基于BP人工神经网络的震前电离层VTEC异常扰动研究

利用BP神经网络建立电离层VTEC模型,以年积日(DOY)、世界时(UT)、电磁KP数、Dst数、AP数、太阳黑子数(SSN)作为网络输入层参数,通过BP神经网络的训练和泛化功能,提供地震前10天理论意义上的平静VTEC值,再与地震前10天的实测VTEC作比较。试验结果表明,在地震发生之前3～5天电离层VTEC数值较VTEC平静时刻增大20%左右。     

2010-08-01太阳风暴对电离层及GPS测量的影响分析

利用GPS电离层探测技术分析了2010-08-01太阳风暴对全球电离层VTEC造成的扰动异常影响。受朝向地球的日冕物质抛射影响,08-03首先对北美地区电离层VTEC产生扰动异常,最大值达到15TECu。由于地球自转,发生电离层VTEC异常集中的区域会随太阳直射点向西移动,一般发生于其所在区域的地方时13:00～17:00。另外,还分析了此次太阳风暴对GPS观测数据质量及电离层高阶项误差的影响。结果表明,此次太阳风暴期间,GPS观测数据质量并未受到明显的影响,但使得L1、L2载波的电离层高阶项误差增大,误差影响达到cm级。     

利用GPS载波相位观测值建立区域电离层模型研究

介绍利用载波相位观测值建立区域电离层模型的理论和方法，讨论该模型在实现过程中需要注意的问题，结合具体算例与利用伪距观测值计算的电离层模型的精度进行比较。     

2012-04-11苏门答腊地震同震电离层异常研究

2012041108:38:37UT和10:43:09UT苏门答腊地区先后发生了M8.6级和M8.2级强烈地震。本文采用震中附近地区9个IGS连续跟踪站的GPS观测数据,对两次地震的同震电离层异常现象进行了探测与分析。结果表明两次地震之后均出现了明显的同震电离层异常现象,异常出现的时间和异常的幅度与距震中的距离有关,异常的最大值约为2TECU,且震中偏北方向的异常最为显著。根据震中到穿刺点的距离,计算得出两次地震产生的大气声波的传播速度分别为0.73±0.06km/s和0.69±0.04km/s,与声波在0～450km内的平均传播速度一致。     

地基GPS区域电离层多项式模型与硬件延迟统一解算分析

探讨了利用区域地基GPS双频精码数据建立单层电离层多项式模型中,多项式系数、组合硬件延迟统一平差的数据处理方法.数据分析表明,GPS卫星短弧段的天空视图对电离层多项式建模的影响较大,由此估计的组合硬件延迟解不稳定,电离层模型也存在系统误差,边际效应明显;分段常数的全天电离层延迟多项式建模的数据处理方法可以有效地削弱短时弧段建模的影响,获取一致性、稳定性更好的组合硬件延迟.     

东日本大地震电离层异常分析

目前空基和路基等电磁信号探测手段已经应用于地震电离层异常的探测。自从GPS数据可以用于计算电离层电子总量(TEC), 这项技术被广泛关注的同时作为一个可行的手段用于探测地震前后电离层异常。本文利用东日本大地震震中附近多个IGS网络站点的数据, 分析2011年3月11日发生的Mw9.0东日本大地震震区上空电离层信息, 计算出TEC时间序列并进行波谱分析、包络线法异常分析、全球电离层异常地图绘制及震后3 h扰动异常分析。通过分析发现, 震前存在明显的电离层异常, 在3月8日即震前第3天存在异常;同时也计算了震后3 h的各站与卫星路径上等价TEC的P₄值;且多个站与多星路径上存在着明显的电离层扰动异常, 并且不断远离震中, 能量逐渐衰减, 证明电离层异常的发生与地震有较明显的关系。     

利用GPS组合观测值建立区域电离层模型研究

介绍了VTEC模型的基本原理，给出了三种利用载波相位观测值改善伪距观测值精度的方法，利用三种组合观测值分别建立VTEC模型，并与利用伪距观测值计算的VTEC模型的精度进行比较。     

基于格网的GPS/ BD-2组合系统电离层VTEC模型研究

本文利用中国地壳运动观测网络的GPS数据,兼顾卫星发射频率硬件延迟影响,模拟了BD-2系统的电离层VTEC,并建立GPS/ BD-2组合系统的VTEC格网模型,实验结果证实了该模型在电离层延迟短时间预报上的有效性.     

