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91.
方法,相干目标分析是利用时间序列多景影像获取地表稳定反射体——高相干点目标的新方法.实验区选择上海市主城区约100 km2 区域,InSAR的实验数据采用覆盖1992~2000年间的25景ERS-1/2的单视复影像.在无先验沉降场模型的情况下,实验结果显示该实验区的地面沉降场在时间范围上跨越8年,平均观测时间采样率约为4个月,垂直形变精度优于5 mm,满足我国对城市地面沉降形变观测的要求.研究结果表明该方法可以用于今后大时间/空间尺度上的高精度地表形变观测. 相似文献
92.
A numerical model (two horizontal dimensions, vertically integrated) is used to investigate the generation of long ocean waves, ranging from 20 min to almost 2 h, at Buenos Aires continental shelf. The domain includes the Río de la Plata estuary and the continental shelf together and extends from 33.5° to 40.5°S latitude, and from 51° to 63°W longitude. Sea-level oscillations are modeled by forcing with passage of atmospheric cold fronts and atmospheric gravity waves. Both forcing mechanisms, which have been present during high activity lapses of long ocean waves, are mathematically implemented. After several numerical simulations, it is concluded that the pressure and wind fields associated to cold fronts do not generate long ocean waves in the area, though they do produce disturbances with periods longer than the tidal ones. On the other hand, it is so concluded that atmospheric gravity waves are an effective mechanism to force long ocean waves. Results obtained show that generation of long ocean waves is highly sensitive depending on the propagation direction and the phase speed of the atmospheric gravity waves. The long ocean wave event detected during the large-amplitude gravity-wave event of 13 October 1985 is successfully simulated. Finally, all our results suggest that atmospheric gravity waves are a highly effective mechanism forcing for the generation of long ocean waves in Buenos Aires coastal waters. 相似文献
93.
J. Höpfner 《Journal of Geodesy》2001,75(2-3):137-150
The annual and semiannual residuals derived in the axial angular momentum budget of the solid Earth–atmosphere system reflect
significant signals. They must be caused by further excitation sources. Since, in particular, the contribution for the wind
term from the atmospheric layer between the 10 and 0.3 hPa levels to the seasonal variations in length of day (LOD) is still
missing, it is necessary to extend the top level into the upper stratosphere up to 0.3 hPa. Under the conservation of the
total angular momentum of the entire Earth, variations in the oceanic angular momentum (OAM) and the hydrological angular
momentum (HAM) are further significant excitation sources at seasonal time scales. Focusing on other contributions to the
Earth's axial angular momentum budget, the following data are used in this study: axial atmospheric angular momentum (AAM)
data derived for the 10–0.3 hPa layer from 1991 to 1997 for computing the missing wind effects; axial OAM functions as generated
by oceanic general circulation models (GCMs), namely for the ECHAM3 and the MICOM models, available from 1975 to 1994 and
from 1992 to 1994, respectively, for computing the oceanic contributions to LOD changes, and, concerning the HAM variations,
the seasonal estimates of the hydrological contribution as derived by Chao and O'Connor [(1988) Geophys J 94: 263–270]. Using
vector representation, it is shown that the vectors achieve a close balance in the global axial angular momentum budget within
the estimated uncertainties of the momentum quantities on seasonal time scales.
Received: 6 April 2000 / Accepted: 13 December 2000 相似文献
94.
L. E. Sjöberg 《Journal of Geodesy》2001,75(5-6):283-290
The topographic and atmospheric effects of gravimetric geoid determination by the modified Stokes formula, which combines
terrestrial gravity and a global geopotential model, are presented. Special emphasis is given to the zero- and first-degree
effects. The normal potential is defined in the traditional way, such that the disturbing potential in the exterior of the
masses contains no zero- and first-degree harmonics. In contrast, it is shown that, as a result of the topographic masses,
the gravimetric geoid includes such harmonics of the order of several centimetres. In addition, the atmosphere contributes
with a zero-degree harmonic of magnitude within 1 cm.
Received: 5 November 1999 / Accepted: 22 January 2001 相似文献
95.
强弱南海夏季风活动及大气季节内振荡 总被引:26,自引:0,他引:26
应用NCEP再分析资料和中国降水资料,分析研究了对应南海强、弱夏季风的环流形势及其与之相应的中国东部的降水异常。其结果表明,由强、弱夏季风所引起的中国气候异常是完全不同(甚至反相)的。分析大气季节内振荡(ISO)的活动还表明,对应大气强(弱)南海夏季风,南海地区 850 hPa也有强(弱)大气 ISO;而强、弱南海夏季风环流(200 hPa和 850 hPa)主要由异常的大气ISO所激发。本研究还揭示了南海地区大气ISO的变化往往与江淮地区大气ISO的变化反相,例如南海地区的强(弱)大气ISO常与江淮流域的弱(强)大气ISO相对应。对于大气ISO的强度,一般多表现出局地激发特征,经向传播相对较弱。 相似文献
96.
97.
Analysis And Simulation Of Surface-Layer Winds Using Multiplicative Cascade Models With Self-Similar Probability Densities 总被引:1,自引:0,他引:1
Statistical analysis techniques based on multiplicative cascades are investigated for use with surface-layer wind data sets collected in the atmospheric boundary layer over flat farm land. The data were found to exhibit multiscaling statistics, allowing the surface-layer winds to be simulated with the use of multiplicative random cascades. The study found evidence that, for the surface-layer at least, these cascade models (andhence the methods of multifractal analysis) should be applied in separate ways to the microscale inertial range, and the mesoscale. This is at odds with the view found in the existing literature, which proposes a `universal multifractal' model to replace the widely held view that there exists separate microscale, mesoscale and synoptic scales for which the processes governing each are different. At least two separate ranges of scaling are suggested for surface-layer wind data, corresponding to the microscale inertial range and the mesoscale. For the case of the mesoscale range, a self-similar distribution of weighting factors was found for the wind speed data themselves, rather than for an intermediate (dissipation) field, as is required for themicroscale data. 相似文献
98.
R. V. Rohli A. J. Vega M. R. Binkley S. D. Britton H. E. Heckman J. M. Jenkins Y. Ono D. E. Sheeler 《Applied geography (Sevenoaks, England)》2001,21(4)
Impacts on water resources caused by human activity, natural climate variation and long-term climate change are unclear in the US Great Lakes region. Improved understanding of the impact of atmospheric circulation on stream discharge variability into the Lakes is thus important. In this analysis, monthly surface and mid-tropospheric circulation patterns suggest that surface pressure variations over Missouri and Illinois are most strongly correlated to discharge. The mid-tropospheric patterns most directly related to discharge place the Great Lakes in a trough-to-ridge flow pattern. The analysis confirms that at this scale, lee shore advection resulting in ‘lake-effect’ precipitation is not very important to regional discharge, and neither are variations in the Pacific–North American teleconnection. 相似文献
99.
单波高精度测距系统的研究 总被引:12,自引:0,他引:12
本文介绍了测距精度优于10^-6的自动高精度测距系统的构成、原理及春应用。 相似文献
100.