共查询到20条相似文献，搜索用时 687 毫秒
1.
The formation of oil-water emulsion often occurs when oil is spilled into the ocean. Oil weighting factor of oil-water emulsion is one of the most important parameters for emergent oil-spill microwave monitoring. A new method is proposed here to evaluate the oil weighting factor based on fractional Weierstrass scattering model. By using the proposed method, we analyze the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) L-band fully polarimetric data acquired during 2010 Deepwater Horizon oil spill disaster event in the Gulf of Mexico. The result shows that our method performs well in evaluating oil weighting factor of oil-covered area. 相似文献
2.
Estimation of ocean circulation is investigated via assimilation of satellite measurements of the dynamic ocean topography (DOT) into the global finite-element ocean model (FEOM). The DOT was obtained by means of a geodetic approach from carefully cross-calibrated multi-mission altimeter data and GRACE gravity fields. The spectral consistency was achieved by consistently filtering both, the sea surface and the geoid. The filter length is determined by the spatial resolution of the gravity field and corresponds to approximately 241 km half width for the GRACE-based gravity field model ITG-Grace03s.The assimilation of the geodetic DOT was performed by employing a local singular evolutive interpolated Kalman (SEIK) filter in combination with the method of weighting of observations. It is shown that this approach leads to a successful assimilation technique that reduced the RMS difference between the model and the data from 16 cm to 5 cm during one year of assimilation. The ocean model returns an optimized mean dynamic ocean topography. The effects of assimilation on transport estimates across several hydrographic World Ocean Circulation Experiment (WOCE) sections show improvements compared to the FEOM run without data assimilation. As a result of the assimilation, DOT estimates are available in the polar or coastal regions where the geodetic estimates from satellite data alone are not adequate. Furthermore, more realistic features of the ocean can be seen in these areas compared to those obtained using the filtered data fields. 相似文献
3.
本文讨论了海潮对卫星重力测量的影响问题. 首先介绍了海潮对卫星重力测量影响的基本理论；采用FES02和TPXO6海潮模型计算了海潮负荷对卫星重力结果前60阶的影响；并用两个模型之间的差异作为海潮模型精度的估计量，据此计算了海潮模型误差对卫星重力结果的影响. 与GRACE恢复的重力场精度的比较说明：海潮对重力场40阶以下的影响都超过了目前重力场恢复精度；尽管由于卫星测高技术的发展，海潮模型的精度有了很大的提高，但目前的全球海潮模型用于GRACE重力场恢复的前12阶的改正还是不够精确. 另外，我们也利用中国东海和南海潮汐资料以及FES02海潮模型讨论了中国近海潮汐效应对GRACE观测的影响. 结果说明该影响与海潮模型的误差相当. 这反映了当前海潮模型的不确定度，因此通过结合全球验潮站资料有望提高海潮对卫星重力测量的改正精度. 相似文献
4.
A. V. Kuvshinov 《Surveys in Geophysics》2008,29(2):139-186
Electromagnetic induction in the Earth’s interior is an important contributor to the near-Earth magnetic and electric fields.
The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability
in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes:
(a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth’s main
magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these
sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans,
crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling
studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced
by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric
currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling
studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly
(in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral
equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations
both on the ground and at satellite altitudes.
On leave from Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Russian Academy of Sciences, 142190
Troitsk, Moscow region, Russia. 相似文献
5.
Jenny A. U. Nilsson Srdjan Dobricic Nadia Pinardi Vincent Taillandier Pierre-Marie Poulain 《Ocean Dynamics》2011,61(10):1475-1490
The Mediterranean Forecasting System (MFS) has been operational for a decade, and is continuously providing forecasts and
analyses for the region. These forecasts comprise local- and basin-scale information of the environmental state of the sea
and can be useful for tracking oil spills and supporting search-and-rescue missions. Data assimilation is a widely used method
to improve the forecast skill of operational models and, in this study, the three-dimensional variational (OceanVar) scheme
has been extended to include Argo float trajectories, with the objective of constraining and ameliorating the numerical output
primarily in terms of the intermediate velocity fields at 350 m depth. When adding new datasets, it is furthermore crucial
to ensure that the extended OceanVar scheme does not decrease the performance of the assimilation of other observations, e.g.,
sea-level anomalies, temperature, and salinity. Numerical experiments were undertaken for a 3-year period (2005–2007), and
it was concluded that the Argo float trajectory assimilation improves the quality of the forecasted trajectories with ~15%,
thus, increasing the realism of the model. Furthermore, the MFS proved to maintain the forecast quality of the sea-surface
height and mass fields after the extended assimilation scheme had been introduced. A comparison between the modeled velocity
fields and independent surface drifter observations suggested that assimilating trajectories at intermediate depth could yield
improved forecasts of the upper ocean currents. 相似文献
6.