基于GPS数据的震前电离层异常分析

首先利用日本及周边区域IGS站提供的GPS观测数据,计算得到了测站上空垂直总电子含量VTEC的时间序列.采用滑动平均法与非滑动平均法两种统计学方法针对日本境内某震例进行了震前VTEC值异常分析,数值结果表明地震震前出现了电离层异常现象.此外,为了探讨异常情况与地震的相关性,进一步分析了电离层异常的全球空间分布.最后,通过对比两种异常检验方法的分析结果可知,两种方法分析结果的总体趋势一致,验证了本文结果的可靠性.     

基于GPS的2003年10月28日太阳耀斑的电离层响应研究

本文利用VTEC(the Vertical Total Electron Contents)增量和VTEC变化率分析了电离层在2003年10月28日太阳耀斑期间中国的四个IGS跟踪站的响应情况.通过分析比较说明用VTEC变化率似更适合探测电离层对太阳耀斑的响应,并有望发现耀斑期间电离层的一些扰动现象,但在能得到高精度的绝对离层延迟的情况下,利用VTEC增量能准确全面地反映电离层对耀斑响应的整体变化情况.     

中国南极中山验潮站记录到的2004年印度洋海啸事件

2004年12月26日发生在印度尼西亚苏门答腊岛至印度安达曼群岛西侧海沟的大地震达9级或者9级以上,引发的海啸造成了空前的灾难。本文利用中国南极中山验潮站2004年12月26日至29日的验潮数据,记录到了此次印度洋大海啸事件。海啸通过印度洋于震后12小时达到南极中山站海域,海啸最大波高约40 cm。     

Seasonality and Latitudinal Variation of Water Vapour and Aerosol Optical Thickness and Their relationship Over Tropical Indian Ocean

Aerosol and water vapour are very important element in the Earth’s climate system which has direct role in the Earth’s radiation budget. In this paper the seasonality, latitudinal distribution and the relationship of aerosol optical thickness (AOD) and water vapour (WV) using MODIS Level 3 monthly data from 2001 to 2008 are analysed. The analysis shows that AOD (0.55 μm) values reach maximum during southwest monsoon and remain minimum during northeast monsoon period. The Equatorial Indian Ocean shows minimum AOD (0.115 to 0.153) throughout the year compared to Arabian Sea (0.208 to 0.613) and Bay of Bengal (0.214 to 0.351). Arabian Sea shows high variation and maximum value of AOD compared to Bay of Bengal and Equatorial Indian Ocean. During southwest monsoon WV over Bay of Bengal was found higher in concentration compared to Arabian Sea and Equitorial Indian Ocean throughout the study period. Comparison between Arabian Sea (2.98 cm to 5.07 cm) and Bay of Bengal (3.49 cm to 5.94 cm) shows that WV concentration is less in Arabian Sea throughout the year. The analysis of correlation between WV and AOD was found to be inconsistent. However, AOD and WV shows a strong positive correlation for whole year (Mean R² =0.90) in the Equitorial Indian Ocean region except in the months of January, February and March. In general, the correlation between WV and AOD is found to be strongly positive for oceanic aerosol (sea salt) in low water vapour condition.     

