共查询到20条相似文献，搜索用时 15 毫秒
1.
Heikki Virtanen 《Journal of Geodynamics》2004,38(3-5):407
Loading by atmosphere and by the Baltic Sea cause gravity change at Metsähovi, located 15 km from the open sea. Gravity is changed by both the Newtonian attraction of the loading mass and by the crustal deformation. We have performed loading calculations using appropriate Green's function for both gravity and deformation, for both atmospheric and Baltic loading. The loading by atmosphere has been computed using a detailed surface pressure field from high resolution limited area model (HIRLAM) for north Europe up to 10° distances. Baltic Sea level is modelled using tide gauge records. Calculations show that 1 m of uniform layer of water corresponds to 31 nm s−2 in gravity and −11 mm in height. Modelled loading is compared with observations of the superconducting gravimeter T020 for years 1994–2002. The combination of HIRLAM and a tide gauge record decreases RMS of gravity residuals by 14% compared to single admittance in air pressure corrections without sea level data. Regression of gravity residuals on the tide gauge record at Helsinki (at 30 km distance) gives a gravity effect of 26 nm s−2 m−1 for Baltic loading.The gravity station is co-located with a permanent GPS station. We have also associated the loading effects of the atmosphere and of the Baltic Sea with temporal height variations. The range of modelled vertical motion due to air pressure was 46 mm and that due to sea level 18 mm. The total range was 38 mm. The effects of the Baltic Sea and of the atmosphere partly cancel each other, since at longer periods the inverse barometer assumption is valid. Regression of the modelled height on local air pressure gives −0.37 mm hPa−1, corresponding approximately to width 6° for pressure system.We have tested the models using one year of daily GPS data. Multilinear regression on local air pressure and sea level in Helsinki gives the coefficient −0.34 mm hPa−1 for pressure, and −11 mm m−1 for sea level. These match model values. Loading by air pressure and Baltic Sea explains nearly 40% of the variance of daily GPS height solutions. 相似文献
2.
热带气旋能在短期内造成海水和大气质量的重新分布,使得近海地表受力发生变化,进而产生非潮汐负荷形变,对现今高精度大地测量的影响已不容忽视.为了保证空间大地测量结果的精度和稳定性,热带气旋引起的地表形变必须进行有效的估计.因此本文联合NOS、GLOSS验潮站数据与海潮模型,通过获取非潮汐残余量分析了热带气旋“MATTHEW”引起的风暴潮.利用ECCO海洋环流模型、ERAin大气再分析模型、HUGO-m海洋动力学模型,分别估计了“MATTHEW”引起非潮汐海洋负荷、非潮汐大气负荷、动力学响应下非潮汐海洋负荷对地表位移的影响,结果表明热带气旋影响下的广大区域地表都不同程度受到非潮汐负荷的作用,最大位移分别达到-9.13 mm、3.31 mm、-6.11 mm,并且加入动力学响应的非潮汐海洋负荷要普遍大于IB(Inverted Barometer)响应下的结果.在对比不同位置站点所受负荷差异时,发现“大陆站”非潮汐海洋负荷形变普遍大于“岛屿站”,而“岛屿站”更易受非潮汐大气负荷的影响. 相似文献
3.
Carla Braitenberg Patrizia MarianiLavinia Tunini Barbara GrilloIldikò Nagy 《Journal of Geodynamics》2011
Our goal is to determine vertical crustal movement rates from tide gauge and satellite altimetry measurements. Tide gauges measure sea level, but as they are fixed to the crust, they sense both sea surface height variations and vertical crustal movements. The differential sea level rates of sufficiently nearby stations are a good means to determine differential crustal movement rates, when sea level height variations can be assumed to be homogeneous. Satellite altimetric measurements determine sea surface height variations directly and can be used to separate the crustal signal from the sea surface height variations in tide gauge measurements. The correction of the tide gauge sea level rates for the sea surface height contribution requires collocation of the satellite pass and the tide gauge station. We show that even if this is not the case, the satellite altimetric observations enable correction of differential tide gauge rates for the effects of sea surface rate inhomogeneities. 相似文献
4.
