,预测过程十分复杂。分析了延伸期预报的各种主流方法,其中重点介绍了动力模式、经典统计和大数据方法 3类预报方法的研究现状,并探讨了各种方法的优势和不足,在此基础上对目前延伸期预报领域存在的问题进行了讨论和总结。对延伸期预报方法的未来发展方向和应用前景给以展望。 相似文献
74.
生态旅游产生于全球人类面临生存的环境危机与人们环境意识的觉醒背景之下.生态旅游的热潮已经来临。为了了解国外生态旅游研究的状况并借鉴其经验.以Science Direct外文数据库作为数据来源,选取1997。2008年137篇论文作为统计研究的数据样本.分别从生态旅游研究的时序特征、研究者背景、成果发表、研究内容和区域等方面分析了国外近十年生态旅游研究发展的基本状况。研究表明:近十年来此领域的研究处于一个发展较快的时期.并存在明显的多学科性和综合性.所涉及案例大都是严格的生态旅游或深度生态旅游.发达国家和发展中国家在生态旅游发展的模式和动力存在较大差异,论文以综述评论和调查型居多。与国外对比显示:我国的研究在跨学科性、研究内容、实证研究、对社区的关注等方面均存在较大差异。 相似文献
75.
76.
Earthquake-induced ground failures in Italy 总被引:8,自引:0,他引:8
The National Catalog of Ground Failures Induced by Strong Earthquakes in Italy (CEDIT), is described. The catalog holds data on ground failures triggered by the earthquakes that occurred in Italy in the last millennium and which had a nominal epicentral intensity equal to or greater than VIII in the Mercalli–Cancani–Sieberg (MCS) intensity scale. The ground effects reported in the catalog are the following: landslides, fractures, liquefaction, surface faulting, and topographic changes of the ground level (subsidence, settlements, tilting, and so on). Each effect is described in terms of seismological parameters of the triggering earthquake, site coordinates and administrative code, lithology and kinematic type of the ground failure. The catalog represents a tool to assess the susceptibility of geologic materials to ground shaking, and to validate predictive models of seismically induced ground displacements (scenarios of earthquake-induced geologic risks). In the context of this study, a simple statistical analysis of the database yielded useful relations between the parameters of the triggering earthquakes and the related effects. 相似文献
77.
78.
Comparing single beam and multibeam echo sounder data where surveys overlap we find that: 95% of multibeam measurements are
repeatable to within 0.47% of depth; older single beam data can be at least as accurate as multibeam; single beam and multibeam
profiles show excellent agreement at full-wavelengths longer than 4 km; archival sounding errors are not Gaussian; 95% of
archival soundings in the northwest Atlantic are accurate to within 1.6% of depth; the 95th percentile error is about five
times greater in pre-1969 data than in post-1968 data; many of the largest errors are located over large seafloor slopes,
where small navigation errors can lead to large depth errors. Our uncertainty model has the form σ
2 = a
2 + (bz)2 + (cs)2, where 2σ is approximately the 95th percentile error, z is the depth, s is the slope, and a, b, c are constants we determine separately for pre-1969 and post-1968 data. 相似文献
79.
上海浦东机场平流雾的统计和监测分析 总被引:6,自引:1,他引:6
利用2000-2009年常规地面观测资料、探空资料和上海浦东机场地面气象例行观测资料,对浦东机场平流雾的气候特征和天气形势背景进行了统计分析.结果发现:浦东机场平流雾发生频次逐年增多、持续时间有增长趋势.从季节分布来看,平流雾多集中在冬春季出现.平流雾天气多发于“入海高压后部”、“副高西北侧”、“低槽气旋”、“台风外围”和“高压前部”等五类特定天气形势背景下.天气系统在空间上的特定配置使暖湿气流得以稳定的流经浦东机场,是浦东机场平流雾形成的根本原因.此外,利用浦东机场2007-2009年自动气象观测系统时间分辨率为1 min的能见度探测资料,对能见度低于200 m的平流浓雾进行分析,结果表明:浓雾爆发不是一次性完成的,稳定的浓雾形成之前会有较长时间的能见度大幅振荡过程,在能见度图谱上形成明显的“象鼻形”先期振荡特征,这一特性也给平流浓雾的监测和预警提供了依据. 相似文献
80.
Edgar L Andreas Reginald J. Hill James R. Gosz Douglas I. Moore William D. Otto Achanta D. Sarma 《Boundary-Layer Meteorology》1998,86(3):379-408
Refuge has patchy vegetation in sandy soil. During midday and at night, the surface sources and sinks for heat and moisture may thus be different. Although the Sevilleta is broad and level, its metre-scale heterogeneity could therefore violate an assumption on which Monin-Obukhov similarity theory (MOST) relies. To test the applicability of MOST in such a setting, we measured the standard deviations of vertical (w) and longitudinal velocity (u), temperature (t), and humidity (q), the temperature-humidity covariance (¯tq), and the temperature skewness (St). Dividing the former five quantities by the appropriate flux scales (u*, *, and q*) yielded the nondimensional statistics w/u*, u/u*, t/|t*|, q/|q*|, and ¯tq/t*q*. w/u*, t/|t*|, and St have magnitudes and variations with stability similar to those reported in the literature and, thus, seem to obey MOST. Though u/u* is often presumed not to obey MOST, our u/u* data also agree with MOST scaling arguments. While q/|q*| has the same dependence on stability as t/|t*|, its magnitude is 28% larger. When we ignore ¯tq/t*q* values measured during sunrise and sunset transitions – when MOST is not expected to apply – this statistic has essentially the same magnitude and stability dependence as (t/t*)2. In a flow that truly obeys MOST, (t/t*)2, (q/q*)2, and ¯tq/t*q* should all have the same functional form. That (q/q*)2 differs from the other two suggests that the Sevilleta has an interesting surface not compatible with MOST. The sources of humidity reflect the patchiness while, despite the patchiness, the sources of heat seem uniformly distributed. 相似文献