综合EGM2008模型和SRTM/DTM2006.0剩余地形模型的GPS高程转换方法

利用SRTM以及DTM2006.0全球地形模型构建剩余地形模型（RTM）数据,并将其转换为RTM高程异常。通过GPS/水准点的优化选择法,选择少量GPS/水准点的实测高程异常,扣除EGM2008模型以及SRTM与DTM2006.0模型求得的剩余模型高程异常,对残余高程异常进行拟合,从而进一步提高GPS高程转换的精度。最...     

基于Erdas Image 9.2 LPS区域网平差处理Spot5卫星影像实现方法

介绍基于LPS的正射影像处理流程,以图文的形式描述区域网平差处理Spot-5卫星影像的具体过程,最后得到正射纠正影像,用于1∶50 000DOM生产。     

遥感影像快速纠正系统的设计与实现

深入分析了传统遥感影像纠正处理工作中存在的问题,提出了以基础地理信息数据库为基础、基于网络环境的协同作业模式,解决了传统遥感影像纠正处理工作中资料准备工作量大、控制点采集效率低以及数据安全等问题。介绍了系统技术架构、设计与技术实现,为实现遥感影像快速纠正提出了切实可行的技术方案。     

SPOT5影像数据不同融合方法的比较与评价

采用小波IHS变换、小波PCA变换、EHLERS变换等五种不同融合技术对SPOT5的多光谱影像和全色影像进行融合,并从均值、标准差等方面对融合结果进行了评价。研究表明：EHLERS融合后影像有很好的整体视觉效果,但在细节表达方面有所缺陷;改进后的IHS融合后影像清晰度较低;PCA变换融合容易导致影像失真;而小波IHS和小波PCA融合技术以数据保留量大、失真程度小、视觉效果好、影像层次分明等特点证明了小波分解技术的优势。     

Laboratory experiments on along-slope flows in homogeneous and stratified rotating fluids

Laboratory experiments have been carried out for the flow along isobaths of simulated shelf-continental slope geometry. Cases of both homogeneous and linearly stratified fluids are considered and the background flows are sufficiently strong to have the flow near the bottom boundary range from transitional to fully turbulent. The background motions are impulsively started and flows with a coast on the right (spin-down) and on the left (spin-up) are considered. The homogeneous spin-down and spin-up processes are smooth in the sense that no vortical structures were found to be of the order of the slope width or larger. Flows reach equilibrium more quickly for spin-down cases, and this is attributed to secondary flows forced by the basin geometry. All of the stratified experiments exhibited large-scale instabilities as evidenced by the generation of slope and basin scale eddy structures and a much slower decay than their homogeneous counterparts.     

The Impact of Mid- and High-Latitude Rossby Wave Activities on the Medium-Range Evolution of the EAP Pattern During the Pre-Rainy Period of South China

Based on the NCEP DOE AMIP II daily reanalysis data (1979{2005), the evolution of the East Asia/Pacific(EAP) teleconnection pattern during the pre-rainy period of South China is studied on the medium-range time scale. It is found that positive and negative EAP patterns share a similar generation process. In the middle and upper troposphere, Rossby wave packets emanating from the northeast Atlantic or Europe propagate toward East Asia along the Eurasian continent waveguide and finally give rise to the three anomaly centers of the EAP pattern over East Asia. Among the three anomaly centers, the western Pacific subtropical center appears the latest. Rossby wave packets propagate from the high latitude anomaly center toward the mid-latitude and the subtropical ones. The enhancement and maintenance of the subtropical anomaly center is closely associated with the subtropical jet waveguide and the incoming Rossby wave packets from the upstream. In the lower troposphere, Rossby wave packets emanate from the subtropical Asia toward East Asia. Positive and negative EAP patterns could not be regarded as "mirrors" to each other with simply re- versed phase. For the positive pattern, the positive height anomaly center around the Scandinavia Peninsula keeps its strength and position during the mature period, and the Rossby wave packets thus propagate persistently toward East Asia, facilitating a longer mature time of the positive pattern. As for the formation of the negative EAP pattern, however, the incoming Rossby wave energy from the upstream contributes to both the enhancement and southeastward movement of the negative anomaly belt from the Yenisei River to the Bering Strait and the positive anomaly center around Mongolia. At the peak time, the two anomlous circulations are evolved into the Northeast Asia and the mid-latitude anomaly centers of the negative pattern, respectively. The energy dispersion of Rossby wave packets is relatively fast due to the predominant zonal circulation in the extratropics, causing a shorter mature period of the negative pattern. During the pre-rainy period of South China, the prevalence of the EAP pattern signiˉcantly affects the rainfall over the region south of the Yangtze River. The positive (negative) EAP pattern tends to causepositive (negative) precipitation anomalies in that region. This is di?erent from the earlier research findingsbased on monthly mean data.     

Effects of the low-frequency zonal wind variation on the high frequency atmospheric variability over the tropics

Recently, there is increasing evidence on the interaction of atmospheric high-frequency (HF) variability with climatic low-frequency (LF) variability. In this study, we examine this relationship of HF variability with large scale circulation using idealized experiments with an aqua-planet Atmospheric GCM (with zonally uniform SST), run in different zonal momentum forcing scenarios. The effect of large scale circulation changes to the HF variability is demonstrated here. The HF atmospheric variability is enhanced over the westerly forced region, through easterly vertical shear. Our study also manifests that apart from the vertical wind shear, strong low-level convergence and horizontal zonal wind shear are also important for enhancing the HF variance. This is clearly seen in the eastern part of the forcing, where the HF activity shows relatively maximum increase, in spite of similar vertical shear over the forced regions. The possible implications for multi-scale interaction (e.g. MJO–ENSO interaction) are also discussed.     

台风“卡努”的数值模拟与非对称结构的分析

热带气旋登陆过程中受到浅海区大陆架和海岸地形的影响,其结构将发生突变.本文用MM5模式模拟了0515号台风"卡努"登陆浙江的过程,表明MM5模式能很好地模拟出台风路径及其主要雨带.在结构上,登陆后主要完成了从基本对称的垂直分布到东西非对称分布的转换.在热力场方面,登陆后的相当位温、相对湿度、水汽通量散度都比登陆前更加有利于暴雨的发生,登陆后的东西两侧也演变为不对称的分布,东侧的水汽比西侧更充沛,同时东侧的大气层结更加不稳定.     

两种初始场MM5模式预报效果对比评估

为了解本地MM5模式的预报性能,根据其预报结果,检验了基于NCEP和T213两种初始场MM5模式在河北以及京津地区2007年8月至2008年1月的降水、日极值温度和相对湿度的预报效果。结果表明,MM5晴雨（雪）预报的准确率较高,具有较好的参考价值,而对于降水的分级预报,随着预报时效的延长和降水强度的增加,其可用性逐渐降低,但整体来看基于NCEP初始场的预报均比T213初始场预报效果明显;在日极值温度预报中,最低温度效果优于最高温度,T213初始场的预报对日最高温度预报的准确率较高,NCEP初始场的预报则在日最低温度预报中略胜一筹;对08：00相对湿度的预报,两者的预报效果基本相同,绝对误差都在15％左右。     

CINRAD/SA雷达开关组件故障分析处理

根据广州CINRAD／SA雷达发射机开关组件的一起故障现象,结合信号流程、电路原理图,深入元件一级,对故障的定位、检测及排除过程作了详细介绍,并对故障的成因作了推断分析,最后就雷达维护方面总结了一些经验,旨在对雷达技术保障人员提供参考和借鉴。