M-P分布时降水返回信号估算雨滴谱参数方法

为了能通过简单计算得到雨滴谱参数,在假设雨滴谱分布满足M-P函数的情况下,对降水返回信号估算雨滴谱参数方法进行了研究。通过雷达气象方程、雨滴下降末速度与雨滴直径的关系,得到雷达降水返回信号与雨滴谱参数之间的关系,构成方程组。采用解方程的方法,得到降水返回信号估算雨滴谱参数的解析式。用正演方法建立检验数据库,将估算值与设定值进行误差分析,截距参数的平均相对误差的平均值为0.55%,斜率参数的平均相对误差的平均值为0.84%。研究结果表明,当雨滴谱分布服从M-P函数时,降水返回信号估算雨滴谱参数方法可行。     

NINO区SST与SOI的耦合振荡信号及其预测试验

应用奇异交叉谱（ＳＣＳＡ）分析方法,提取Ｎｉｎｏ 海区各区的平均海温（ＳＳＴ）和南方涛动指数（ＳＯＩ）之间的耦合振荡信号,由此描述其年际和年代际的时变特征。基于ＳＣＳＡ,重建耦合振荡分量序列（ＲＣＣＳ）,并与回归分析相结合,对Ｎｉｎｏ 各海区平均的ＳＳＴ月际序列作短期气候预测试验。结果表明,各海区ＳＳＴ与ＳＯＩ的显著耦合振荡周期各有特色,其年际或１０ 年际变化不尽相同,从而构成了ＥＮＳＯ信号在时空演变型态上的复杂性。ＳＣＳＡ基础上的回归预报模型的预报技巧绝大部分优于ＳＳＡ－ＡＲ预报模型,实际预报试验证明效果优良     

基于MSSA的区域GPS站点季节性信号提取

基于MSSA同时提取多个GPS站点高程时间序列中的季节性信号,主要包括1 a项与0.5 a项。MSSA利用重建成分进行信号重构时,可从原始时间序列中提取有用信号,并剔除干扰噪声。将MSSA与SSA各自获取的前10个奇异谱方差所占百分比和重构信号进行对比,MSSA重构曲线中只包含多个站点的时变与具有共性的季节性信号,有效消除了单个站点特有的噪声与局部现象的影响。     

基于多源、 多时相遥感影像的高原湖泊提取及其不确定性——以西藏羊卓雍错流域为例

基于野外实地考察, 以西藏中南部羊卓雍错流域为例, 探讨了基于多源、 多时相遥感影像的高原湖泊提取. 目前计算机辅助分类方法在高原湖泊提取上存在很大的局限性, 目视解译方法虽然繁琐, 但能结合丰富的经验信息, 故而成为当今高原湖泊提取的较为现实与可行的方法. 为此, 针对各季湖面特征的不同相态, 结合图像增强技术、 DEM等辅助信息和野外实地验证, 建立了高原湖泊不同时相的遥感解译标志. 根据1972-2009年Landsat、 CBERS和HJ-1A/1B等3种不同数据源的37幅遥感影像提取了流域内主要湖泊, 并分析了湖泊面积的年内与年际变化. 在此基础上, 讨论了高原湖泊提取过程的不确定性, 包括遥感影像甄选、 几何校正误差、 数字化容差和目视解译经验等给结果带来的不确定性. 结果表明: 引入高分辨率、 多源遥感影像以及不受天气状况影响的微波影像有助于高原湖泊变化监测能力与解译精度的提高; 而综合考虑地形信息、 湖泊不同时相特征, 适用于多种数据源的计算机自动解译算法研发, 将提高长时间序列高原湖泊提取的效率.     

弱GPS信号捕获算法的仿真实验研究

针对低信噪比环境下导航的需要,文章对低信噪比环境下弱GPS信号捕获算法进行了分析,重点对相关累加、非相关累加以及多重数据位循环相关累加捕获算法的信号处理流程和算法捕获性能进行讨论。通过特定的硬件装置获得真实的GPS信号,利用Matlab对上述3种常用的弱GPS信号捕获算法进行计算机仿真研究。根据理论分析和仿真结果可以看出,多重数据位循环相关捕获算法更适合检测低信噪比环境下的GPS信号。     

Facies and architecture of a tide-dominated segment of the Late Pliocene Orinoco Delta (Morne L'Enfer Formation) SW Trinidad