Optimum tracking of ship routes in 3g-WAM simulated rough weather using IRS-P4 (MSMR) analysed wind fields

Rough weather ship routing is studied using model hindcast wave climate. With the launch of IRS-P4 (OCEANSAT-I), it became possible to carry out routine wave forecasting over the Indian Ocean. The MSMR channel of the satellite gives scalar wind, which is analysed at National center for Medium Range Weather Forecasting (NCMRWF), India for converting to vector winds. The same is used as input to third generation wave model for the rough weather month of July 2000. Simulations are carried out using Cycle-4 of third generation spectral wave model WAM for regional grid system. This simulated wave climate formed the basis for computing effective ship velocity in the irregular seaway. This study gives a quantitative estimation of change in ship velocity in the open Indian Ocean for a Liberty type ship. The optimal route is charted using Dijkstra’s algorithm for minimal time path between Calcutta and Sumatra. The optimum track information has broad scope for obtaining a safer route, least time route by avoiding delay in schedule with minimum fuel consumption.     

A comparison of altimeter and gravimetric geoids in the Tonga Trench and Indian Ocean areas

A gravimetric geoid computed using different techniques has been compared to a geoid derived from Geos-3 altimeter data in two 30°×30° areas: one in the Tonga Trench area and one in the Indian Ocean. The specific techniques used were the usual Stokes integration (using 1°×1° mean anomalies) with the Molodenskii truncation procedure; a modified Stokes integration with a modified truncation method; and computations using three sets of potential coefficients including one complete to degree 180. In the Tonga Trench area the standard deviation of the difference between the modified Stokes’ procedure and the altimeter geoid was ±1.1 m while in the Indian Ocean area the difference was ±0.6 m. Similar results were found from the 180×180 potential coefficient field. However, the differences in using the usual Stokes integration procedure were about a factor of two greater as was predicted from an error analysis. We conclude that there is good agreement at the ±1 m level between the two types of geoids. In addition, systematic differences are at the half-meter level. The modified Stokes procedure clearly is superior to the usual Stokes method although the 180×180 solution is of comparable accuracy with the computational effort six times less than the integration procedures.     

印度洋及太平洋海表盐度时空特征分析

目前对印度洋和太平洋海表盐度变化的大尺度分析相对较少，Aquarius作为海表盐度的观测卫星，其观测数据在分析海表盐度时空特征时有着不可替代的优势。为了降低观测资料本身的误差对分析结果的影响，文本首先利用质量—距离双重加权方法生成新的高精度Aquarius网格化月均海表盐度场，并基于此盐度场和Argo资料对2011-09至2015-05印度洋及太平洋海表盐度的时空特征进行了分析。结果显示，盐度分布和纬度有明显的相关性，整体呈现低、高纬偏低，中纬偏高的态势，纬度极值随时间并没有很明显的变化，然而时间最大值随纬度的变化曲线呈现明显的以赤道为中心的近似中心对称分布特征。分析显示印度洋和太平洋盐度分布主要包括4个高盐区和4个低盐区，但每个盐度区的变化趋势与幅度不尽相同。     

Sea Surface Height Variability in the Tropical Indian Ocean: Steric Contribution

Variability of Sea level and its steric contribution in the Tropical Indian Ocean (TIO) was studied based on 15?years (1993?C2007) satellite altimeter observations of sea surface height (SSH) anomaly and steric height (STH) anomaly computed using temperature and salinity fields obtained from Simple Ocean Data Assimilation (SODA) product. Complex Empirical Orthogonal Function (CEOF) analysis was carried out to decompose variability of SSH and STH into various modes to examine the coherency between them. It is revealed that both the parameters exhibit variability in all the time scales. First three major modes of CEOF corresponds to 90% and 84% of the total variability of SSH and STH respectively. There exists strong coherence between the respective CEOF modes of SSH and STH. The first mode of CEOF contributes around ~50% of the total signal corresponds to the annual cycle exhibit large variability in the western Arabian Sea along the Somali and Arabia Coast, latitudinal strip between 2 and 10°N extending from Somali-coast to the west coast of India, coastal oceans around India, and the south eastern TIO. The second CEOF with 25% of total signal contains mixed signature of intra-seasonal and inter-annual periodicities. This exhibit large amplitude in the central south TIO, western and eastern parts of Equatorial Indian Ocean (EIO). Computed long term linear growth rate of sea level anomaly suggests that increase of sea level varies from small (1?C3?mm?yr^?1) in the north TIO to large (8?mm?yr^?1) in the south TIO. Further analysis suggests that SSH trend in the south TIO was mostly governed by steric contribution while the variability of SSH trend in the north TIO could be explained partially by the variability in STH.     

