GRAPES区域集合预报模式的初值扰动增长特征   总被引：4，自引：1，他引：3  

王婧卓  陈静  庄照荣  张涵斌  王静 《大气科学》2018,42(2):367-382

基于GRAPES-REPS（Global and Regional Assimilation and Prediction Enhanced System-Regional Ensemble Prediction System）区域集合预报模式和集合变换卡尔曼滤波（Ensemble Transform Kalman Filter,ETKF）初值扰动方法,对2015年6月1~15日10 km与15 km水平分辨率分别进行集合预报试验,通过分析ETKF初值扰动分量、初值扰动方差准确率、动能谱、扰动能量演变、日变化及集合离散度、均方根误差等特征,揭示GRAPES-REPS区域集合预报ETKF初值扰动结构及增长特征。结果表明:（1）ETKF初值扰动方案产生的扰动能够保持所有正交、不相关方向的误差方差,且ETKF分量α参数值及放大因子具有较好的稳定性。（2）ETKF初值扰动方法生成的扰动场以大尺度扰动为主,扰动结构及能量具有随流型依赖特征,低层以内能扰动为主,高层以动能扰动为主,且集合扰动可以有效捕捉预报误差的结构。（3）GRAPES区域集合预报初值扰动总能量和集合离散度随预报时效的延长均呈发展趋势,但离散度增长率小于均方根误差增长率,即集合预报总体存在集合离散度不足的问题。（4）水平分辨率提高可以增加中高层大尺度扰动波谱能量,明显改进等压面及近地面风场及温度场的集合预报效果。值得指出的是,GRAPES-REPS区域集合预报低层内能扰动能量存在明显的日变化特征,特别是青藏高原地区更加显著,需要进一步研究青藏高原初值扰动结构的合理性。  相似文献   

VP型垂直摆倾斜仪观测频带的分析及改进     

吕品姬  李正媛  耿丽霞  李农发  徐春阳 《大地测量与地球动力学》2020,40(5):540-545

从仪器原理、传递函数和观测数据等方面分析目前在网进行1 Hz采样的VP型垂直摆倾斜仪在2~60 s周期内的频率特性,认为该仪器可以观测到频带内的信号变化,但因处于过渡带,观测幅度较真实幅度削弱约20~40 dB。对VP型垂直摆倾斜仪观测频带进行拓展,使2~60 s周期内的观测信号由之前的过渡带进入到仪器的通频带,结果与相同采样率的其他定点形变仪器的观测效果相同,将地倾斜观测量转换为加速度表达后,其幅频特性符合全球地震背景噪声模型。改进后的VP型垂直摆倾斜仪对于远距离震级不大的同震体波震相记录效果略优于改进前,但受地脉动影响,在识别非地脉动信号时需要采用更精细的方法和手段来提高识别效果。  相似文献   

Using GIS-based distributed soil loss modeling and morphometric analysis to prioritize watershed for soil conservation in Bago river basin of Lower Myanmar   总被引：1，自引：0，他引：1  

Kay Thwe Hlaing  Shigeko Haruyama  Maung Maung Aye 《Frontiers of Earth Science》2008,2(4):465-478

Bago River is an important river in Myanmar. Although shorter than other rivers, it has its own river system, and people along the river rely heavily on it for their daily lives. The upper part of the watershed has changed rapidly from closed forest to open forest land in the 1990s. Since the recent degradation of the forest environment, annual flooding has become worse during the rainy season in Bago City. This paper aims at determining soil conservation prioritization of watershed based on soil loss due to erosion and morphometric analysis in the Bago Watershed by integrating remote sensing and geographic information system (GIS) techniques. In this study, soil erosion of the Bago watershed was determined using the Universal Soil Loss Equation. Such factormaps as rainfall, soil erodibility, slope length gradient, and crop management were compiled as input parameters for the modeling; and the soil loss from 26 sub-watersheds were estimated. Then, the soil erosion maps of the Bago watershed for 2005 were developed. The resulting Soil Loss Tolerance Map could be utilized in developing watershed management planning, forestry management planning, etc.  相似文献   