Sotillo MG Fanjul EA Castanedo S Abascal AJ Menendez J Emelianov M Olivella R García-Ladona E Ruiz-Villarreal M Conde J Gómez M Conde P Gutierrez AD Medina R 《Marine pollution bulletin》2008,56(4):686-703
The ESEOO Project, launched after the Prestige crisis, has boosted operational oceanography capacities in Spain, creating new operational oceanographic services and increasing synergies between these new operational tools and already existing systems. In consequence, the present preparedness to face an oil-spill crisis is enhanced, significantly improving the operational response regarding ocean, meteorological and oil-spill monitoring and forecasting. A key aspect of this progress has been the agreement between the scientific community and the Spanish Search and Rescue Institution (SASEMAR), significantly favoured within the ESEOO framework. Important achievements of this collaboration are: (1) the design of protocols that at the crisis time provide operational state-of-the-art information, derived from both forecasting and observing systems; (2) the establishment, in case of oil-spill crisis, of a new specialized unit, named USyP, to monitor and forecast the marine oceanographic situation, providing the required met-ocean and oil-spill information for the crisis managers. The oil-spill crisis scenario simulated during the international search and rescue Exercise "Gijón-2006", organized by SASEMAR, represented an excellent opportunity to test the capabilities and the effectiveness of this USyP unit, as well as the protocols established to analyze and transfer information. The results presented in this work illustrate the effectiveness of the operational approach, and constitute an encouraging and improved base to face oil-spill crisis. 相似文献
7.
The coupled ocean–atmosphere–wave–sediment transport (COAWST) model is used to hindcast Hurricane Ivan (2004), an extremely intense tropical cyclone (TC) translating through the Gulf of Mexico. Sensitivity experiments with increasing complexity in ocean–atmosphere–wave coupled exchange processes are performed to assess the impacts of coupling on the predictions of the atmosphere, ocean, and wave environments during the occurrence of a TC. Modest improvement in track but significant improvement in intensity are found when using the fully atmosphere–ocean-wave coupled configuration versus uncoupled (e.g., standalone atmosphere, ocean, or wave) model simulations. Surface wave fields generated in the fully coupled configuration also demonstrates good agreement with in situ buoy measurements. Coupled and uncoupled model-simulated sea surface temperature (SST) fields are compared with both in situ and remote observations. Detailed heat budget analysis reveals that the mixed layer temperature cooling in the deep ocean (on the shelf) is caused primarily by advection (equally by advection and diffusion). 相似文献
8.
International tidal gravity reference values at Wuhan station 总被引：8，自引：0，他引：8
The international tidal gravity reference values at Wuhan station are determined accurately based on the comprehensive analysis
of the tidal gravity observations obtained from 8 instruments. By comparing these with those in the tidal models given by
Dehant (1997) while considering simultaneously (i) the global satellite altimeters tidal data, and (ii) the Schwiderski global
tidal data and the local ones along the coast of China, it is found that the average discrepancy of the amplitude factors
and of the phase differences for four main waves are given as 5.2% and 3.6% and as 0.16° and 0.08° respectively. They are
improved evidently compared to those determined in early stage, indicating the important procedures in improving the Wuhan
international tidal gravity reference values when including the long-series observations obtained with a superconducting gravimeter,
and when considering the influence of the ocean loading and of the nearly daily free wobble of the Earth’s core. 相似文献
9.