利用弹性地球负荷理论和流体静力学平衡假设条件下的干空气及其垂直温度梯度分布,理论计算了大气压力作用下地表位移、重力和倾斜格林函数．详细讨论了不同地球模型、台站高程、周边地形、地表大气温度和水汽含量等因素对计算结果的影响．数值结果说明大气效应弹性项影响主要来自于远离台站的区域;引力项对重力的影响主要贡献来自于台站近区,对倾斜的影响来自于远离台站的区域．各种因素对大气重力和倾斜格林函数的影响分别在01°和1°角距范围内,但其综合影响较为复杂． 相似文献
5.
A high-resolution, regional coupled atmosphere–ocean model is used to investigate strong air–sea interactions during a rapidly developing extratropical cyclone (ETC) off the east coast of the USA. In this two-way coupled system, surface momentum and heat fluxes derived from the Weather Research and Forecasting model and sea surface temperature (SST) from the Regional Ocean Modeling System are exchanged via the Model Coupling Toolkit. Comparisons are made between the modeled and observed wind velocity, sea level pressure, 10 m air temperature, and sea surface temperature time series, as well as a comparison between the model and one glider transect. Vertical profiles of modeled air temperature and winds in the marine atmospheric boundary layer and temperature variations in the upper ocean during a 3-day storm period are examined at various cross-shelf transects along the eastern seaboard. It is found that the air–sea interactions near the Gulf Stream are important for generating and sustaining the ETC. In particular, locally enhanced winds over a warm sea (relative to the land temperature) induce large surface heat fluxes which cool the upper ocean by up to 2 °C, mainly during the cold air outbreak period after the storm passage. Detailed heat budget analyses show the ocean-to-atmosphere heat flux dominates the upper ocean heat content variations. Results clearly show that dynamic air–sea interactions affecting momentum and buoyancy flux exchanges in ETCs need to be resolved accurately in a coupled atmosphere–ocean modeling framework. 相似文献
6.
With the long-term goal of developing an operational forecast system for total water level, we conduct a hindcast study of global storm surges for Fall 2014 using a baroclinic ocean model based on the NEMO framework. The model has 19 vertical levels, a horizontal resolution of 1/12°, and is forced by hourly forecasts of atmospheric wind and air pressure. Our first objective is to evaluate the model’s ability to predict hourly sea levels recorded by a global array of 257 tide gauges. It is shown that the model can provide reasonable predictions of surges for the whole test period at tide gauges with relatively large tidal residuals (i.e., gauges where the standard deviation of observed sea level, after removal of the tide, exceeds 5 cm). Our second objective is to quantify the effect of density stratification on the prediction of global surges. It is found that the inclusion of density stratification increases the overall predictive skill at almost all tide gauges. The increase in skill for the instantaneous peak surge is smaller. The location for which the increase in overall skill is largest (east coast of South Africa) is discussed in detail and physical reasons for the improvement are given. 相似文献
7.
《Journal of Geodynamics》2010,49(3-5):348-353
In this study, the loading gravity effect of air mass changes calculated with the three-dimension (3D) meteorological data from the European Centre for Medium-range Weather Forecasts (ECMWF) are removed from superconducting gravimeter (SG) observations. The global hydrological gravity effect is computed and removed with hydrological data from the Global Land Data Assimilation System (GLDAS). Otherwise, the gravity influences induced by a theoretical self-consistent ocean pole tide and variations in length of day (LOD) are considered in the calculation. After removing the influences mentioned previously and also considering the long term trend in the data, a very nice linear relationship between the theoretical gravity pole tide and observed gravity residual (containing the observed gravity pole tide) for each of the selected 9 GGP stations we considered can be obtained. Therefore, the gravimetric factor of the gravity pole tide can be estimated with a simple linear regression. The results show that no clear phase lag is found between the theoretical gravity pole tide and observed gravity residuals from the nine SG stations. 相似文献
8.
重力测量中需要扣除大气的影响.大气负荷对重力测量的影响可以分为大气质量变化引起的直接效应和大气负荷引起的地球变形带来的间接效应,大气负荷对重力观测值的直接影响,相对于间接效应量级较大.本文从理论上研究了大气负荷对重力观测的直接影响,仿照Farrell定义的负荷格林函数,引入大气重力格林函数,用来表示大气压变化对于重力观测的直接引力影响.在前人的基础上,本文采用了更为精细的大气模型,考虑大气温度随高程的变化,用离散褶积的方法求得了大气重力格林函数的理论值.实际计算时还要考虑地表温度、台站高程、周围地形等因素的影响,本文讨论了这些因素对大气重力格林函数的影响.考虑地表温度、台站高程、地形改正等各种影响因素以及地球变形引起的间接效应后,对台站周围区域积分即可求得大气变化引起的理论重力信号. 相似文献
9.
