基于GIS的北京市延庆县地质灾害易发性区域划分   总被引：3，自引：0，他引：3  

张有全  宫辉力  李巧刚 《中国地质灾害与防治学报》2006,17(4):17-20,24

随着灾害科学研究的深入，区域地质灾害已成为其重要的研究领域。文章利用遥感技术及GPS工具获取地质灾害的特征信息，在对地质灾害的成因背景分析基础上，运用GIS空间分析功能和地质灾害危险性评价、评估理论构建了地质灾害发育度模型。以北京市延庆县为实验区，采用ArcEngine＆．NET进行易发性分区程序的编写，计算研究区域内单元网格的发育度值。为了克服调查数据的局限性和人为因素，在计算发育度时引入修正系数，从延庆县DEM数据中提取单元格网内的地形坡度值，根据坡度值区间确定修正系数。将发育度计算结果按照一定规律、原则聚类。进行地质灾害易发性区域划分，取得了与实际情况较为一致的结果。基于“3S”技术及灾害地质条件，采用地质灾害发育度模型，可以较好地用于区域地质灾害易发性区域的划分，并能为防灾、减灾提供重要信息。  相似文献   

额济纳旗胡杨根区水分运动参数的确定--利用Richard方程和气象资料推算   总被引：2，自引：0，他引：2  

朱永华  仵彦卿 《水文》2002,22(1):1-3

利用Richard方程和气象资料相结合的办法,确定了中国典型的干旱内陆河流──黑河下游额济纳旗地区主要成林的干旱荒漠天然乔木树种──胡杨林地的水分运动参数,主要有导水系数K、比水容量C和水分扩散率D。  相似文献   

Evaluating Models Of The Neutral, Barotropic Planetary Boundary Layer Using Integral Measures: Part Ii. Modelling Observed Conditions     

G. D. Hess  J. R. Garratt 《Boundary-Layer Meteorology》2002,104(3):359-369

The steady-state, horizontally homogeneous, neutral, barotropiccase forms the foundation of our theoretical understanding of the planetary boundary layer (PBL).While simple analytical models and first-order closure models simulate atmospheric observationsof this case well, more sophisticated models, in general, do not. In this paperwe examine how well three higher-order closure models, E - - l, E - l, and LRR - l,which have been especially modified for PBL applications, perform in predicting the behaviour of thecross-isobaric angle ₀, the geostrophic drag coefficient C_g, and the integral of the dissipationrate over the boundary layer, as a function of the surface Rossby number Ro. For comparison we alsoexamine the performance of three first-order closure mixing-length models, two proposed byA. K. Blackadar and one by H. H. Lettau, and the performance of the standard model forsecond-order closure and a modification of it designed to reduce the overprediction of turbulence inthe upper part of the boundary layer.  相似文献   

Displaced-Beam Small Aperture Scintillometer Test. Part Ii: Cases-99 Stable Boundary-Layer Experiment   总被引：3，自引：3，他引：0  

O. K. Hartogensis  H. A. R. De Bruin  B. J. H. Van De Wiel 《Boundary-Layer Meteorology》2002,105(1):149-176

The performance of the Scintec displaced-beam small aperture scintillometer (DBSAS) in the stable boundary layer (SBL) is investigated using data gathered during the CASES-99 experiment in Kansas, U.S.A. The DBSAS is superior to the eddy-covariance method in determining vertical fluxes of sensible heat and momentumclose to the ground and/or over short (< 1 min) averaging intervals. Both aspects are of importance in the shallow and non-stationary SBL.The friction velocity, u_*, the temperature scale, _*, and from these the sensible heat flux, H, were calculated from the indirectly determined dissipation rate, , and the structure parameter of temperature, C_T ², by the DBSAS, which was operated over a path length of 112 m. All these variables are compared with eddy-covariance data for 10-minute time averages. Previously reported systematic errors in the DBSAS, overestimation of u_* for low u_* values and underestimation of u_* for high u_* values, have in part been dealt with by adjusting the beam displacement distance from 2.7 mm to 2.6 mm in the calculations. The latter adjustment is presented as a working hypothesis, not a general solution.  相似文献   

Using a Large-Aperture Scintillometer to Measure Absorption and Refractive Index Fluctuations     