V. Yesubabu C. V. Srinivas K. B. R. R. Hariprasad R. Baskaran 《Pure and Applied Geophysics》2014,171(8):2023-2042
In this work, the impact of assimilation of conventional and satellite remote sensing observations (Oceansat-2 winds, MODIS temperature/humidity profiles) is studied on the simulation of two tropical cyclones in the Bay of Bengal region of the Indian Ocean using a three-dimensional variational data assimilation (3DVAR) technique. The Weather Research and Forecasting (WRF)-Advanced Research WRF (ARW) mesoscale model is used to simulate the severe cyclone JAL: 5–8 November 2010 and the very severe cyclone THANE: 27–30 December 2011 with a double nested domain configuration and with a horizontal resolution of 27 × 9 km. Five numerical experiments are conducted for each cyclone. In the control run (CTL) the National Centers for Environmental Prediction global forecast system analysis and forecasts available at 50 km resolution were used for the initial and boundary conditions. In the second (VARAWS), third (VARSCAT), fourth (VARMODIS) and fifth (VARALL) experiments, the conventional surface observations, Oceansat-2 ocean surface wind vectors, temperature and humidity profiles of MODIS, and all observations were respectively used for assimilation. Results indicate meager impact with surface observations, and relatively higher impact with scatterometer wind data in the case of the JAL cyclone, and with MODIS temperature and humidity profiles in the case of THANE for the simulation of intensity and track parameters. These relative impacts are related to the area coverage of scatterometer winds and MODIS profiles in the respective storms, and are confirmed by the overall better results obtained with assimilation of all observations in both the cases. The improvements in track prediction are mainly contributed by the assimilation of scatterometer wind vector data, which reduced errors in the initial position and size of the cyclone vortices. The errors are reduced by 25, 21, 38 % in vector track position, and by 57, 36, 39 % in intensity, at 24, 48, 72 h predictions, respectively, for the two cases using assimilation of all observations. Simulated rainfall estimates indicate that while the assimilation of scatterometer wind data improves the location of the rainfall, the assimilation of MODIS profiles produces a realistic pattern and amount of rainfall, close to the observational estimates. 相似文献
10.
Hurricanes produce mixing and flow divergences (and convergences) that alter the upper-ocean heat content (OHC), which in turn affects the storm. Ocean observations under a hurricane are rare, making it difficult to validate forecast models. Past research have mainly focused on OHC-changes by vertical mixing and tacitly assumed that horizontal transports are slowly varying. Moreover, effects of coastal boundaries on ocean responses to hurricanes are generally omitted. This work uses satellite data to detect and verify forecast isopycnal motions under hurricane Wilma (Oct/16–26/2005) in the Caribbean Sea and the Gulf of Mexico. The model is then used to show that Wilma-induced convergences in northwestern Caribbean Sea produce increased Yucatan-Channel transport into the Gulf ahead of the storm, and the Yucatan–Loop Current front diverts most of this heat around the Loop. This response is distinct from that of an ocean without the Loop, for which warming is widespread north of the channel. These intricate ocean responses can impact hurricane predictions. 相似文献
11.
Mechanical recovery of oil by oil sorbents is one of the most important countermeasures in marine oil-spill response. Polypropylene is the ideal material for marine oil-spill recovery due to its low density, low water uptake and excellent physical and chemical resistance. Different forms of polypropylene nonwoven sorbents were evaluated in this study in terms of initial oil-sorption capacities and oil-retention properties. The investigation revealed that the fibre diameter, sorbent porosity and oil property are the most important factors in the oil-sorption performance of polypropylene nonwoven sorbents. 相似文献
12.
Junoy J Castellanos C Viéitez JM de la Huz MR Lastra M 《Marine pollution bulletin》2005,50(5):526-536
Eighteen sandy beaches were sampled along the 1659 km of the Galician coast (NW Spain) six months after the Prestige oil-spill to study the impact of the fuel and the clean-up activities on the macroinfauna community. A transect was extended at each beach, from above the drift line to below the swash line at five sampled levels; at each level six 0.05 m2 replicates were taken to a depth of 30 cm and sieved through a 1mm mesh, and the organisms collected and preserved. Results were compared with previous data obtained using the same procedures. The macroinfauna was numerically dominated by the amphipod Pontocrates arenarius, the isopod genus Eurydice, the polychaete Scolelepis squamata, and the amphipod Talitrus saltator. As a result of the Prestige oil-spill and the clean-up activities, beach populations were reduced, with Eurydice and S. squamata as the most affected taxa. 相似文献
13.