《Continental Shelf Research》2007,27(10-11):1548-1567
A two-way nested coupled tide-surge prediction model was established and applied in the Taiwan Strait and adjacent sea area in this study. This two-dimensional (2D) model had a fine horizontal resolution and took into account the interaction between storm surges and astronomical tides, which made it suitable for depicting the complicated physical properties of storm surges in the Taiwan Strait. A two-way nesting technique and an open boundary condition developed from Flather's radiation condition and Røed and Smedstad's local mode idea, were successfully implemented in the model. A simulation experiment showed that the open boundary condition could be used in the coupled tide-surge model and that the performance of the two-way nested model was slightly superior in accuracy to that of the one-way nested one.The fluctuations of storm surge residuals with tidal period at Sansha and Pingtan tide stations during the period of typhoon Dan in 1999 were well reproduced by the model, with the coupling effect between storm surges and tides indicating that the effect of astronomical tides upon typhoon surges should be considered in a storm-surge prediction model for the Taiwan Strait. The forecast experiment during typhoon Talim in 2005 showed that the storm surge prediction outputs by the model were better in the early 20 h of the forecast period of each model run than those in the later period due to the prediction accuracy of the typhoon track, maximum winds, and central air pressures. 相似文献
10.
介绍了在香港地区重力固体潮合作观测成果, 获得了该地区完整的重力固体潮实测模型. 利用全球和近海海潮模型以及岛屿验潮站数据较系统地研究了海潮负荷特征, 反演了全球海潮模型的适定性. 数值结果说明周日频段内的海潮模型要比半日频段内的模型更加稳定, 实施验潮站潮位高变化改正对精密确定重力固体潮相位滞后起重要作用. 文章还研究了重力观测残差和台站背景噪声水平. 本项研究填补了中国地壳运动观测网络在该地区重力固体潮观测空白, 为地表和空间大地测量提供有效参考和服务. 相似文献
11.
Daily sea level variability in the Adriatic Sea is studied from different data sets using Empirical Orthogonal Functions, in connection with atmospheric pressure and wind stress. The first mode explains 56–69% of total variance and consists of uniform sea level variability all over the basin, correlated with atmospheric pressure through the inverse barometer effect. The second mode explains 13–16% of variance and accounts for an along-basin sea level gradient, which is correlated with the meridional wind stress component. The first two Principal Components are used as proxies to pressure- and wind-induced components of storm surges in the northern Adriatic. The analysis of the frequency of the most intense events in the 1957–2005 period shows that the wind contribution to storm surges has decreased, while no significant trends are found in the contribution of atmospheric pressure. 相似文献
12.
连续重力观测和GPS的技术结合能够监测到物质迁移和地壳垂直形变之间的量化关系.和相对重力测量以及绝对重力测量技术相比,其避免了时间分辨率和观测精度低,无法精细描述观测周期内的物质迁移过程问题.本文利用武汉九峰地震台超导重力仪SGC053超过13000 h连续重力观测数据;同址观测的绝对重力仪观测结果;气压数据;周边GPS观测结果;GRACE卫星的时变重力场;全球水储量模型等资料,采用同址观测技术、调和分析法、相关分析方法在扣除九峰地震台潮汐、气压、极移和仪器漂移的基础上,利用重力残差时间序列和GPS垂直位移研究物质迁移和地壳垂直形变之间的量化关系.结果表明:在改正连续重力观测数据的潮汐、气压、极移的影响后,不仅准确观测到2009年的夏秋两季由于水负荷引起的约(6~8)×10-8m·s-2短期的重力变化.而且在扣除2.18×10-8(m·s-2)/a仪器漂移和水负荷的影响后,验证了本地区长短趋势垂直形变和重力变化之间具有一致的负相关性规律.同时长趋势表明该地区地壳处于下沉,重力处于增大过程,增加速率约为1.79×10-8(m·s-2)/a.武汉地区重力梯度关系约为-354×10-8(m·s-2)/m. 相似文献
13.
