共查询到20条相似文献，搜索用时 84 毫秒
1.
根据1975—2017年冬、夏季节渤、黄海沿岸25个气象站风观测资料,采用二维非线性垂直平均风生流模式、旋转经验正交函数(REOF)等方法,研究了渤、黄海冬、夏季节平均风生流速度势与流函数场年际变化时空模态与环流变异.由于冬、夏季节渤、黄海风应力场强度年际变化显著线性减弱趋势,冬季渤、黄海平均速度势与流函数强度年际变化线性减弱速率大于夏季,黄海冬、夏季平均速度势与流函数强度年际变化线性减弱速率大于渤海.渤、黄海冬、夏季节平均风生流速度势与流函数场年际变化主要有两种时空模态,冬季渤海垂直环流显著线性减弱以及水平环流准平衡态年际变化是主要分量,冬季黄海垂直与水平环流准平衡态年际变化是主要分量.夏季渤海垂直环流显著线性减弱以及水平环流准平衡态年际变化是主要分量,夏季黄海大部分海域垂直环流显著线性减弱与局部垂直环流显著线性增强年际变化是主要分量,夏季黄海水平环流形态此消彼长显著线性增强及减弱年际变化是主要分量.冬季黄海暖流暖水向南黄海西侧以及向渤海中部输送过程是在3～4个环流之间传递形成,并非由单一环流输送形成.冬季渤海中部辐散下沉反气旋环流与黄海中部至渤海海峡的气旋环流、黄海东部辐散下沉反气旋环流是冬季黄海暖流强度与范围的控制环流,夏季渤海中部辐散下沉反气旋环流与黄海中部辐合上升气旋型环流是夏季渤、黄海冷水团强度与范围的控制环流,冬、夏季节渤、黄海控制环流年际变化形态的变换形成冬季黄海暖流与夏季渤、黄海冷水团暖年或冷年的年际变化. 相似文献
2.
根据1978—2015年渤、黄海沿岸观测风应力场与二维非线性垂直平均风生流模式，以及旋转经验正交函数（REOF）、调和分析等方法，研究了渤、黄海月平均风生流速度势、流函数场季节循环时空模态与年际变异.渤、黄海月平均风生流速度势、流函数场主要有两种时空模态，季节周期分量是时空模态的主要分量.由于风应力场季节循环变异，渤海流函数场季节时空循环变异程度大于速度势场，速度势、流函数场第二模态是季节变异的主要分量，黄海速度势场季节时空循环变异程度大于流函数场，速度势场第二模态是季节变异的主要分量.由于月平均风应力场强度年际变化显著线性减弱，渤、黄海季节平均风生流场强度年际变化也显著减弱.渤、黄海暖流与冷水团季节生消是风生流水平环流与垂直对流对冷 暖水体输送与汇集共同作用的结果，渤、黄海春、夏季辐合上升环流延缓及减弱了浅层暖水向深层传播，是春、夏季冷水团与温跃层形成的重要动力因素，因此，速度势是研究渤、黄海风生流场十分重要的因素.冬季渤海中部、黄海东部反气旋型及辐散下沉环流与黄海中部气旋型环流、辐合上升环流是黄海暖流季节转换与强度的主要动力控制因素，夏季黄海东部气旋型环流、辐合上升环流与黄海中部反气旋型环流、辐散下沉环流是黄海冷水团季节转换与强度的主要动力控制因素. 相似文献
3.
提出地磁日变改正中需要顾及地磁长期变化和磁扰的可靠分离,保证磁力数据改正处理具有明确的基准,提高拼接整合的精度.如果日变站能够控制测区,两者可采用时间同步固定的地磁正常场作为磁异常基准,测区的地磁长期变化由日变站实测的地磁长期变化来改正,反之,对日变站和测区应分别采用时间同步变化的地磁正常场作为磁异常基准,测区的地磁长期变化由地磁正常场的地磁长期变化来改正.为此,应该明确定义与时间相关的日变改正基值为地磁正常场与地磁异常之和.通过磁静日总场观测值偏离正常场的某种形式的长期平均值,可以逼近日变站的地磁异常.磁扰的分离应保证磁扰初动和消失相对于磁静日无磁扰的连续过渡.采用综合模型一并进行日变改正、正常场及其长期变化改正,可以更好地解决目前日变改正中遇到的问题. 相似文献
4.