This contribution investigates two different ways for mitigating the aliasing errors in ocean tides. This is done, on the one hand, by sampling the satellite observations in another direction using the pendulum satellite mission configuration. On the other hand, a mitigation of the temporal aliasing errors in the ocean tides can be achieved by using a suitable repeat period of the sub-satellite tracks.The findings show, firstly, that it is very beneficial for minimizing the aliasing errors in ocean tides to use pendulum configuration; secondly, optimizing the orbital parameter to get shorter repeat orbit mode can be effective in minimizing the aliasing errors. This paper recommends the pendulum as a candidate for future gravity mission to be launched in longer repeating orbit mode with shorter “sub-cycle” repeat periods to improve the temporal resolution of the satellite mission. 相似文献
14.
Nicolas Reul Severine Fournier Jaqueline Boutin Olga Hernandez Christophe Maes Bertrand Chapron Gaël Alory Yves Quilfen Joseph Tenerelli Simmon Morisset Yann Kerr Susanne Mecklenburg Steven Delwart 《Surveys in Geophysics》2014,35(3):681-722
While it is well known that the ocean is one of the most important component of the climate system, with a heat capacity 1,100 times greater than the atmosphere, the ocean is also the primary reservoir for freshwater transport to the atmosphere and largest component of the global water cycle. Two new satellite sensors, the ESA Soil Moisture and Ocean Salinity (SMOS) and the NASA Aquarius SAC-D missions, are now providing the first space-borne measurements of the sea surface salinity (SSS). In this paper, we present examples demonstrating how SMOS-derived SSS data are being used to better characterize key land–ocean and atmosphere–ocean interaction processes that occur within the marine hydrological cycle. In particular, SMOS with its ocean mapping capability provides observations across the world’s largest tropical ocean fresh pool regions, and we discuss from intraseasonal to interannual precipitation impacts as well as large-scale river runoff from the Amazon–Orinoco and Congo rivers and its offshore advection. Synergistic multi-satellite analyses of these new surface salinity data sets combined with sea surface temperature, dynamical height and currents from altimetry, surface wind, ocean color, rainfall estimates, and in situ observations are shown to yield new freshwater budget insight. Finally, SSS observations from the SMOS and Aquarius/SAC-D sensors are combined to examine the response of the upper ocean to tropical cyclone passage including the potential role that a freshwater-induced upper ocean barrier layer may play in modulating surface cooling and enthalpy flux in tropical cyclone track regions. 相似文献
15.
The value of coupled assimilation is discussed using an intermediate coupled model in which the wind stress is the only atmospheric state which is slavery to model sea surface temperature (SST). In the coupled assimilation analysis, based on the coupled wind–ocean state covariance calculated from the coupled state ensemble, the ocean state is adjusted by assimilating wind data using the ensemble Kalman filter. As revealed by a series of assimilation experiments using simulated observations, the coupled assimilation of wind observations yields better results than the assimilation of SST observations. Specifically, the coupled assimilation of wind observations can help to improve the accuracy of the surface and subsurface currents because the correlation between the wind and ocean currents is stronger than that between SST and ocean currents in the equatorial Pacific. Thus, the coupled assimilation of wind data can decrease the initial condition errors in the surface/subsurface currents that can significantly contribute to SST forecast errors. The value of the coupled assimilation of wind observations is further demonstrated by comparing the prediction skills of three 12-year (1997–2008) hindcast experiments initialized by the ocean-only assimilation scheme that assimilates SST observations, the coupled assimilation scheme that assimilates wind observations, and a nudging scheme that nudges the observed wind stress data, respectively. The prediction skills of two assimilation schemes are significantly better than those of the nudging scheme. The prediction skills of assimilating wind observations are better than assimilating SST observations. Assimilating wind observations for the 2007/2008 La Niña event triggers better predictions, while assimilating SST observations fails to provide an early warning for that event. 相似文献
16.
