共查询到20条相似文献，搜索用时 31 毫秒
1.
Since 1995, the global positioning system (GPS) has been exploited by the means of the radio occultation (RO) method to obtain the vertical profiles of refractivity, temperature, pressure, and water vapor in the neutral atmosphere and electron density in the ionosphere. Applying the RO method to the study of the Earths atmosphere was demonstrated for the first time with the GPS/MET experiment. Since then, several satellites with GPS receivers, suitable for RO experiments, have been launched including Oersted, SUNSAT, CHAMP, SAC-C, and GRACE. Future RO investigations that are planned now include FORMOSAT3/COSMIC and Terra-SAR missions. New elements in the RO technology are required to meet the goals of improving the accuracy and broadening the potential of the RO method. In this paper, a methodological review of RO investigations is presented to emphasize new directions in applying the RO method: measuring the vertical gradients of the refractivity in the atmosphere and electron density in the lower ionosphere, determination of the temperature regime in the upper stratosphere, investigation of the internal wave activity in the atmosphere, and study of the ionospheric disturbances on a global scale. These new directions may be relevant for investigating the relationships between processes in the atmosphere and mesosphere, the study of thermal regimes in the intermediate heights of the upper stratosphere—lower mesosphere, and the analysis of the influence of the space weather phenomena on the lower ionosphere. 相似文献
2.
We show that the amplitude of the Global Positioning System (GPS) signals in the radio occultation (RO) experiments is an indicator of the activity of the gravity waves (GW) in the atmosphere. The amplitude of the GPS RO signals is more sensitive to the atmospheric wave structures than is the phase. Early investigations used only the phase of the GPS occultation signals for statistical investigation of the GW activity in the height interval 10–40 km on a global scale. In this study, we use the polarization equations and Hilbert transform to find the 1-D GW radio image in the atmosphere by analyzing the amplitude of the RO signal. The radio image, also called the GW portrait, consists of the phase and amplitude of the GW as functions of height. We demonstrate the potential of this method using the amplitude data from GPS/Meteorology (GPS/MET) and satellite mission Challenge Mini-satellite Payload (CHAMP) RO events. The GW activity is nonuniformly distributed with the main contribution associated with the tropopause and the secondary maximums related to the GW breaking regions. Using our method we find the vertical profiles of the horizontal wind perturbations and its vertical gradient associated with the GW influence. The estimated values of the horizontal wind perturbations are in fairly good agreement with radiosonde data. The horizontal wind perturbations v(h) are ±1 to ±5 m s with vertical gradients dv/dh ±0.5 to ±15 m s km at height 10–40 km. The height dependence of the GW vertical wavelength was inferred through the differentiation of the GW phase. Analysis of this dependence using the dispersion relationship for the GW gives the estimation of the projection of the horizontal background wind velocity on the direction of the GW propagation. For the event considered, the magnitude of this projection changes between 1.5 and 10 m s at heights of 10–40 km. We conclude that the amplitude of the GPS occultation signals contain important information about the wave processes in the atmosphere on a global scale. 相似文献
3.
A. G. Pavelyev J. Wickert Y. A. Liou Ch. Reigber T. Schmidt K. Igarashi A. A. Pavelyev S. S. Matyugov 《GPS Solutions》2005,9(2):96-104
A local mechanism for strong ionospheric effects on radio occultation (RO) global positioning satellite system (GPS) signals is described. Peculiar zones centered at the critical points (the tangent points) in the ionosphere, where the gradient of the electron density is perpendicular to the RO ray trajectory, strongly influence the amplitude and phase of RO signals. It follows from the analytical model of local ionospheric effects that the positions of the critical points depend on the RO geometry and the structure of the ionospheric disturbances. Centers of strong ionospheric influence on RO signals can exist, for example, in the sporadic E-layers, which are inclined by 3–6° relative to the local horizontal direction. Also, intense F2 layer irregularities can contribute to the RO signal variations. A classification of the ionospheric influence on the GPS RO signals is introduced using the amplitude data, which indicates different mechanisms (local, diffraction, etc.) for radio waves propagation. The existence of regular mechanisms (e.g., local mechanism) indicates a potential for separating the regular and random parts in the ionospheric influence on the RO signals. 相似文献
4.
