专题要素分级的新方法及其应用   总被引：3，自引：2，他引：3  

孙亚梅  王如云 《测绘学报》1994,23(1):59-66

本文是Ｊｅｎｋｓ和Ｃａｓｐａｌｌ工作的基础上，提出了一个量度分级总体精度的统计量，它不仅可以反映各个等级内部数值的紧密程度，而且可以反映各个等级之间的相差程度。这为专题要素的合理分级提供了一种更为客观可靠的方法。  相似文献   

中国自然灾害的空间分布特征   总被引：11，自引：1，他引：11  

王铮  张丕远 《地理学报》1995,50(3):248-255

中国自然灾害的分布以秦岭－淮河线、胡焕庸线以及青藏高原外缘为界，可划分为四个大区，即北域、南域、西域和过滤带亚域。以灾害的单位面积失论，黄淮海地区是我国重点灾区，另一个重点区位于川、滇、黔、桂交界地段，它以人员的伤亡而突出。如果以灾害发生的总经济损定义灾害规模，则活动的规模中心位于以洞庭－武汉和郑州为两端点的地区。  相似文献   

A numerical experiment on the general circulation of the middle atmosphere with a three-dimensional model explicitly representing internal gravity waves and their breaking     

Hideji Kida 《Pure and Applied Geophysics》1984,122(5):731-746

The general circulation of the middle atmosphere is simulated by means of a three-dimensional primitive equation model which covers from the south pole to the north pole but is limited to a ten-degree sector in the latitudinal direction; cyclic conditions are imposed at the east—west lateral boundaries. The model is capable of explicitly representing internal gravity waves of zonal wavelength greater than a few hundred kilometers with the use of a one-degree mesh, but planetary-scale waves were excluded. No parameterization is employed for subgrid-scale eddy viscosity (or diffusivity).With the assumption of a simple external-heating function corresponding to solstice conditions, a time integration was performed for about thirty days from the motionless state. During the whole period, random forcings were imposed on each grid of the lowest level in order to generate small-scale upwardly propagating internal gravity waves.The experiment has shown that small-scale waves were indeed excited, propagated upward, broke up near the mesopause, and greatly changed the thermally induced zonal mean motion and temperature fields in the upper mesosphere and lower thermosphere. As a result, important features of the general circulation at those levels, such as reversals of the zonal motion and the latitudinal gradient of zonal mean temperature were reproduced.  相似文献   

云南省5月份雨量的天气气候成因探讨   总被引：24，自引：1，他引：24       下载免费PDF全文

严华生  琚建华 《应用气象学报》1995,6(1):124-128

该文探讨了影响云南5月雨量的大气环流背景、天气气候成因，指出大气环流季节性转换、ITCZ、南亚高压、西太平洋副高等是大气环流背景;夏季风和西风槽相互作用、北方冷空气与南方暖湿气流相互作用是天气气候成因。以此为预报思路，得出一个云南5月雨量长期预报模式。  相似文献   

基于GIS的小流域水土流失遥感定量监测研究   总被引：14，自引：1，他引：14  

刘耀林  罗志军 《武汉大学学报(信息科学版)》2006,31(1):35-38

以三峡库区典型小流域为研究区域，通过遥感和野外调查进行信息采集．建立了流域环境数据库；在GIS支持下，根据修正通用土壤流失方程（RUSLE）模型对数据库实施运算操作，探讨了流域内土壤侵蚀强度的空间分布规律，并估算了小流域水土流失量。  相似文献   

地震企业停减产损失评估     

林均岐  钟江荣  申选召 《世界地震工程》2006,22(4):18-21

对在地震间接经济损失中占主要的停减产损失的定义进行了讨论,对目前的研究现状进行了总结和回顾,对现有评估方法进行了讨论,结合地震现场的工作性质和特点,给出了现场评估的建议方法。  相似文献   

Overview of Taiwan Earthquake Loss Estimation System   总被引：2，自引：1，他引：2  

Chin-Hsun Yeh  Chin-Hsiung Loh  Keh-Chyuan Tsai 《Natural Hazards》2006,37(1-2):23-37

