华东地区气溶胶分布和变化特征研究     

刘璇  朱彬  关学锋  袁亮 《沙漠与绿洲气象(新疆气象)》2017,11(1):11-21

利用中分辨率光谱仪(MODIS)获得的气溶胶光学厚度(AOD)、细粒子比例(FMF)和臭氧检测仪(OMI)获得的气溶胶指数(AI)统计分析了2005—2014年我国华东地区气溶胶光学性质的时空分布特征,同时利用潜在源分析(PSCF)模型对我国华东地区AOD和AI的潜在源区进行分析。研究结果表明:华东地区的AOD、FMF和AI时空分布存在较大的差异,2005—2014年AOD和AI的平均值高值主要分布在华东地区北部,FMF的高值区则分布在华东南部地区;10 a间华东地区AOD呈现出先升高后降低的趋势,FMF波动幅度不明显,AI值有所上升;整个华东地区AOD的季节变化较为明显,春夏两季AOD明显高于秋冬两季。华东北部和中部地区夏季由于较高的相对湿度,AOD最大可达0.8以上。而在华东南部地区,夏季受到降水的影响,AOD维持在0.2~0.4之间。FMF季节变化趋势与AOD不同,夏季最大达到0.58,春季最小仅为0.26。AI平均值在冬季最大高达0.63,夏季最小,为0.27。PSCF分析显示华东地区AOD主要源区以局地排放为主,同时也存在由河南、湖北和湖南等周边省市近距离输送影响;AI以局地和北方远距离输送为主,同时也受到河南、湖北等周边省市近距离输送的影响。  相似文献   

2.63.8GHZ太阳微波爆发中的精细结构     

宁宗军  傅其骏  陆全康 《紫金山天文台台刊》1999,(2)

微波Ⅲ型爆发和微波尖峰辐射是太阳微波爆发中两个主要的精细结构,由于微波段比长波段的情况更复杂,单从形态上很难区分。１９９４ 年Ｉｓｌｉｋｅ ＆ Ｂｅｎｚ 给出１３ＧＨｚ 频带上的各类爆发分类定义,本文参考了其中关于微波Ⅲ型爆发和微波尖峰辐射的分类,分析北京天文台２ ．６３ ．８ＧＨｚ 频带上观测到的微波尖峰辐射的精细结构,发现该定义有局限性,重新定义了本波段上的微波Ⅲ型爆发和微波尖峰辐射,并讨论了这种分类定义与设备时间分辨率的关系  相似文献   

江西省新一代中短期预报业务流程介绍     

张瑛  许爱华 《气象与减灾研究》2005,28(1):22-24

按照中国气象局以数值预报产品为基础,以MICAPS预报人机交互系统为工作平台的思路．建立了包括气候背景、预报思路、天气会商、预报制作和管理5个模块的江西省新一代中短期预报业务流程,并重点介绍了数据转换、综合图定义、参数修改、网络改造等有关的本地化工作,以及包括天气形势描述、要素预报的人机交互修改、全省实况描述的预报制作和预报产品自动或半自动生成技术。  相似文献   

官厅水库秋季悬浮颗粒物和CDOM吸收特性   总被引：2，自引：0，他引：2  

雷霞  郭子祺  田野  谢飞  秦静欣 《湖泊科学》2013,25(6):883-891

利用2012年9月5日在官厅水库采集的水体吸收系数数据,对总悬浮颗粒物、浮游植物色素颗粒物、非色素颗粒物和有色可溶性有机物的吸收特性进行研究.结果表明:秋季官厅水库的颗粒物吸收以浮游植物色素吸收为主,总颗粒物吸收光谱与浮游藻类吸收光谱相似;非色素颗粒物和有色可溶性有机物的吸收系数随波长的增大接近指数规律衰减;a_d(440)、a_d(675)与C_Chl.a呈显著相关,表明官厅水库秋季的非色素颗粒物主要来源于浮游藻类降解产物,陆源性输入较少;a ph(440)、a ph(675)与C_Chl.a存在显著线性关系,但其比吸收系数较为恒定,与C_Chl.a基本无关;不同采样点的不同组分吸收系数对总吸收系数的贡献不同,大致有4种表现类型.在富营养程度较高的妫库区,浮游植物色素是水体光谱吸收的主导因子;在富营养程度较低的中库区,颗粒物与有色可溶性有机物共同主导水体光谱吸收.  相似文献   