Based on 40 years of radio-occultation (RO) experiments, it is now recognized that the phase acceleration of radio waves (equal
to the time derivative of the Doppler shift), derived from analysis of high-stability Global Positioning System (GPS) RO signals,
is as important as the Doppler frequency. The phase acceleration technique allows one to convert the phase and Doppler frequency
changes into refractive attenuation variations. From such derived refractive attenuation and amplitude data, one can estimate
the integral absorption of radio waves. This is important for future RO missions when measuring water vapor and minor atmospheric
gas constituents, because the difficulty of removing the refractive attenuation effect from the amplitude data can be avoided.
The phase acceleration technique can be applied also for determining the location and inclination of sharp layered plasma
structures (including sporadic E
s layers) in the ionosphere. The advantages of the phase acceleration technique are validated by analyzing RO data from the
Challenging Minisatellite Payload (CHAMP) and the FORMOSA Satellite Constellation Observing Systems for Meteorology, Ionosphere,
and Climate missions (FORMOSAT-3/COSMIC). 相似文献
5.
A study of the impact of FORMOSAT-3/COSMIC GPS radio occultation (RO) and dropwindsonde data on regional model simulations
for a 11-day period during the 2007 Mei-yu season is presented. The Weather Research and Forecasting (WRF) model and its three-dimensional
variation component, WRF-Var, are used for regional model predictions of heavy rainfall events in Taiwan. Without the use
of GPS RO and dropwindsonde data, pressure and relative humidity are, in general, underestimated by the model; temperature
predictions have a warm bias at the low level and a cold bias at the high level; and the east–west and north–south component
winds have positive and negative biases, respectively. Incorporating GPS RO data tends to improve the prediction for longer
integration. The assimilation of dropwindsonde data improves the forecast at the earlier time and at higher levels, and the
improvement decreases over time. The reason the dropwindsonde data produce a positive impact earlier and the GPS RO data later
is that there are few GPS RO observations in the fine domain. The large-scale simulation is first improved using the GPS RO
observations, and the resulting changes can have a positive impact on the mesoscale at the later time. The dropwindsonde observations
were taken inside the fine domain such that their impact can be detected early in the simulation. With both types of observation
included, the prediction shows even greater improvement. At the earlier forecast time, there is nearly no impact from GPS
and dropwindsonde data on rainfall forecasts. However, at the later integration time, the GPS data start to significantly
improve the rainfall forecast. The dropwindsonde data also provide a positive impact on rainfall forecasts, but it is not
as significant as that of the GPS data. 相似文献
6.
Use of the L2C signal for inversions of GPS radio occultation data in the neutral atmosphere 总被引：1，自引：0，他引：1
S. V. Sokolovskiy W. S. Schreiner Z. Zeng D. C. Hunt Y.-H. Kuo T. K. Meehan T. W. Stecheson A. J. Mannucci C. O. Ao 《GPS Solutions》2014,18(3):405-416
Results from processing FORMOSAT-3/COSMIC radio occultations (RO) with the new GPS L2C signal acquired both in phase locked loop (PLL) and open loop (OL) modes are presented. Analysis of L2P, L2C, and L1CA signals acquired in PLL mode shows that in the presence of strong ionospheric scintillation not only L2P tracking, but also L1CA tracking often fails, while L2C tracking is most stable. The use of L2C improves current RO processing in the neutral atmosphere mainly by increasing the number of processed occultations (due to significant reduction in the number of L2 tracking failures) and marginally by a reduction in noise in statistics. The latter is due to the combination of reduced L2C noise (compared to L2P) and increased L1CA noise in those occultations where L2P would have failed. This result suggests application of OL tracking for L1CA and L2C signals throughout an entire occultation to optimally acquire RO data. Two methods of concurrent processing of L1CA and L2C RO signals are considered. Based on testing of individual occultations, these methods allow: (1) reduction in uncertainty of bending angles retrieved by wave optics in the lower troposphere and (2) reduction in small-scale residual errors of the ionospheric correction in the stratosphere. 相似文献
7.
