Universal birefringent filter with a new double passband mode     

Jingshan Wang  Guoxiang Ai  Guofeng Song  Bin Zhang  Xiangming Ye  Yingping Nie  Tzihong Chiveh  Weanshun Tsay  Huanshin Li 《Solar physics》1995,161(2):229-239

This article describes the universal birefringent filter (UBF) which will be mounted at Taiwan. The UBF permits observations of solar images, vector magnetic fields and/or line-of-sight velocity fields in any Fraunhofer line in the wavelength region from 4000 to 7000 with half width from 0.05 to 0.14 . We have tested it at ten Fraunhofer lines under a spectral telescope in Huairou Station of Beijing Astronomical Observatory and obtained the passband profiles. The principles of magnetic field and velocity field measurement with the UBF are also described.  相似文献   

中国近海以及邻近海域海洋再分析产品(CORA)中季节内变化的评估   总被引：5，自引：2，他引：3  

张敏  周磊  付红丽  姜良红  章向明 《海洋学报(英文版)》2016,35(3):90-101

A regional reanalysis product—China Ocean Reanalysis(CORA)—has been developed for the China's seas and the adjacent areas. In this study, the intraseasonal variabilities(ISVs) in CORA are assessed by comparing with observations and two other reanalysis products(ECCO2 and SODA). CORA shows a better performance in capturing the intraseasonal sea surface temperatures(SSTs) and the intraseasonal sea surface heights(SSHs) than ECCO2 and SODA do, probably due to its high resolution, stronger response to the intraseasonal forcing in the atmosphere(especially the Madden-Julian Oscillation), and more available regional data for assimilation. But at the subsurface, the ISVs in CORA are likely to be weaker than reality, which is probably attributed to rare observational data for assimilation and weak diapycnal eddy diffusivity in the CORA model. According to the comparison results, CORA is a good choice for the study related to variabilities at the surface, but cares have to be taken for the study focusing on the subsurface processes.  相似文献   

基于随机补片和DeepLabV3+的建筑物遥感图像变化检测     

王民水  孔祥明  陈学业  杨国东  王明常  张海明 《吉林大学学报(地球科学版)》2021,51(6):1932-1938

为有效解决传统遥感图像变化检测预处理复杂的问题,提出一种基于随机补片和DeepLabV3+的建筑物遥感图像变化检测方法。以ResNet50特征提取网络为基础,创建DeepLabV3+语义分割网络,并在图像和标签中创建大小为224像素×224像素的随机补片作为网络输入,训练建筑物提取网络;修改建筑物提取网络输入层为6通道,通过矩阵运算将两期遥感图像转换为一幅6通道非RGB图像,利用转换后的非RGB图像进行网络训练并验证变化检测精度。实验1利用ENVI5.3软件,采用马氏距离法进行变化检测;实验2采用改进的U-Net网络和随机补片,完成网络训练和精度验证;实验3使用实验2的训练数据和验证数据,采用随机补片和DeepLabV3+网络进行变化检测网络训练及精度验证。实验结果表明,该方法实验1、实验2、实验3建筑物变化检测平均交并比分别为24.43%、83.14%、89.90%,边界轮廓匹配分数分别为61.47%,80.24%、96.51%。  相似文献   

一次大暴雨过程低空急流脉动与强降水关系分析   总被引：16，自引：1，他引：16  

曹春燕  江崟  孙向明 《气象》2006,32(6):102-106

应用香港天文台提供的时空分辨率都非常高的风廓线雷达资料对深圳2005年8月19—20日大暴雨过程强降雨时段进行了详细分析。结果表明，风廓线雷达资料每小时风场揭示每次强降水的发生都对应一次西南急流的迅速加强和向下扩展。低空急流指数I可以说明低空急流的脉动向地面扩展程度与中小尺度降水的密切关系，对强降水的出现及雨强大小有一定的预示性。  相似文献   