The National Science Council (NSC) of Taiwan started the HAZ-Taiwan project in 1998 to promote researches on seismic hazard analysis, structural damage assessment, and socio-economic loss estimation. The associated application software, “Taiwan Earthquake Loss Estimation System (TELES)”, integrates various inventory data and analysis modules to fulfill three objectives. First, it helps to obtain reliable estimates of seismic hazards and losses soon after occurrence of large earthquakes. Second, it helps to simulate earthquake scenarios and to provide useful estimates for local governments or public services to propose their seismic disaster mitigation plans. Third, it helps to provide catastrophic risk management tools, such as proposing the seismic insurance policy for residential buildings. This paper focuses on the development and application of analysis modules used in early loss estimation system. These modules include assessments of ground motion intensity, soil liquefaction potential, building damage and casualty.  相似文献   

Long-term biogeochemical cycling in agroecosystems inferred from C, C and N     

B.H. Ellert  H.H. Janzen 《Journal of Geochemical Exploration》2006,88(1-3):198

We investigated C and N cycling in long-term agroecological experiments initiated over 50 years ago at a cool, semi-arid site on the North American Great Plains. We used isotopes at natural abundance to trace C and N exchange between soils and plants in contrasting cropping systems. Both ¹³C and ¹⁴C indicated that the soil organic matter was isotopically distinct from current plant inputs, suggesting that recently added plant C was cycling independently of much of the soil C pool. For tracing recent C flows, bomb-¹⁴C was more sensitive than ¹³C, and increased more in high – than in low – yielding systems. Analysis of ¹⁵N in plant tissues, as an index of ¹⁵N in actively cycling soil N, suggested that biological and industrial N fixation both tended to decrease plant ¹⁵N, whereas livestock manure addition increased ¹⁵N abundance. Collectively, the data suggest that soil organic matter is kinetically heterogeneous, so that a majority of soil C and N inputs and outputs exchange with only the small pool of soil organic matter that is actively cycling. Consequently, recently photosynthesized C and deposited N may not readily enter the old, stable fractions of soil organic matter. Practices to retain CO₂ from the atmosphere and prevent leakage of reactive N to non-agricultural systems should therefore focus on management of this active pool.  相似文献   

中耕对紫色土坡耕地产流产沙影响     

傅斌王玉宽  王先拓王勇强朱波  王道杰 《山地学报》2006,24(B10):77-81

四川盆地紫色土地区有除草中耕的习惯。研究中耕对产流产沙的影响对于指导坡耕地管理和水土保持建设具有重要意义。在野外小区开展了人工模拟降雨试验，结果表明：（1）中耕能够增加水分入渗，在19．61mm／h雨强下，可以提高稳渗率2．97％到36．56％，在53．95mm／h下，可以提高稳渗率9．74％到90．46％，在111．69mm／h雨强下，能提高稳渗率12．47％到54．1％；（2）中耕可以减少坡面产流，在缓坡、中等雨强条件下，中耕峰值流量仅相当于对照的30％，而在陡坡、大雨强下，二者的峰值流量十分接近；（3）在小雨和中雨条件下，中耕减少侵蚀产沙，在暴雨条件下的中耕会导致产沙量增加。  相似文献   

新疆近53年洪灾研究   总被引：2，自引：0，他引：2  

王秋香  任宜勇  张静  刘静 《沙漠与绿洲气象(新疆气象)》2006,29(6):1-3

用新疆近53a洪灾资料筛选出的814例资料,对洪灾进行等级划分,共分为特级、一级、二级、三级共四级,以此为根据,分析各级洪灾时空分布规律。研究表明,阿克苏、喀什和昌吉地区是新疆各级洪灾次数最多的地方,是重洪灾区。阿勒泰、塔城、博州、伊犁和南疆的巴州是次重洪灾区。夏季是各级洪灾的多发季节,春季洪灾主要集中在损失较小的一、二、三级。从1987年开始,由于新疆气候趋暖、夏季降水显著增多,而且超标准洪水变率明显增强,洪灾次数增多,量值增大。  相似文献