涂氏磷钙石的形成条件研究     

谢先德  陈鸣 《地球化学》2008,37(4)

用微束矿物学和激光拉曼光谱等分析测试技术,并结合人工高压实验结果,研究了我国随州陨石冲击熔脉中的白磷钙石高压相变形成涂氏磷钙石的必要条件,并对寺巷口陨石冲击熔脉中的白磷钙石虽与林伍德石、镁铁榴石和玲根石等高压矿物共生,但仅表现为结构损伤而未相变成涂氏磷钙石的原因进行了探讨.研究结果发现,随州陨石中白磷钙石或氯磷灰石的存在是涂氏磷钙石得以形成的物质前提,陨石熔脉中高达24 GPa和2000℃以上的高压高温环境是涂氏磷钙石能够形成的条件保障,而压力释放后熔脉极快的冷却速率是涂氏磷钙石得以淬火并稳定保存的关键.研究还查明,寺巷口陨石冲击熔脉比随州陨石的熔脉要宽1至2个量级,其冷却速率比随州陨石慢得多,因此,熔脉中早先形成的涂氏磷钙石,可能在脉内较高的冲击后温度影响下,慢慢退变质成白磷钙矿.  相似文献   

珊瑚骨骼生长研究评述     

张江勇  余克服 《地质论评》2008,54(3):362-372

珊瑚骨骼生长有年、月、日周期,能够当作古生物钟来记录地质历史。块状珊瑚骨骼密度条带年周期的发现对后来的珊瑚古气候研究产生了深远的影响,随后又发现世界各热带海域的珊瑚存在多种多样的骨骼密度变化模式,起先常从珊瑚的生长环境中寻找骨骼密度变化的控制因素,但是没有成功,从80年代后期,部分学者试图从珊瑚骨骼构架本身出发、综合考虑环境因素和骨骼密度条带之间的关系来探求骨骼密度变化的机理,并提出了一个可以解释大多数块状珊瑚骨骼密度条带变化模式的骨骼生长模型。块状珊瑚软体层厚度是一个十分重要但至今仍没引起足够重视的珊瑚生长参数,它相对于骨骼线性生长率的变化影响着骨骼密度变化模式。骨骼钙化作用和虫黄藻光合作用的相互关系还存有争议,珊瑚骨骼钙化机理仍在探索中。  相似文献   

三峡水库对大宁河沉积环境的影响——碳酸盐和常量元素含量的变化     

吴旭东  李红春  李俊云  刘子琦  王勇  李廷勇  高彦芳 《地质论评》2008,54(3):419-426

对2006年10月采自长江巫山段一级支流大宁河河底的三根岩芯作了常量元素（K、Na、Ca、Mg）的分析。研究结果表明,沉积物中稀酸可溶相常量元素的含量能够反映沉积物的特征和来源。大宁河中—上游沉积物中碳酸盐含量平均为23%,反映岩溶地区石灰岩风化的影响;而与长江交接处的沉积物中碳酸盐含量平均为10%,显示长江主流有明显不同的沉积物来源。三峡大坝的建成蓄水,水位提高,使得碳酸盐含量低的红色粘土进入双龙镇段大宁河沉积,造成碳酸盐含量、稀酸可溶相常量元素含量急剧下降、沉积物的颜色发生显著变化。受到蓄水作用的影响,大宁河泥沙沉积速率大幅度提高,自2004年12月蓄水以来,大宁河双龙镇附近沉积物厚达10cm以上。  相似文献   

Spatio-temporal evolution of Coulomb stress in the Pacific slab inverted from the seismicity rate change and its tectonic interpretation in Hokkaido, Northern Japan     

Subesh Ghimire  Kei Katsumata  Minoru Kasahara 《Tectonophysics》2008,455(1-4):25-42