近年来伴随导航定位技术与无线电掩星技术的结合，一种崭新的遥感地球大气的方法-Global Positioning System/Meteoroloby(GPS/NET)应运而生，该方法可以有效地探测大气温、压、湿等气象参数。本文在介绍利用GPS-LEO掩星技术探测地球大气的原理，以及反演大气参数的方法、步骤的基础上，给出了模拟掩星数据反演出的温度廓线、密度廓线及部分GPS/NET实验数据的初步反演结果。通过分析可以看出，利用掩星技术反演出的温度廓线与大气实际情况相符，并且与ECMWF、NCEP的结果吻合较好。在干空气假设条件下，近地面大气的反演结果与实际情况还存在一定误差，有待深入研究解决。 相似文献
8.
2013年中国发射了首颗进行全球导航卫星系统(global navigation satellite system,GNSS)掩星观测的气象卫星风云3号C星(Fengyun-3C,FY-3C),且已发布自2014年6月以来的FY-3C掩星大气产品,但目前还未见将其应用于大气边界层的相关研究。首次尝试利用FY-3C折射率产品确定边界层高度并进一步进行空间分布分析。结果表明,在小波协方差变换法基础上,进行尖锐度约束,能够确定FY-3C掩星低层大气折射率廓线中可能存在的突变,反演边界层高度。所得到的2015―2018年各年边界层高度全球分布在不同纬度及海洋和陆地上的差异基本体现了边界层与地表气候及地形的关系,但FY-3C折射率产品在低层大气的精度和垂直分辨率相对较低。因此,反演成功率总体上较低,反演结果对边界层高度空间分布细节特征的呈现仍有待提升。 相似文献
9.
多传感器与道路网数据用于汽车导航的研究 总被引：4，自引：0，他引：4
对车载导航系统中GPS接收机，车论计数器和电子罗盘传感器数据与导航电子地图所提供的道路网络数据进行了综合处理，建立了道路网络数据的网络拓扑关系，在此基础上提出了基于道路网络拓扑关系，利用GPS接收机，车轮计数器和电子罗盘传感器对汽车进行实时定位的算法。最后，对导航中汽车的定位误差进行了分析。实验证明，GPS接收机，车轮计数器和电子罗盘传感器与道路网络数据综合，在导航过程中能够补偿GPS信号技失，实时、高精度、高可靠性地确定汽车的位置。 相似文献
10.
车辆导航已成为交通领域一个研究热点。利用GPS导航系统可以获取良好的导航定位精度，但是GPS信号在城市大密度的建筑群中容易被遮挡，从而影响车辆导航过程。而DR系统虽能持续地提供服务，但是其精度随时间变差，从而无法取得良好效果。利用切比雪夫拟合方法，在GPS卫星信号失锁情况下，对DR数据进行拟合处理，并把处理结果与未失锁情况下的GPS导航数据进行比较，验证切比雪夫拟合效果。 相似文献
11.
Vertical deformations from homogeneously processed GRACE and global GPS long-term series 总被引：3，自引：1，他引：2
Volker Tesmer Peter Steigenberger Tonie van Dam Torsten Mayer-Gürr 《Journal of Geodesy》2011,85(5):291-310
Temporal variations in the geographic distribution of surface mass cause surface displacements. Surface displacements derived
from GRACE gravity field coefficient time series also should be observed in GPS coordinate time series, if both time series
are sufficiently free of systematic errors. A successful validation can be an important contribution to climate change research,
as the biggest contributors to mass variability in the system Earth include the movement of oceanic, atmospheric, and continental
water and ice. In our analysis, we find that if the signals are larger than their precision, both geodetic sensor systems
see common signals for almost all the 115 stations surveyed. Almost 80% of the stations have their signal WRMS decreased,
when we subtract monthly GRACE surface displacements from those observed by GPS data. Almost all other stations are on ocean
islands or small peninsulas, where the physically expected loading signals are very small. For a fair comparison, the data
(79 months from September 2002 to April 2009) had to be treated appropriately: the GPS data were completely reprocessed with
state-of-the-art models. We used an objective cluster analysis to identify and eliminate stations, where local effects or
technical artifacts dominated the signals. In addition, it was necessary for both sets of results to be expressed in equivalent
reference frames, meaning that net translations between the GPS and GRACE data sets had to be treated adequately. These data
sets are then compared and statistically analyzed: we determine the stability (precision) of GRACE-derived, monthly vertical
deformation data to be ~1.2 mm, using the data from three GRACE processing centers. We statistically analyze the mean annual
signals, computed from the GPS and GRACE series. There is a detailed discussion of the results for five overall representative
stations, in order to help the reader to link the displayed criteria of similarity to real data. A series of tests were performed
with the goal of explaining the remaining GPS–GRACE residuals. 相似文献
12.