利用雷达回波与GIS技术反演面雨量研究   总被引：5，自引：0，他引：5  

何健 王春林毛夏  孙向明 《气象科技》2006,34(3):336-339,i0002

自动气象站可以直接测量单点或较小范围的降水量,测量精度较高,但自动气象站的分布密度不够,往往漏掉强降水、暴雨中心。雷达能实时探测云和降水结构及系统发生、发展演变情况,能迅速提供一定区域的实时降水情况,但雷达测量误差较大,测定局地降水量精度不高,因此,将自动气象站与雷达进行点面结合,采用一定的数学方法和GIS技术,可以得到能够代表某特定区域平均降水情况的面雨量。以深圳市行政区域面雨量反演为例,建立区域内所有测站的6 min累积降雨资料与雷达回波数据之间的回归关系,借助GIS技术和包括对经度、纬度、海拔高度3个因子的地理订正,构建雷达图上特定行政区域的面雨量计算模型,并对格点拟合雨量进行空间分辨率的精细化反演,得到雷达图上的特定行政区域的面雨量图。  相似文献   

临安大气气溶胶理化特性季节变化   总被引：4，自引：2，他引：4       下载免费PDF全文

张养梅 颜鹏杨东贞  王淑凤汤洁俞向明  马千里 《应用气象学报》2007,18(5):635-644

分别利用碳成分分析仪、离子色谱仪和原子吸收光谱仪等获取浙江省临安地区大气气溶胶在春、夏、秋、冬四季的质量浓度、离子与碳成分特性，并对不同粒径气溶胶成分分布特点作了较详细分析。结果表明:气溶胶质量浓度、可溶性离子浓度以及碳成分浓度具有明显的季节变化趋势。整个尺度范围内，气溶胶质量浓度季节变化特点为春季浓度最高，达到534 μg/m3；冬季次之，质量浓度为117.21 μg/m3；夏季浓度最低，平均为65.7 μg/m3；秋季质量浓度98.6 μg/m3。可溶性离子成分在气溶胶中所占比例具有明显的季节性，其中夏季最高为49.4%，春季最低为11.3%。硫酸根离子SO₄2-和氨根离子NH₄+和硝酸根离子NO₃- 3种离子浓度之和约占离子总量的75%~83%。受温度影响，硝酸根离子NO₃-浓度随季节变化幅度较大，夏季平均浓度为1.7 μg/m3, 冬季平均浓度为11.5 μg/m3，是夏季浓度的6.8倍。碳浓度分布特点显示，气溶胶中元素碳浓度春季最高，夏季最低。有机碳浓度春季最高，冬季最低。气溶胶粒度分布特点也非常明显。四季中粒径小于11 μm（PM₁₁）的气溶胶均占气溶胶总量的90%以上，粒径小于2.1 μm（PM_2.1）的气溶胶占到气溶胶总量的53%以上。可溶性离子在粒径小于2.1 μm气溶胶颗粒中，以硫酸根离子、氨根离子和硝酸根离子为主。碳成分尺度分布特征为颗粒越小，有机碳及元素碳浓度越高。  相似文献   

察尔汗盐湖卤水中钾的放射性测定误差原因初步分     

王相明  祁永唐 《盐湖研究》1998,(1)

盐湖卤水中钾的放射性测定是一个复杂的工作过程,有许多因素影响着测量精度和稳定性,必须对各个方面综合考虑,最大限度地降低可能产生的干扰影响。本文分析了引起测定误差的主要因素,并提出了提高测量精度采取的措施。  相似文献   

南海海面高度变化及其与太平洋上涛动信号的关系   总被引：1，自引：1，他引：0  

PEI Yuhu  ZHANG Rong-Hu  ZHANG Xiangming  JIANG Lianghong  WEI Yanzhou 《海洋学报(英文版)》2015,34(12):80-92