Investigating Effects of Seafloor Topography on Sea Surface Currents in the Caspian Sea and Northern Indian Ocean

Seafloor topography certainly has an impact on ocean circulation in different ways. Due to this assumption, the sea surface currents calculated by optical flow (Horn–Schunck) and geostrophic currents methods are analyzed to observe this impact. Pair of sea surface temperature imageries, calculated sea surface height and sea level anomaly are showed beside depth map in areas with meaningful bathymetric features such as underwater mountains and pools. The reason for the formation of some eddies in the Caspian Sea and Indian Ocean is concluded from the location of pools and knolls. In this study, in addition to introducing new time span for calculating geostrophic currents, Ocean Surface Current Analyses Real-Time (OSCAR) currents are applied to validate our estimated currents. Variety of products such as sea surface temperature imageries, OSCAR currents, depth map, calculated results like sea level anomaly and absolute dynamic topography and estimated currents via optical flow and geostrophic currents have been collected in this paper to make very detailed investigation on depth effect on mentioned water parameters. Results show that impacts of knolls and pools are meaningfully clear in optical flow and geostrophic currents in shaping and rationing water motions.     

A method for monitoring building construction in urban sprawl areas using object-based analysis of Spot 5 images and existing GIS data

Urban sprawl has been identified as one of the most negative effects of global population growth on the environment and biodiversity. Frequent monitoring of urban sprawl is needed to limit the impact of this ongoing phenomenon. This paper proposes precise monitoring of building construction using an object-based classification methodology applied to Spot 5 images with a 2.5 m resolution. An application at a regional scale on Reunion Island in the Indian Ocean shows that this building extraction methodology has limitations in the production of reference urban maps because of difficulties in defining the shape and the number of buildings compared to classical photo-interpretation of aerial photography. However, these results are of great value for planning in urban sprawl areas where up-to-date information is lacking because of the rapid pace of house construction and residential development.     

Observation of mesoscale ocean currents from GEOSAT altimeter data

This paper discusses an altimeter data processing technique designed to compute time series of the mesoscale dynamic sea surface and to produce mean sea surfaces and surface variability. The technique has been applied to Geosat data collected over the North and South Atlantic and the South Indian Ocean. The computed mean sea surfaces show a high correlation with ocean bottom topography, whereas the variability is found to be associated with mesoscale ocean currents. High variability levels are spotted near the Gulfstream Extension and the Agulhas Return Current.Detailed examination of the sea surface and related flow field time series made it possible to identify a large number of eddies and to keep track of them in both the nort-west and south-east Atlantic. Additionally, some of the eddy characteristics have been resolved such as translation and swirl velocity. It is found that the eddy motion is affected by ocean bottom slopes.     

SYSTEMS MAPPING OF THE PHYSICAL-GEOGRAPHIC PROCESS IN A MARINE ENVIRONMENT

An analog to the (terrestrial) physical-geographical process, the concept of boundary surfaces, is elaborated and developed quantitatively for analyzing the diversity of marine ecosystems. Interactions among physical-chemical components of the oceans, and the adjacent coastal, atmospheric, and ocean bottom environments, provides a model used in the study and mapping of heterogeneous “waterscapes.” A series of tables identifies interacting geographic features commonly used as indices for mapping. Sample maps prepared for the Barents Sea and Indian Ocean demonstrate possible results of a systems approach. Translated from: Izvestiya, Vsesoyuznogo geograficheskogo obshchestva, 1985, No. 3, pp. 201-208.