13.
GPS radio occultation measurements on ionospheric electron density from low Earth orbit 总被引：1，自引：0，他引：1
Since the proof-of-concept GPS/Meteorology (GPS/MET) experiment successfully demonstrated active limb sounding of the Earth’s
neutral atmosphere and ionosphere via GPS radio occultation (RO) from low Earth orbit, the developments of electron density
(n
e) retrieval techniques and powerful processing systems have made a significant progress in recent years. In this study, the
researches of n
e profiling from space-based GPS RO observations are briefly reviewed. Applying to the Formosat-3/Constellation Observing System
for Meteorology, Ionosphere and Climate (FS3/COSMIC) data, we also present a compensatory Abel inversion technique including
the effects of large-scale horizontal gradients and/or inhomogeneous ionospheric n
e obtained from an improved near real-time phenomenological model of the TaiWan Ionospheric Model. The results were evaluated
by the ionosonde foF2 and foE data and showed improvements of rms foF2 difference from 29.2 to 16.5% in relative percentage and rms foE difference from 54.2 to 32.7% over the standard Abel inversion. 相似文献
14.
提出了面应变综合预测指标法,目的是将全球卫星定位系统（global position system,GPS）观测结果应用于地震短临预测。基于云南省GPS连续观测资料,利用GPS高精度数据处理软件（GAMIT/GLOBK）处理后获得位移场。对位移场进行网格化插值获得均匀分布于56个网格的位移场,基于每个网格位移场时间序列求取其面应变时间序列,并对每个网格面应变时间序列的映震能力进行评价、综合,提取出适合于云南地区的地震短临异常识别指标。实践表明,综合预测指标对云南地区2011年以来发生的20次5级以上地震进行3个月短临预测,其中准确预测次数为19次,漏报数为1次,虚报5次,认为该指标对地震发震时间、震中均具有较好的指示意义,可用于云南地区未来的地震短临预测实践。 相似文献
15.
GPS/INS navigation precision and its effect on airborne radio occultation retrieval accuracy 总被引：1，自引：1，他引：0
Paytsar Muradyan Jennifer S. Haase Feiqin Xie James L. Garrison Justin Voo 《GPS Solutions》2011,15(3):207-218
An airborne radio occultation (RO) system has been developed to retrieve atmospheric profiles of refractivity, moisture, and temperature. The long-term objective of such a system is deployment on commercial aircraft to increase the quantity of moisture observations in flight corridors in order to improve weather forecast accuracy. However, there are several factors important to operational feasibility that have an impact on the accuracy of the airborne RO results. We investigate the effects of different types of navigation system noise on the precision of the retrieved atmospheric profiles using recordings from the GNSS Instrument System for Multistatic and Occultation Sensing (GISMOS) test flights, which used an Applanix POS/AV 510 Global Positioning System (GPS)/Inertial Navigation System (INS). The data were processed using a carrier phase differential GPS technique, and then the GPS position and inertial measurement unit data were combined in a loosely coupled integrated inertial navigation solution. This study quantifies the velocity precision as a function of distance from GPS reference network sites, the velocity precision with or without an inertial measurement unit, the impact of the quality of the inertial measurement unit, and the compromise in precision resulting from the use of real-time autonomous GPS positioning. We find that using reference stations with baseline lengths of up to 760?km from the survey area has a negligible impact on the retrieved refractivity precision. We also find that only a small bias (less than 0.5% in refractivity) results from the use of an autonomous GPS solution rather than a post-processed differential solution when used in an integrated GPS/INS system. This greatly expands the potential range of an operational airborne radio occultation system, particularly over the oceans, where observations are sparse. 相似文献
16.
基于PDA的森林资源样地调查记录系统的设计与实现 总被引：11，自引：6，他引：5
本文介绍了一种基于PDA并将GPS、MobileGIS等技术进行综合集成的森林资源连续清查样地调查(一类调查)应用系统的设计和实现,并对其系统结构、工作原理、硬件构成、软件设计等进行了论述。该系统将野外调绘和数据采集融为一体,改变了传统的野外调查方式,实现了数据采集自动化,大大提高了外业和内业的工作效率。 相似文献
17.