本文使用循环平稳经验正交函数(CSEOF)方法分析了南海海面高度(SCS-SSH)的时空变化模态,并对它们与太平洋海盆尺度振荡的关系进行了探讨分析。结果表明,SCS-SSH的第一个CSEOF模态是季节变化模态,其变化强度受到一个与厄尔尼诺-南方涛动(ENSO)有关的低频信号的调制,即在厄尔尼诺期间季节变化的幅度减弱(最大可降低30%,1997/98)而在拉尼娜期间季节变化增强。SCS-SSH的第二个CSEOF模态是年际-年代际尺度的低频变化模态,其空间模态的月与月之间的差异微弱,而时间模态和太平洋年代际振荡(PDO)指数高度相关。然后,我们使用独立成分分析(ICA)方法提取了太平洋中的五个主要振荡成分,并检验了它们对SCS-SSH变化的各自影响。分析表明,纯粹的ENSO模态(类似于太平洋东部型ENSO)对SCS-SSH的低频变化的影响比较微弱,而ENSO的红化模态(类似于太平洋中部型ENSO)对SCS-SSH的低频变化具有明显影响。由于ENSO的红化模态是PDO信号的一个主要成分,这一结果解释了为什么在影响SCS-SSH的低频变化上PDO比ENSO更重要。径向鞍型振荡模态、黑潮延伸体处的增温模态、以及赤道的降温模态也由ICA方法提取出来,但它们对SCS-SSH低频变异的影响微弱。进一步的分析表明,太平洋的涛动信号可能以不同的方式来影响南海海面高度变化和海表温度变化。  相似文献   

Type III Bursts Associated with Millisecond Spikes Which Occurred Within the Frequency Range from 230 to 300 MHz     

Ma  Yuan  Xie  Ruixing  Zheng  Xiangming 《Solar physics》2001,200(1-2):157-166

The metric spectral data obtained at the Yunnan Observatory from July 1990 to December 1991 are analysed and some type III bursts associated with millisecond spikes are found. Their different morphologies reveal the relation between the type III bursts and the millisecond spikes. Based on the occurrence time and the characteristics of continuity and changes of the morphologies in the spikes and the type III bursts of two typical events, we verify that the acceleration region of the coronal electrons is located above the emitting region of the millisecond spikes and the type III bursts. The observations show that the interface frequency of a pair of type III bursts lies near 250 MHz. Finally the authors attempt to explain qualitatively the generating mechanism of the metric millisecond spike-type III bursts by means of the plasma hypothesis.  相似文献   

Climate change affecting temperature and aridity zones: a case study in Eastern Inner Mongolia, China from 1960–2008     

Jinwei Dong  Jiyuan Liu  Geli Zhang  Jeffrey B. Basara  Scott Greene  Xiangming Xiao 《Theoretical and Applied Climatology》2013,113(3-4):561-572

Recent climate change is substantially affecting the spatial pattern of geographical zones, and the temporal and spatial inconsistency of climatic warming and drying patterns contributes to the complexity of the shifting of temperature and aridity zones. Eastern Inner Mongolia, China, located in the interface region of different biomes and ecogeographic zones, has experienced dramatic drying and warming over the past several decades. In this study, the annual accumulated temperature above 10 °C (AAT10) and the aridity index, two key indicators in geographical regionalization, are used to assess warming and drying processes and track the movements of temperature and aridity zones from 1960 to 2008. The results show a significant warming at the regional level from 1960 to 2008 with an AAT10 increase rate of 7.89 °C·d/year (p?<?0.001) in Eastern Inner Mongolia, while the drying trend was not significant during this period. Spatial heterogeneity of warming and drying distributions was also evident. Analysis of warming and drying via piecewise regression revealed two separate, specific trends between the first 31 years (1960–1990) and the subsequent 18 years (1991–2008). Generally, mild warming and very slight wetting occurred prior to 1990, while after 1991 both warming and drying were significant and enhanced. Continuous warming drove a northward shift of temperature zones from the 1960s to 2000s, while aridity zones displayed enhanced temporal and spatial variability. Climate change effects on temperature and aridity zones imply that the patterns of cropping systems, macro-ecosystems, and human land use modes are potentially undergoing migration and modification due to climate change.  相似文献