We estimated spatio-temporal evolution of Coulomb stress within the subducted Pacific slab in Hokkaido from the analysis of seismicity rate change. For this purpose we used earthquake catalog from the Institute of Seismology and Volcanology (ISV), Hokkaido University for the period 1993/4/1–2006/12/31 after relocating to compensate location errors due to the heterogeneous P- and S-wave structure beneath Hokkaido. We found that spatial pattern of Coulomb stress change inverted from the seismicity rate change is comparable with static change in Coulomb stress estimated from dislocation models. Our results and analyses reveal important insights on spatio-temporal pattern of deformation of the subducted Pacific slab in terms of Coulomb stress change. We found that the 2003 Tokachi Oki earthquake (Mw = 8.0) pervasively perturbed Coulomb stress in a regional scale with a significant impact to trigger the 2004 Kushiro Oki earthquake. The 2004 Kushiro Oki earthquake (Mw = 7.0) is another significant stressing event that changed the pattern of Coulomb stress in the area. We found that stressing events with magnitude smaller than 7.0 has minimal impact on Coulomb stress change in the Pacific slab. Similarly, comparatively deep focused large earthquakes could not change Coulomb stress significantly. Further the pattern of Coulomb stress change after the 2003 Tokachi Oki earthquake correlates the pattern of afterslip distribution in Hokkaido.  相似文献   

西汉末—北宋黄河三角洲（公元11～1099年）的沉积记录   总被引：2，自引：0，他引：2  

薛春汀  李绍全  周永青 《沉积学报》2008,26(5):804-812

西汉末—北宋黄河三角洲是在很浅的水域发育的。在1855年海岸线内侧数千米处三角洲厚度只有12 m左右。无论是整个三角洲,还是水下三角洲各个组成部分（前三角洲、三角洲前缘）都比现代黄河三角洲相应部分要薄。前三角洲之上在不同地点发育三角洲前缘粉砂或者分流间湾黏土质粉砂。推测这一时期三角洲上多条分流同时活动。三角洲中有孔虫和介形虫属种和数量都与下伏陆架沉积物的有明显差别,且自下而上显示越来越受入海河水影响。与苏北、现代黄河三角洲沉积物中生物丰度的比较可以看出沉积速率的增加,反映这一历史时期黄河入海泥沙增加以及黄土高原侵蚀越来越严重。  相似文献   

Experimental research on the influence of two cultivation practices on rainfall runoff- and （sandy and muddy） sediment-generating processes in purple soil environment     

XU Pei  ;WANG Yukuan  ;FU Bin 《中国地球化学学报》2008,27(4):370-376

Rainfall simulations have been conducted to study the soil erosion process of purple soil in two cultivation practices---contour cultivation and downslope cultivation. Results showed that under the two cultivation practices, the surface runoff can be described by the logarithmic function formula. In the initial period of rainfall, the amount of runoff increased with the rainfall duration and 20 minutes later it became relatively constant. The changing process of soil erosion rate may be described by the logarithmic function formula. The erosion rate increased with the rainfall duration and 20 minutes later it also became constant. Under downslope cultivation condition, the soil erosion rate increased more significantly than that under contour cultivation condition in the case of gentle rainfall intensity, and there is no obvious difference in erosion rate for downslope cultivation and contour cultivation practices. However, with increasing rainfall intensity the soil erosion rate under the downslope cultivation condition could be more than 30 times that under the contour cultivation condition. But this kind of difference would be reduced to some extent in the case of heavy rain.  相似文献   

不同长度基线的电离层处理策略     

周颖  满小三  李郴 《测绘工程》2017,26(1)

针对不同长度的基线,受双差之后电离层延迟影响不同,提出一种新的电离层处理策略。对短、中、长基线处理分别采用3种不同的数学模型:电离层固定模型,电离层加权模型,电离层浮点模型。通过3组不同长度基线实测数据处理表明,对应不同长度的基线,文中策略可以有效地提高模糊度固定率及定位精度。  相似文献