Transport of moderately sorted gravel at low bed shear stresses: The role of fine sediment infiltration          下载免费PDF全文

Emeline Perret  Céline Berni  Benoît Camenen  Albert Herrero  Kamal El Kadi Abderrezzak 《地球表面变化过程与地形》2018,43(7):1416-1430

A reliable estimation of sediment transport in gravel‐bed streams is important for various practical engineering and biological studies (e.g., channel stability design, bed degradation/aggradation, restoration of spawning habitat). In the present work, we report original laboratory experiments investigating the transport of gravel particles at low bed shear stresses. The laboratory tests were conducted under unsteady flow conditions inducing low bed shear stresses, with detailed monitoring of the bed topography using a laser scanner. Effects of bed surface arrangements were documented by testing loose and packed bed configurations. Effects of fine sediments were examined by testing beds with sand, artificial fine sand or cohesive silt infiltrated in the gravel matrix. Analysis of the experimental data revealed that the transport of gravel particles depends upon the bed arrangement, the bed material properties (e.g., size and shape, consolidation index, permeability) and the concentration of fine sediments within the surface layer of moving grains. This concentration is directly related to the distribution of fine particles within the gravel matrix (i.e., bottom‐up infiltration or bridging) and their transport mode (i.e., bedload or suspended load). Compared to loose beds, the mobility of gravel is reduced for packed beds and for beds clogged from the bottom up with cohesive fine sediments; in both cases, the bed shear stress for gravel entrainment increases by about 12%. On the other hand, the mobility of gravel increases significantly (bed shear stress for particle motion decreasing up to 40%) for beds clogged at the surface by non‐cohesive sand particles. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Fault geometrical model of Dujiangyan section in Longmenshan fault zone          下载免费PDF全文

Hu-Rong Duan  Sheng-Lei Chen  Run Li  Quan-Chao Yan 《地震科学（英文版）》2018,31(3):126-136

The focal mechanism solution on the seismic fault plane can reflect the geometric and kinematic characteristics of faults, and it is an important way to further study the fine structure of fault plane. From the focal mechanism solution of the earthquakes around the Dujiangyan fault in Longmenshan fault zone, we derived the average dip angle of Dujiangyan fault is 45.1° based on the seismic moment tensor theory. In order to refine the fault geometry structure, this paper decomposed it into multiple sub-fault planes along the length and width of the fault plane and forms a number of models A13, B13, A23 a, A23 b, A23 c, B23 a,B23 b and B23 c, then calculated the sub-fault's dip of each model. In order to clarify exactly which one of the fault models is closest to the real fault model, the fault slip was carried out for each model in turn, then compared the surface displacement of each model with GPS observations. The results show that B23 c model with high dip in shallow and small dip in deep is the best model, the lengths of each subfault of Dujiangyan fault from south to north are 33 km, 21 km and 46 km, respectively. When the depth of the fault bottom is about 11 km, the dip angles are 70.56°, 67.41° and 45.55°.When the depth of the fault bottom is about 30 km, The fault dip angles are 44.55°, 29.18° and 44.25°.  相似文献   

实景三维精细建模优化方法探索与实践     

吴昌 《测绘与空间地理信息》2022,(2):130-131,134

对比分析目前常用的几种实景三维建模方法及适用性,剖析倾斜摄影三维建模技术在几何结构和模型纹理等方面存在的问题,提出了实景三维精细建模的优化方法和技术路线,着重阐述了高低空航摄相结合的关键技术,明显改善了模型效果,提高了建模的质量与效率,为实景三维数字城市建设提供了技术参考.  相似文献   