J. P. Nieveen  A. E. Green  W. Kohsiek 《Boundary-Layer Meteorology》1998,87(1):101-116

The contributions of refraction and absorption fluctuations to the measured scintillations are observed for a near-infrared absorption region using a NOAA designed large-aperture scintillometer. The logarithmic amplitude spectra are shown to decay with frequency as f^-8/3 for both the absorption and scattering mechanisms. For the absorption mechanism this is in line with similar observations made at microwave and infrared frequencies. However, for finite transmitting and receiving apertures, theory predicts a stronger decay of the scattering mechanism due to aperture averaging. The spectral shape is characterised by a region of low frequency absorption, higher frequency refraction and separated by a flattish transition zone. The upper observed corner frequency (f_C2) compares well with values calculated using the measured transverse windspeed (v) for a known aperture radius. The lower corner frequency (f_C1) position is shown to be sensitive to the ratio of the real and imaginary part of the refractive index structure parameter, (C _nR ² /C _nI ² )^3/8, and v. The part of the spectrum associated with the absorption scintillations is observed to be much less than that due to refraction through the day until evening, when decreasing C _nR ² causes C _nR ² /C _nI ² to decrease and absorption to become significant. If absorption is ignored, this may have consequences for calculating nocturnal surface fluxes. During unstable, daytime conditions the large aperture scintillometer is most sensitive to refractive scintillations despite having an infrared source transmitting in a lossy atmosphere. But also under these conditions, the low frequency absorption part of the spectrum is observable.  相似文献   

1991年夏东亚阻塞高压形成的诊断分析   总被引：20，自引：6，他引：14  

王亚非  宋永加 《气象学报》1998,56(2):212-224

文中将１９９１年夏季在东亚地区发生的阻塞高压分为发展期,旺盛期及衰亡期等３个阶段进行了细致的诊断分析。发现在东亚阻塞高压的第一、二阶段其上游有明显的波活动通量与２～６ｄ尺度的Ｅ矢量通量传播。即定常罗斯贝波的传播与天气尺度扰动的共同作用有利于东亚阻塞高压的维持。第一阶段西风气流的分支处有比第二阶段更为明显的南北向分布的涡动位势涡度的辐散辐合偶极子说明了天气尺度扰动给阻塞高压的发展提供了很重要的能源,显然天气尺度扰动在阻塞高压的发展阶段起着比旺盛阶段更为显著的作用。本文还注意到乌拉尔阻塞高压的崩溃与东亚阻塞高压形成的某些联系。  相似文献   

雹云的3参数概率判别法   总被引：4，自引：0，他引：4  

杨传凤  陈秀杰  黄秀韶  袁希强 《气象》1998,24(9):36-40

根据山东省雷达回波资料,天气和灾情实况,统计了回波顶高Ｈｍ强回波区顶高Ｈｚ回波强度Ｚ与降雹概率的关系,给出单,双参数判别雹云的指标,提出用３参数降雹条件概率法判别雹云,指出了３参数识别指标对降雹的预示作用,这对强对流天气的短期预报具有一定的实用价值。  相似文献   

强降水雷达回波参数特征     

杨梅 《气象》1998,24(6):32-35

利用７１３型测雷达资料,对江西强降水回波参数特征进行统计,分析结果表明：强降水与回波顶高、回波强度、水平尺度及地形等有关,为强降水天气预测提供了依据．  相似文献   

不同下垫面的大气边界层湍流扩散特征          下载免费PDF全文

赵志强  郑乃廷 《应用气象学报》1998,9(4):478-484

利用海洋、戈壁、城郊和城市4种不同下垫面上的湍流观测资料,运用多尺度湍流概念和方法计算分析了风速谱和扩散参数等湍流特征量。结果表明:下垫面的粗糙度对大气边界层湍流特征影响很大,随着粗糙度的增大,速度谱的峰值频率向高频方向移动,扩散参数增大。  相似文献   

GS—15型重力仪滤波效能与观测稳定性的对比分析     

杨又陵  蔚晓利 《内陆地震》1998,12(3):215-221

通过观察和模拟干扰源试验,认为红山地震台ＧＳ－１５型重力仪潮汐观测曲线畸变和观测精度氏是因原配ＲＣ滤波电路的抗干扰能力差。用自制的有源贝赛尔滤波电路取代原配ＲＣ滤波电路后,观测质量得到了根本的改善,一系列参量的分析表明,ＧＳ型重力仪弹性系统手换能电路性能优良,有源滤波电路具有很强的抗干扰能力,使用数字记录代替模拟记录可以减小记录系统非线性失真,提高潮汐分析的精度和稳定性。  相似文献