地震前孕震区弹性参数发生变化,从而导致地震波速变化.本文根据波速异常现象并利用负荷潮汐研究结果,估算了中国沿海某些地区在孕育一次七级地震时 M2负荷潮汐所引起的重力和倾斜的变化.发现重力变化甚微,倾斜变化可观.建议在确定地震重点区的沿海进行一些倾斜潮汐观测. 相似文献
14.
本文利用卫星重力、卫星测高和海洋温盐数据反演计算全球海水质量变化,并分析其时空变化特征.卫星重力数据利用2003年1月~2006年12月的GRACE月时变重力场球谐系数,同时考虑替换一阶项和C20项,并进行了相关误差滤波、高斯滤波和陆地水文信号泄漏改正,计算得到海洋等效水高变化;利用相同时间跨度的卫星测高数据和海洋温度、盐度水文观测数据,计算全球海平面变化和比容海平面变化,反演得到海水质量变化.反演的两种海水质量变化的年际变化特征一致性较好.三种数据得到的长期趋势变化,与1993~2003年的结果相比,可以看出,海水质量变化加速,并已成为全球海平面上升的主要因素. 相似文献
15.
GPS技术能以高空间和高时间分辨率监测地表形变.但由于测量原理的不同,GPS监测的地表形变与GRACE存在差异.本文比较了ITRF2008-GPS残差序列与基于CSR的RL05版本的GRACE球谐系数的地表形变序列的差异.结果表明,GPS和GRACE的周年变化在高程方向上具有较好的一致性,但水平方向的差异明显.重点分析了影响GPS/GRACE地表形变差异(尤其是水平方向)的三个因素:不同GPS站时间序列间的不确定性,热弹性形变和区域形变.GPS站地表形变本身的不确定度在一定程度上导致了GPS/GRACE间的差异(特别是水平方向).结合热弹性形变理论指出,由温度变化引起的热弹性形变也是导致GPS/GRACE的南北方向差异的主要原因之一.因此利用GPS数据研究地表质量负载时,必须消除热弹性形变的影响.区域负载对GPS/GRACE水平方向差异的影响也是不可忽略的,特别是对欧洲区域. 相似文献
16.
《Journal of Geodynamics》2010,49(3-5):354-359
In order to achieve a consistent combination of terrestrial and satellite-derived (GRACE) gravity field variations reductions of systematic perturbations must be applied to both data sets. At the same time evidence needs to be provided that these reductions are both necessary and sufficient. Based on the OMCT and the ECCO model the gravity effect of non-tidal oceanic mass shifts is computed for various sites equipped with a superconducting gravimeter (SG) and esp. the long-periodic contributions are studied. With these oceanic models the dynamic ocean response to atmospheric pressure loading is automatically computed, and thus goes beyond the more simplistic concepts of an inverted barometer, or alternately a rigid ocean, which is a clear advantage.The findings so far are ambiguous: for instance the systematic seasonal change of about 10 nm/s2 in gravity for mid-European stations is presently not found in the observed gravity variations. Generally, the order of magnitude of the total effect of 22–27 nm/s2 is surprisingly large for inland stations. In some data sections the reduction leads to the removal of some of the larger residuals. The results obtained for the South-African station Sutherland differ. Here the modelled seasonal variation caused by the non-tidal oceanic mass redistribution and gravity residuals generally correlate, and thus by the reduction an improvement of the signal-to-noise ratio in the gravity observations is achieved.An explanation for the different results might be found in the global hydrological models. Such a model is needed in order to remove the effect of large-scale variations in continental water storage in the gravity observations. This reduction plays a greater role for European stations than for the South African site. A critical impact of the land-sea-mask used in the oceanic models and the subsequent insufficient resolution of the North and Baltic Sea on the computations at the mid-European sites could not be confirmed.From a comparison between the OMCT and the ECCO model substantial discrepancies in some regions of the earth emerge, while both predict variations at inland stations in Europe, South Africa, and Asia of similar magnitude. We currently hesitate to recommend including this reduction in the routine processing of SG data because the seasonal order of magnitude for inland stations is unexpectedly large and partly significant deviations between the modelled oceanic effects exist. If the order of magnitude proves to be correct universally, this reduction has to be applied. 相似文献
17.