Kazuhito Ichii Michael A. White Petr Votava Andrew Michaelis Ramakrishna R. Nemani 《水文研究》2008,22(3):347-355
Snow is important for water management, and an important component of the terrestrial biosphere and climate system. In this study, the snow models included in the Biome‐BGC and Terrestrial Observation and Prediction System (TOPS) terrestrial biosphere models are compared against ground and satellite observations over the Columbia River Basin in the US and Canada and the impacts of differences in snow models on simulated terrestrial ecosystem processes are analysed. First, a point‐based comparison of ground observations against model and satellite estimates of snow dynamics are conducted. Next, model and satellite snow estimates for the entire Columbia River Basin are compared. Then, using two different TOPS simulations, the default TOPS model (TOPS with TOPS snow model) and the TOPS model with the Biome‐BGC snow model, the impacts of snow model selection on runoff and gross primary production (GPP) are investigated. TOPS snow model predictions were consistent with ground and satellite estimates of seasonal and interannual variations in snow cover, snow water equivalent, and snow season length; however, in the Biome‐BGC snow model, the snow pack melted too early, leading to extensive underpredictions of snow season length and snow covered area. These biases led to earlier simulated peak runoff and reductions in summer GPP, underscoring the need for accurate snow models within terrestrial ecosystem models. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
17.
Cheng Y Li X Xu Q Garcia-Pineda O Andersen OB Pichel WG 《Marine pollution bulletin》2011,62(2):350-363
Oil spills are a major contributor to marine pollution. The objective of this work is to simulate the oil spill trajectory of oil released from a pipeline leaking in the Gulf of Mexico with the GNOME (General NOAA Operational Modeling Environment) model. The model was developed by NOAA (National Oceanic and Atmospheric Administration) to investigate the effects of different pollutants and environmental conditions on trajectory results. Also, a Texture-Classifying Neural Network Algorithm (TCNNA) was used to delineate ocean oil slicks from synthetic aperture radar (SAR) observations. During the simulation, ocean currents from NCOM (Navy Coastal Ocean Model) outputs and surface wind data measured by an NDBC (National Data Buoy Center) buoy are used to drive the GNOME model. The results show good agreement between the simulated trajectory of the oil spill and synchronous observations from the European ENVISAT ASAR (Advanced Synthetic Aperture Radar) and the Japanese ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array L-band Synthetic Aperture Radar) images. Based on experience with past marine oil spills, about 63.0% of the oil will float and 18.5% of the oil will evaporate and disperse. In addition, the effects from uncertainty of ocean currents and the diffusion coefficient on the trajectory results are also studied. 相似文献
18.
19.
The seasonal cycle of the main lunar tidal constituent M 2 is studied globally by an analysis of a high-resolution ocean circulation and tide model (STORMTIDE) simulation, of 19 years of satellite altimeter data, and of multiyear tide-gauge records. The barotropic seasonal tidal variability is dominant in coastal and polar regions with relative changes of the tidal amplitude of 5–10 %. A comparison with the observations shows that the ocean circulation and tide model captures the seasonal pattern of the M 2 tide reasonably well. There are two main processes leading to the seasonal variability in the barotropic tide: First, seasonal changes in stratification on the continental shelf affect the vertical profile of eddy viscosity and, in turn, the vertical current profile. Second, the frictional effect between sea-ice and the surface ocean layer leads to seasonally varying tidal transport. We estimate from the model simulation that the M 2 tidal energy dissipation at the sea surface varies seasonally in the Arctic (ocean regions north of 60°N) between 2 and 34 GW, whereas in the Southern Ocean, it varies between 0.5 and 2 GW. The M 2 internal tide is mainly affected by stratification, and the induced modified phase speed of the internal waves leads to amplitude differences in the surface tide signal of 0.005–0.0150 m. The seasonal signals of the M 2 surface tide are large compared to the accuracy demands of satellite altimetry and gravity observations and emphasize the importance to consider seasonal tidal variability in the correction processes of satellite data. 相似文献
20.
Caballero A Espino M Sagarminaga Y Ferrer L Uriarte A González M 《Marine pollution bulletin》2008,56(3):475-482
A main conclusion following the oil spill from the Prestige tanker was that improvements in ocean circulation models were necessary; this was in order to predict, more accurately, the trajectories followed by the oil slicks and hence assist in fight against oil pollution operations. In this contribution, the results of the validation of a semi-empirical ocean circulation model, parameterised for the Bay of Biscay and forced with operational oceano-meteorological remote sensing observations, are shown. The model results have been validated with observations from drifting buoys, deployed in the Bay of Biscay during the crisis. The results show that the model explains a relatively large percentage of the current variability. The comparisons between the real and the estimated drifter trajectories indicate that for 3, 5 and 7 day-long trajectories, the drifter position is estimated with errors of approximately 23, 35 and 46km, respectively. The model reproduces relatively well the trajectory followed by the drifter with the shortest period (23 days). 相似文献