山东极端强降水天气环境参数特征

基于2012-2015年期间上海市多次明显强降水过程的逐时110积水报警数据(积水灾情)和气象站降水量数据, 分析降水和积水灾情两者之间的关系和时空动态变化, 建立了上海城市人口密集区强降水积水的阈值指标。结果表明:上海中心城区强降水积水的起始阈值为1 h降水量30 mm, 当中心城区1 h降水量在70 mm以上时, 积水会显著增多。上海区县人口密集居住区强降水的起始阈值为1 h降水量35 mm。降水积水的严重程度不仅与降水强度相关, 也与累积降水量和降水持续时间的长短有关。当2 h累积降水达到40 mm以上时, 也有积水灾情。积水灾情相对于降水有1-2 h左右的滞后期。

     

基于TRMM/PR的长江下游地基雷达一致性订正

不同雷达观测相同目标的反射率因子差异会影响雷达组网应用效果,对无波束阻挡的X波段雷达而言,这种差异主要由雷达定标偏差和信号衰减引起,其中衰减包含降水导致的衰减以及天线罩水膜导致的衰减。为了订正定标偏差、天线罩水膜衰减以及降水衰减,设计了一个基于相控阵雷达组网的订正方法。首先,将天线罩水膜导致的衰减看作定标偏差的一部分,使用组网衰减订正算法做初次衰减订正;然后,通过构建一个雷达网观测偏差函数,使用梯度下降法求解各雷达之间的定标偏差;最后,将订正了定标偏差的原始反射率因子再次使用组网衰减订正算法进行二次衰减订正。对上述订正方法,用于广东省佛山市7部X波段相控阵天气雷达探测的一次冷空气降水过程进行检验。结果显示,传统的PIA (Path-integrated attenuation)算法订正结果与广州S波段天气雷达观测结果相关系数为0.53,均方根误差为9.0 dB, 而该算法这两项数值分别为0.64和8.4 dB,优于PIA;在台风外围的局地强降水过程中也得到了相同的结论。

     

Land-surface segmentation as a method to create strata for spatial sampling and its potential for digital soil mapping

Sampling efforts are constrained by limited availability of resources. Therefore, methods to reduce the number of samples, while still achieving reasonable accuracy are needed. Land-surface segmentation (LSS) has proven a powerful technique to partition digital elevation models (DEMs) and their derivatives into relatively homogeneous areas, which can be further employed as support in soil sampling. Though topography is one of the main soil forming factors, a robust assessment of the potential of this technique to digital soil mapping (DSM) is still missing. In this study, we aimed at evaluating the potential of LSS in stratifying a landscape into relatively homogeneous areas, which can be used as strata for guiding the selection of sampling points in DSM. The experiments were carried out in two study areas where soil samples were available. Land-surface derivatives were derived from DEMs and segmented with a tool based on the multiresolution segmentation algorithm, into objects considered as homogeneous soil-landscape divisions. Thus, one sample was randomly selected within each segment from the existing sample data, based on which predictions of soil classes/sub-orders and properties, i.e. soil texture and A-horizon thickness, were made. Results were compared with predictions based on simple random sampling (SRS) and conditioned Latin hypercube (cLHS). The segmentation-based sampling (SBS) scheme performed better than SRS and cLHS schemes in predicting the A-horizon thickness, soil texture fractions and soil classes, showing a high potential of LSS in stratifying a landscape for the purposes of DSM. The novelty of this study is in the way strata are constructed, rather than in the sampling design itself. Further research is needed to demonstrate the value of a SBS design for practical use. The analyses presented here further highlight the importance of considering locally adaptive techniques in optimization of sampling schemes and predictions of soil properties.     

江西省交通区位演变与区域发展效应

选择江西省作为典型研究区域,采用历史分析与空间分析方法,基于长时间序列研究不同交通运输阶段交通区位的动态演变过程,并对其所引致的区域发展特征进行分析.结论是:在传统交通运输阶段向近代化及现代化交通运输阶段转变过程中,江西省宏观交通区位分别表现为国家南北交通控扼中枢,铁路建设的滞后区与周边发达地区间的交通过境区,可达性演变特征则由南北方向可达性的优势区逐步演化为滞后区.不同时期相对应的区域发展特征表现为,从传统运输阶段的区域商贸全面繁荣,走向近代工业化进程滞后及当前经济发展边缘化.在总结典型案例基础上,尝试从成因层,演变层,作用层,效应层和反馈层五个层面探讨交通区位与区域发展的内在作用关系.     