Series of gravity recordings at the stations Medicina (Italy) and Wettzell (Germany) are investigated to separate seasonal gravity variations from long-term trends in gravity. The findings are compared to height variations monitored by continuous GPS observations. To study the origin of these variations in height and gravity the environmental parameters at the stations are included in the fact finding. In Medicina, a clear seasonal signal is visible in the gravity and height data series, caused by seasonal fluctuations in the atmosphere including mass redistribution, the ocean, groundwater but also by geo-mechanical effects such as soil consolidation and thermal expansion of the structure supporting the GPS antenna. In Wettzell, no seasonal effect could be clearly identified, and the long-term trend in gravity is mainly caused by ground water variations. The successful combination of height and gravity series with the derived ratio of gravity to height changes indicates that the long-term trends in height and gravity are most likely due to mass changes rather than to tectonic movements. 相似文献
18.
Numerical study of the barotropic responses to a rapidly moving typhoon in the East China Sea 总被引：2，自引：1，他引：1
Yang Ding Huaming Yu Xianwen Bao Liang Kuang Caixia Wang Wenjuan Wang 《Ocean Dynamics》2011,61(9):1237-1259
Barotropic responses of the East China Sea to typhoon KOMPASU are investigated using a high-resolution, three-dimensional,
primitive equation, and finite volume coastal ocean model. Even the fact that the typhoon KOMPASU only brushed across the
brink of China mainland without landing, it still imposed great influence across China's east coastal area, where storm surges
ranging from 35 to 70 cm were intrigued during this event and a large wake of water setdown due to the outward radial transport
driven by the cyclonic wind stress was generated after the KOMPASU traveled across the Yellow Sea. Analysis of the numerical
results reveals that the barotropic waves propagating along the coast after the typhoon's landing can be identified as Kelvin
wave and the currents associated with the storm are geostrophic currents. A series of model runs are initiated to diagnose
the effects of wind stress, atmospheric pressure, and storm track variation on the surge's spatial distribution in the East
China Sea. The barotropic waves affected by the atmospheric disturbance due to the typhoon in deep Pacific Ocean travel far
more rapidly, arriving at the coastal regions at least 60 h ahead of the typhoon. The wave amplitudes are merely 0.2–0.4 cm
and damp gradually due to friction. The model experiments also confirm that the surge levels in nearshore regions are highly
dominated by winds, whereas the water level variations in deeper areas are controlled by the atmospheric pressure forcing
during typhoon events in the East China Sea. 相似文献
19.
GPS坐标时间序列呈现显著的季节性变化,通常认为大气压、非潮汐海洋负载及水文负载(统称为地表质量负载)是引起测站谐波变化的主要因素.本文计算了不同地表质量负载造成的测站位移,以此修正中国区域11个IGS基准站的坐标时间序列.建立了地球物理现象与测站季节性变化及噪声特性之间的初步数值联系,认为其会造成测站的噪声特性变化,主要表现为带通及随机漫步噪声特征,且仅能减小测站U分量的周年运动,但并不是造成测站U分量半周年运动及水平方向周年运动的主要原因.深入分析了造成中国区域IGS基准站非线性变化的其他可能因素,重点探讨了周日(S1)、半周日(S2)大气潮汐对基准站周年振幅的贡献,由此提出S1、S2大气潮汐是造成中国区域IGS基准站周年运动,尤其是中南部测站垂向周年运动的主要因素之一. 相似文献
20.
In this study, we compare simulated storm surges run on the two-dimensional operational storm surge/tide forecast system (regional
tide/storm surge model (RTSM), based on Princeton ocean model) of the Korean Meteorological Administration and the three-dimensional
regional ocean modeling system (ROMS), using observational data from 30 coastal tidal stations of three typhoons that struck
Korea in 2007. A maximum positive bias of 6.8 cm was found for Typhoon Manyi predicted by ROMS, while a maximum negative bias
of −7.4 cm was shown for Typhoon Nari predicted by RTSM. For all three typhoons, the total averaged root mean square error
was 10 cm for the two models. Although the statistical results for the storm surge comparison between the observations and
RTSM predictions were better than those for ROMS, with the exception of Typhoon Nari, the spatial and temporal variations
of ROMS were larger than those of RTSM. 相似文献