Parameter estimation in ensemble based snow data assimilation: A synthetic study

Estimating erroneous parameters in ensemble based snow data assimilation system has been given little attention in the literature. Little is known about the related methods’ effectiveness, performance, and sensitivity to other error sources such as model structural error. This research tackles these questions by running synthetic one-dimensional snow data assimilation with the ensemble Kalman filter (EnKF), in which both state and parameter are simultaneously updated. The first part of the paper investigates the effectiveness of this parameter estimation approach in a perfect-model-structure scenario, and the second part focuses on its dependence on model structure error. The results from first part research demonstrate the advantages of this parameter estimation approach in reducing the systematic error of snow water equivalent (SWE) estimates, and retrieving the correct parameter value. The second part results indicate that, at least in our experiment, there is an evident dependence of parameter search convergence on model structural error. In the imperfect-model-structure run, the parameter search diverges, although it can simulate the state variable well. This result suggest that, good data assimilation performance in estimating state variables is not a sufficient indicator of reliable parameter retrieval in the presence of model structural error. The generality of this conclusion needs to be tested by data assimilation experiments with more complex structural error configurations.     

国家地震灾情调查系统探讨

本文论述了我国目前地震灾情调查的现状以及地震应急所存在的问题,通过剖析这些问题,提出了我国地震灾情调查系统的框架设计,并详细介绍了国家地震安全社会服务工程项目中已实现的地震灾情调查系统.同时,考虑到新型技术发展所带来的机遇,对国家地震灾情调查平台的手段进行了更深入的拓展讨论.     

PM2.5监测及评价研究进展

综合阐述了近年来国内外PM2.5的监测方法、观测站网建设发展,以及PM2.5对人体健康、大气环境及天气、气候等方面的影响研究,并对国内外PM2.5空气质量标准差异进行了比较分析,提出了加强PM2.5监测及影响评价的建议.     

一次秋季暖云微物理结构探测试验

针对2008年10月24日四川盆地上空未形成降水的低层暖云,利用夏延ⅢA飞机搭载的PMS系列探头进行了探测试验,分析了云的微物理结构.分析结果表明:云体构成以小云滴为主,大云滴浓度较低,降水粒子很少.云中小云滴的液态含水量、数浓度、直径在水平方向上分布不均.小云滴的液态含水量和小云滴的体积平均直径正相关.相对云上部,云...     

渤海海域莱州湾凹陷构造演化对油气成藏的控制作用

莱州湾凹陷近年获重大油气发现,但构造演化特征复杂,烃源岩、沉积体系展布特征以及油气运聚规律认识尚不够深入.本文利用多种钻井资料,结合区域地质研究,首先对本区构造演化所产生的断裂与圈闭特征进行分析,划分出3级断裂体系以及3种类型圈闭,并深入研究了构造演化对油气生成与演化、优质储盖组合的分布以及油气运移与聚集的控制作用,总...     

Evidence for Palaeozoic magmatism recorded in the Late Neoproterozoic Marlborough ophiolite,New England Fold Belt,central Queensland

The ultramafic‐mafic complex in the Marlborough terrane of the northern New England Fold Belt is dominated by members of a Neoproterozoic (ca 560 Ma) ophiolite (V1). The ophiolite has been intruded by the products of three Palaeozoic tectonomagmatic episodes (V2, V3 and V4). The V2 magmatic episode is represented by tholeiitic and calc‐alkaline basalts and gabbros of island‐arc affinities. Sm/Nd isotopes give a whole‐rock isochron age of 380 ± 19 Ma (2σ) to this episode, some 180 million years younger than the V1 ophiolitic rocks. The V3 magmatic episode includes tholeiitic and alkali basalts with enriched geochemical signatures characteristic of intraplate volcanism. A whole‐rock Sm/Nd isochron age of 293 ± 35 Ma is obtained for this event. A fourth magmatic event (V4) is represented by basaltic andesites and siliceous intrusives with geochemical features similar to modern adakites. This event has its type locality in the Percy Isles. These data provide tectonic and geochronological constraints for the previously enigmatic Marlborough terrane and as such contribute to the ever‐evolving understanding of New England Fold Belt development.     