Exceptionally high shelf-subsidence rates (0.8–6.0+ mm/yr), a marked basinward stepping (to east and northeast) of the paleo-Orinoco shelf prism and post-Pliocene uplift of Trinidad all allow the sedimentary facies, process regime and the evolution of the Late Miocene Orinoco Delta to be evaluated from extensive outcrops along the southwest, and south coasts of Trinidad. The ca. 200 km easterly growth (late Miocene to present) of the Orinoco shelf-margin was generated by repeated cross-shelf, regressive–transgressive transits of the Orinoco Delta system. The studied Late Pliocene segment of this shelf-margin prism allows insight to how this margin was built. The Morne L'Enfer Formation (Late Pliocene) along Cedros Bay and Erin Bay in SW Trinidad, provides a window into the facies and process regime of the ca. 850 m-thick deltaic succession at an inner-shelf location some 100 km landward of the coeval shelf edge. Regressive facies associations include tide-influenced delta-front to prodelta deposits (FA1) within upward coarsening units, shoreface to offshore deposits, possibly with prograding mud cape deposits (FA2), and fluvial distributary channel infills (FA3), as well as muddy sediments of floodbasins and coastal embayments between the distributary channels (FA4), and tide-influenced bay-head delta deposits (FA5). Transgressive facies associations show an overall upward fining of grain size and include inner estuary distributary channels with minimal brackish-water or tidal influence (FA6), transition zone fluvial-tidal distributary channels (FA7), tide-dominated mid-outer estuary channel-bars (FA8), and intertidal to supratidal flat units (FA9). The tidal signals in both deltaic and estuarine units include bi-directional paleocurrents (channels), frequent mud drapes within stacked sets of cross-strata (delta-front), fluid mud layers, flaser, wavy and lenticular bedding, and ubiquitous spring-neap stratal bundling. The tide dominated nature of the paleo-delta in SW Trinidad was likely due to its location within an embayed proto-Columbus Channel, though by analogy with the modern Orinoco Delta, it is predicted that the same succession becomes wave dominated to the east as the delta emerged to the open ocean and approached the outer shelf and shelf-edge region. It is difficult to estimate how much of the abundant mud in the Pliocene deltaic sequences was derived from inner-shelf littoral currents with suspended Amazon River mud. The studied Late Pliocene Morne L'Enfer succession contains some 17 high-frequency transgressive–regressive sequences, each ca. 40–60 m thick, estimated to have an average time duration of 90–120 Ky. By analogy, the last glacial cycle on the Orinoco shelf saw the delta prograding across the 200 km-wide shelf to the shelf edge in ca. 100 Ky, then transgressing back to its present position in 20 Ky. A predicted model of the linkage between the study succession on SW Trinidad and its eastward continuation offshore towards the outer shelf and shelf edge in the Columbus Basin is suggested.     

Data mining methods for hydroclimatic forecasting

Skillful streamflow forecasts at seasonal lead times may be useful to water managers seeking to provide reliable water supplies and maximize hydrosystem benefits. In this study, a class of data mining techniques, known as tree-structured models, is investigated to address the nonlinear dynamics of climate teleconnections and screen promising probabilistic streamflow forecast models for river–reservoir systems. In a case study of the Lower Colorado River system in central Texas, a number of potential predictors are evaluated for forecasting seasonal streamflow, including large-scale climate indices related to the El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), and others. Results show that the tree-structured models can effectively capture the nonlinear features hidden in the data. Skill scores of probabilistic forecasts generated by both classification trees and logistic regression trees indicate that seasonal inflows throughout the system can be predicted with sufficient accuracy to improve water management, especially in the winter and spring seasons in central Texas.     

2016—2019年湖北省气象预警信号的时空分布特征与发布原则

研究气象预警信号发布的时空特征与发布原则,对监测极端灾害性天气和发布预警信号有一定的指示意义.对湖北省2016—2019年期间发布的气象预警信号运用分类统计法按信号类别、等级、发布时间、发布区域进行统计分析,发现暴雨、大风、雷电、大雾、高温为主要的预警信号,预警落区主要分布在鄂东南、鄂西南,预警发生时间主要集中在夏季的7—8月.在此基础上,提出了湖北省气象预警信号的发布原则.     

Use of two-dimensional electric resistivity and ground penetrating radar for archaeological prospecting at the ancient capital of Egypt

Two-dimensional (2-D) resistivity and ground penetrating radar (GPR) surveys facilitate tracing of buried archaeological relics at the archaeological site of the Tell El Rabi'a, southwestern Cairo. These surveys also provide information on variations in depth of the groundwater table, which affect both exhumed and buried archaeological remains. The 2-D electrical resistivity profiles obtained show some high anomalies (up to 6900 Ω m). Based upon on-site calibration at partly exhumed sites, such anomalies are interpreted as pillar crowns and wall-like structures of hard limestone of the Hathour temple. The low background resistivities are interpreted to represent riverine deposits with differing moisture (or saturation) characteristics. The results of the GPR survey show three forms of high-amplitude radar anomalies, denoted as “P, H and R”. The “P” anomalies have semi-hyperbolic shapes, which suggest the presence of thin buried walls. The second, near-horizontal group of anomalies, “H”, may be either due to the presence of thick buried walls or arise from coincidental parallel alignment of survey lines with buried linear structures. The third group of GPR anomalies “R” is composed of chaotic reflections, and interpreted to depict buried stone-filled chambers. Some un-exhumed parts of the study area show weak radar reflections with occasional highly attenuated radar signals. These phenomena are ascribed to differing compaction and moisture characteristics of riverine soil layers. Recommendations with regard to archaeological site-excavation, preservation of archaeological relics, and soil conservation are submitted.     

连续重力观测资料同震信号的一种分离方法

采用正则化平滑因子方法,对重力台站连续观测资料进行处理和讨论,尝试分离同震信号。结果表明,该方法可以有效地分离并获取同震重力效应和地震波信号,且估算的同震重力效应与理论模拟有较好的一致性,可为快速反演地震参数及地震预警提供更多的约束条件。