阿克苏河流域的面雨量序列及其与径流关系

以数字高程模型 (DEM) 的1km×1km网格数据为基础,对阿克苏河流域14个气象站和水文站的1961~2000年的年降水资料进行了自然正交分解 (EOF),通过回归分析,建立主要特征向量与地理因子的插值模型,给出了一个面雨量序列的计算方法,为建立气候要素的区域平均序列提供了一个有效的解决方案,并由此推算出年阿克苏流域平均年降水量的空间分布以及面雨量序列。径流量与面雨量之比 (R/P) 平均为0.43,最高为0.69 (1997年),最低为0.30 (1963年)。计算出的阿克苏河流域面雨量序列与阿克苏河实测径流量序列的趋势变化率分别为5.79×10⁸ m³/10a和4.29×10⁸ m³/10a,两者均表现出增加趋势,但面雨量的增加速率要比径流量大一些,年际变化幅度也要大,面雨量和径流量的变差系数Cv值分别为0.17和0.13。阿克苏河年径流量的变化与夏季0^oC层高度、年面雨量有着十分密切的关系,表明20世纪90年代以来新疆气候的变化是阿克苏河流域径流稳定增加的一个非常重要的因素。     

Re-evaluation of focal depths and source mechanisms of selected earthquakes in the Afar depression

We present a stepwise inversion procedure to assess the focal depth and model earthquake source complexity of seven moderate-sized earthquakes  (6.2 > M _w > 5.1)  that occurred in the Afar depression and the surrounding region. The Afar depression is a region of highly extended and intruded lithosphere, and zones of incipient seafloor spreading. A time-domain inversion of full moment tensor was performed to model direct P and SH waves of teleseismic data. Waveform inversion of the selected events estimated focal depths in the range of 17–22 km, deeper than previously published results. This suggests that the brittle–ductile transition zone beneath parts of the Afar depression extends more than 22 km. The effect of near-source velocity structure on the moment tensor elements was also investigated and was found to respond little to the models considered. Synthetic tests indicate that the size of the estimated, non-physical, non-isotropic source component is rather sensitive to incorrect depth estimation. The dominant double couple part of the moment tensor solutions for most of the events indicates that their occurrence is mainly due to shearing. Parameters associated with source directivity (rupture velocity and azimuth) were also investigated. Re-evaluation of the analysed events shows predominantly normal faulting consistent with the relative plate motions in the region.     

A SIMILARITY MEASURE FOR CHEMICAL DATA: APPLICATIONS TO CLUSTER ANALYSIS

The results of unsupervised pattern recognition methods are critically dependent on the measure ofsimilarity used for clustering objects. There is little a priori information available on the relative utilityof various similarity measures. We introduce here an alternative similarity measure based on the metrictensor measure (MTM). Two standard clustering strategies are tested with the proposed similaritymeasure: hierarchical clustering and the K-median method. As data we use the ARCH obsidian data,a data set on Hungarian coal, and trace element data on Hungarian paprika. Differences from theMahalanobis distance measure are described for intraclass relations.     

非洲投资环境地域差异研究

本文在总结国内外投资环境研究方法的基础上,根据区域特殊性、综合性与可操作性等原则构建了由30项指标组成的指标体系,采用主成分分析的数据处理方法,对非洲各国投资环境进行了综合定量评价,将其分为优（I≥2）、良（1≤I〈2）、差（0．8≤I〈1）和极差（I〈0．8）四大类,以便为我国企业对非投资提供决策参考。     

科尔沁沙地固定沙丘土壤水体积分数变化

利用2006-2009年5-9月科尔沁沙地固定沙丘0~150 cm土壤水体积分数监测数据及降水资料,采用偏度、峰度检验法检验了固定沙丘不同月及不同土层土壤水体积分数的正态性,并得到了其正态分布相关参数的估计值及其置信区间;同时,对不同土层、不同月及不同年间的土壤水体积分数变化和差异进行了分析。结果表明:(1)固定沙丘同一月的土壤水体积分数以显著性水平α=0.1通过正态分布的假设检验;固定沙丘土壤水体积分数的平均值范围1.82%~4.95%,主要集中在2%~4%;(2)受降水影响,固定沙丘7月土壤水体积分数较高,且与其他月的差异显著;7月土壤水体积分数均值和方差的点估计及置信水平为0.95的置信区间、统计特征均与其他月的有较大差异;(3)固定沙丘0~10 cm土壤水体积分数较低,且与其他土层有显著差异;而10~30 cm土壤水体积分数较高;(4)2008年土壤水体积分数较低,而2009年土壤水体积分数较高;除2007年与2008年土壤水体积分数没有显著差异外,其余年份间的土壤水体积分数均有显著差异。