Metop-GRAS in-orbit instrument performance 总被引：2，自引：1，他引：1
The GRAS instrument on the Metop-A satellite provides more than 600 radio occultation measurement profiles per day. The instrument
is characterized by its wide antenna coverage, high signal-to-noise ratio and an ultra-stable clock reference. The conventional
dual-frequency tracking of GPS signals is under dynamic atmosphere conditions complemented by open loop tracking with sampling
of the signal at a 1 kHz rate, providing an unprecedented view of the signal spectral environment. This paper presents the
instrument performance as derived from analysis of in-orbit measurement data. We show that the noise figure is low enough
to enable mapping of external radio noise variations over the earth’s surface. An error propagation model is presented to
relate instrument characteristics to bending angle performance. This model is also used to illustrate the relation between
filter bandwidth, resolution and measurement noise. The Doppler model, guiding open loop measurements, is found to be accurate
to better than 20 Hz with a possibility for improvement to 10 Hz. The high performance at low altitudes enables the presence
of surface reflections at the −20-dB level to be identified in more than 50% of the occultations. The potential performance
improvements for next generation receivers are discussed. 相似文献
18.
GPS信号相位延迟中包含很多大气信息,通过一定的方法可以从中获取有价值的大气参数。基于地基GPS相位延迟数据,提出了一种结合经验模式的一维变分同化获取大气折射率的方法。利用GPS相位延迟模拟数据进行同化试验,讨论了背景误差的设置对同化结果的影响,采用实测个例对该方法进行了验证。结果表明,该一维变分同化方法可行,并可获取高精度的0~60 km大气折射率。低层大气背景误差设置的准确程度会对整个高度范围内的同化效果产生影响。首次将同化获取的大气折射率应用于无线电波折射修正,取得了很好的修正效果,修正精度可达1 mm量级。 相似文献
19.
Atmospheric modelling in GPS analysis and its effect on the estimated geodetic parameters 总被引：4，自引：2，他引：2
Permanently operating Global Positioning System (GPS) receivers are used today, for example, in precise positioning and determination
of atmospheric water vapour content. The GPS signals are delayed by various gases when traversing the atmosphere. The delay
due to water vapour, the wet delay, is difficult to model using ground surface data and is thus often estimated from the GPS
data. In order to obtain the most accurate results from the GPS processing, a modelling of the horizontal distribution of
the wet delay may be necessary. Through simulations, three such models are evaluated, one of which is developed in this paper.
In the first model the water vapour is assumed to be horizontally stratified, thus the wet delay can be described by only
one zenith parameter. The second model gives the wet delay with one zenith and two horizontal gradient parameters. The third
model uses the correlation between the wet-delay values in different directions. It is found that for large gradients and
strong turbulence the two latter models yield lower errors in the estimated vertical coordinate and wet-delay parameters.
For large gradients this improvement is up to 7 mm in the zenith wet-delay parameter, from 9 mm down to 2 and 4 mm for the
second and third models, respectively.
Received: 7 May 1998 / Accepted: 1 March 1999 相似文献
20.
Estimating the motion of atmospheric water vapor using the Global Positioning System 总被引：1，自引：0，他引：1
Water vapor is both an important component in the atmosphere for the transport of energy and a noise source for space geodetic
observations of the Earth's surface, such as from GPS and interferometric SAR (InSAR) measurements. GPS data collected from
ground receivers are sensitive to the total amount of water vapor above the antenna and data from continuously operating GPS
receivers are routinely used to estimate delays caused by atmospheric water vapor. Using these time series of atmospheric
delay, we have estimated the motion of atmospheric water vapor above GPS networks. The motion above each site is determined
by comparing the time series from different sites and estimating relative time offsets in these time series. These are then
used to determine the velocity field of the atmospheric delays as they move across the network. We have compared the results
with similar estimates inferred from geostationary satellite data and found clear correlation on several occasions. Such results
can be useful for improving the understanding of the energy transport in the atmosphere, the spatial interpolation of water
vapor, and for calibrating InSAR observations for delays caused by water vapor.
Electronic Publication 相似文献