青藏公路沿线热喀斯特湖分布特征及其热效应研究

热喀斯特湖的出现和发育是多年冻土变暖的指示器,研究热喀斯特湖发育及其热效应是应对青藏高原气候变化和人类活动诱发冻土灾害的基础工作.基于SPOT-5卫星影像资料,在ArcGIS平台下解译遥感影像,获取了青藏公路沿线楚玛尔河至风火山段热喀斯特湖的数量和分布特征,这些热喀斯特湖以楚玛尔河高平原和北麓河盆地为主要分布区,且80％发育于高含冰量多年冻土区.热喀斯特湖通过竖向和侧向2种传热方式影响多年冻土,竖向传热会造成其下部多年冻土融穿,侧向传热会造成湖岸多年冻土增温,扩大热影响范围.通过北麓河地区一典型热喀斯特湖的数值计算,湖全年都在向湖岸放热.当热喀斯特湖离路基较近,将会对公路产生潜在或者直接的危害,其侧向热侵蚀往往会导致冻土路基温度升高,诱发路基病害.     

Landslide susceptibility mapping using rough sets and back-propagation neural networks in the Three Gorges, China

In the Three Gorges of China, there are frequent landslides, and the potential risk of landslides is tremendous. An efficient and accurate method of generating landslide susceptibility maps is very important to mitigate the loss of lives and properties caused by these landslides. This paper presents landslide susceptibility mapping on the Zigui-Badong of the Three Gorges, using rough sets and back-propagation neural networks (BPNNs). Landslide locations were obtained from a landslide inventory map, supported by field surveys. Twenty-two landslide-related factors were extracted from the 1:10,000-scale topographic maps, 1:50,000-scale geological maps, Landsat ETM + satellite images with a spatial resolution of 28.5 m, and HJ-A satellite images with a spatial resolution of 30 m. Twelve key environmental factors were selected as independent variables using the rough set and correlation coefficient analysis, including elevation, slope, profile curvature, catchment aspect, catchment height, distance from drainage, engineering rock group, distance from faults, slope structure, land cover, topographic wetness index, and normalized difference vegetation index. The initial, three-layered, and four-layered BPNN were trained and then used to map landslide susceptibility, respectively. To evaluate the models, the susceptibility maps were validated by comparing with the existing landslide locations according to the area under the curve. The four-layered BPNN outperforms the other two models with the best accuracy of 91.53 %. Approximately 91.37 % of landslides were classified as high and very high landslide-prone areas. The validation results show sufficient agreement between the obtained susceptibility maps and the existing landslide locations.     

Experimental investigation on soil carbon, nitrogen, and their components under grazing and livestock exclusion in steppe and desert steppe grasslands, Northwestern China

Livestock grazing is one of the main causes for the change of soil organic carbon (SOC) and total nitrogen (TN) in the arid and semi-arid parts in northern China. This paper examined the SOC, TN, and their components of the local steppe and desert steppe, considering continuous grazing and 4-year livestock exclusion, respectively. In steppe where livestock is excluded, both SOC and TN in the topsoil (0–0.20 m) are found to remain unchanged; however, significant growths are found in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), particulate organic carbon (POC), and particulate organic nitrogen (PON). On the contrary, both POC and PON progressively decrease at the continuous grazing sites, attributed to the reduction of the mass proportions of soil particulate fraction in the top 0.10 m soil. In the desert steppe where grazing is excluded, the SOC, TN, and their components of the topsoil increase. However, at the continuous grazing sites, POC and PON in the 0.10 m topsoil are reduced, caused by the decrease of C and N content in soil particulate fraction. Besides, microbial quotients were lower in the continuous grazing sites in the two grasslands. It is also found that both MBC and POC are more sensitive to human-induced activities than SOC, and thus could serve as earlier indicators of the soil-fertility variation caused by short-period grazing management.