基于EC细网格产品在乌鲁木齐机场低能见度预测中的释用     

王楠 《沙漠与绿洲气象(新疆气象)》2020,14(2):81-89

利用2015—2018年乌鲁木齐机场航空例行天气报告(METAR报)、ECMWF(European Centre for Medium-Range Weather Forecasting)细网格数值预报产品对影响能见度的主要因子进行分析,提取与低能见度相关性高的物理量作为预报因子,采用SVM方法,分别基于Poly、RBF核函数建立乌鲁木齐机场未来21 h能见度预报模型。结果表明:(1)基于预报因子区间分类的SVM模型物理意义明确,试验结果较好;以RBF为函数建立的SVM模型(SVM-RBF)预报能力更好,其训练样本预测的TS评分0.84,准确率89.20%。(2)SVM-RBF模型的检验样本中,预报准确样本的预报误差整体偏小;在漏报样本中则有能见度越低、预报误差越大的特点,模型的振荡性明显。(3)结合NCEP/NCAR再分析资料研究SVM-RBF模型对天气过程的预报表现,发现模型对于特定天气形势下引发的低能见度天气,预报误差较小且预报提前量较大。  相似文献   

Provenance discrimination of fine sediments by mid-infrared spectroscopy: Calibration and application to fluvial palaeo-environmental reconstruction     

Stoil Chapkanski  Damien Ertlen  Claire Rambeau  Laurent Schmitt 《Sedimentology》2020,67(2):1114-1134

Determining sediment provenance allows a better understanding of fluvial palaeo-dynamics, and identifying involved watersheds, at broad spatio-temporal scales. Conventional approaches for source identification are usually based on the physical, mineralogical, geochemical, magnetic or isotopic properties of sediments. Rapid, non-destructive and, in well-established contexts, highly accurate, mid-infrared spectroscopy is an alternative method for investigating sediment sources. The present research objectives are: (i) to use the mid-infrared spectroscopy method to discriminate the provenance of fine sediments, by applying discriminant analysis on a large set of reference samples from three different watersheds in the Upper Rhine area (associated with the Rhine, Ill and Vosges tributaries); (ii) to clarify whether the provenance spectra signatures are influenced by riverine depositional contexts (bars versus banks) and, to some extent, by grain size and/or high organic matter content; and (iii) to apply the mid-infrared spectroscopy – discriminant analysis method to a study of fluvial palaeo-dynamics and determine the provenance of palaeo-channel infillings. Three main sedimentary sources, divided into eight sub-categories, have been characterized by 196 modern reference samples from 78 collecting sites. Discriminant analysis displayed a strong separating power by classifying correctly the origin of samples without any inter-group overlap, independently from the geomorphological context (bar or bank) and associated slight changes in organic matter contents or grain size. Mid-infrared spectroscopy – discriminant analysis investigations of the palaeo-channel infill, complemented by radiocarbon dates and mineralogical data, allowed reconstructing general trends for the local morpho-sedimentary dynamics over the last ca 12 millennia.  相似文献   

断裂带首波研究进展          下载免费PDF全文

杨微 《地震工程学报》2019,41(6):1407-1418

断裂带首波是沿着存在物性差异界面传播的一种地震折射波,在传播过程中携带了断裂带的重要信息,对分析和研究断裂带以及附近区域的精细结构提供了一种新的分析方法。本文主要阐述断裂带首波的产生原理、波形特征、识别及分析方法等,介绍目前国际上识别及利用断裂带首波开展断裂带特征方面的研究现状,并针对地震危险区域存在物性差异的断裂带,提出可结合密集台阵观测技术,利用断裂带首波进行断裂带精细结构探测及其变化监测研究,提高潜在孕震环境及发生机理的认识水平。  相似文献