Climate teleconnections at monthly time scales in the Ligurian Sea inferred from satellite data 总被引：1，自引：0，他引：1
The existence and spatial distribution of possible teleconnections between the South Pacific and North Atlantic oceans and the Ligurian Sea (North-western Mediterranean) are investigated in the present paper. Teleconnections are searched by cross-correlating monthly spatio-temporal time series of 1.1 km resolution sea surface temperature (SST), and a 22.2 km resolution sea level anomaly (SLA), measured from satellite from March 1993 to August 1999, with two indices characterising the South Pacific and the North Atlantic variability: the Southern Oscillation (SO) and the North Atlantic Oscillation (NAO) indices, respectively. Concerning the variability induced by the North Atlantic Ocean, it is shown that it mostly influences the SLA field in the Ligurian Sea. Specifically, relevant anti-correlations between SLA and North Atlantic variability have been found in all the Ligurian sub-basin. As expected by geographical proximity, the effects of North Atlantic on the SLA field in the Ligurian Sea are instantaneous at monthly time scales. Instead, correlations between SST and NAO Index are found at time lag τ = 1 month in the southern part of the basin highlighting the memory of the ocean related to their heat capacity. Significant anti-correlations between SO Index and the SST field in the Ligurian Sea, were obtained at time lag τ = 4 months in the coastal areas of the sub-basin. Results also indicate that the impact of teleconnections in the area studied is not geographically uniform. 相似文献
5.
减弱船磁效应对海洋地磁测量精度影响的方法研究 总被引：1，自引：0，他引：1
船磁效应一直是影响海洋地磁测量精度的一个重要因素。传统船磁模型只取磁方位角为变量,改正后测线数据存在系统差和船磁影响的起伏变化,给不断累积的地磁数据拼接带来困难。磁正西北和北东方向的测线网受船的感应磁性变化的影响最小,东西向测线之间船磁影响差异最小,而磁南北向测线之间正好相反,据此可从测线布设方案着手减弱船磁效应影响。完备的船磁模型可以兼顾考虑测线航向、地磁总场、磁倾角和拖缆长度的变化,通过不同拖缆长度的主、副测线网交点差平差或三点各两种不同拖缆长度的方位测量,实现地磁异常分离和完备船磁效应的改正。实例说明固定船磁,甚至负的垂直分量,会使船磁效应随纬度出现可观变化,需要完备船磁模型的解算和改正才能解决这个问题。 相似文献
6.
Using all available geomagnetic data, including those obtained in a detailed survey conducted by the authors in 1970, the geomagnetic anomaly pattern if the Japan Sea has been studied. It has been established that sublinear magnetic anomalies run subparallel to the general trend of the Japanese Islands. The peak to peak amplitudes of most of these anomalies are less than 300y, their wavelengths 20 to 40 km. The anomalies are much less distinct in linearity than those found in the northwestern corner of the Pacific basin off northeastern Honshu. The linear trend is better developed in the deeper basin areas and less recognizable in the Yamato- and Kitayamato-areas. The anomaly pattern appears to support the view that the Japan Sea floor evolved through a spreading process from numerous spreading centers. A definite conclusion about the genesis of the Japan Sea, however, must await further investigation. 相似文献
7.
局部海洋地磁场模型可以为水下地磁匹配导航与磁性目标探测等工作提供高精度的海域地磁背景场数据。针对目前区域地磁场模型构建方法中未考虑到高度或深度变化的影响,截断阶数难以确定及存在边界效应等问题。根据海洋磁力测量的特点,顾及磁测点高度数据,引入粒子群优化的最小二乘支持向量机法(PSO-LSSVM)构建局部海洋三维地磁场模型。在仿真与实测数据建模试验中,与Taylor多项式法、BP神经网络法及曲面样条函数法比较,结果表明,无论是在地磁变化平缓区还是复杂区,PSO-LSSVM法的建模精度均是最高的,建议在局部海洋地磁场模型构建中采用。 相似文献
8.
9.
研究分析了最新的国际地磁参考场模型IGRF-13的数据来源及模型特征,并与以往模型进行了精度对比。在此基础上,结合不同时期获取的海洋磁力数据融合的实际需求,制定了海洋磁力正常场校正方法及磁力异常重计算流程。选取了南海试验区和太平洋试验区的调查数据,应用最新国际地磁参考场IGRF-13对其进行了正常场校正和磁力异常重计算,得出以下结论：（1）磁力正常场模型IGRF-13包含1900-2025年的26个磁力模型,可采用该模型对以往不同时期获取的磁力数据进行统一重计算;（2）应用最新IGRF-13对南海、太平洋试验区的磁力异常数据进行重计算后,数据内符合精度提升了0.05～0.20 nT;(3)建议在对不同年代的地磁数据融合应用前,先消除时变效应。本文提出的地磁正常场校正方法适用于减弱长期变化磁场的时变效应影响,提升磁力成果数据精度。 相似文献
10.
11.
南海中尺度涡温盐结构的季节特征及形成机制 总被引：2，自引：0，他引：2
本文利用最新的涡旋数据集和ARMOR3D数据，研究了南海中尺度涡温盐结构的季节特征及形成机制。合成分析的结果表明，在冬季，涡旋引起温度异常的水平分布在50米以浅表现为类似偶极型分布，而在50m以深则趋向于中心对称分布；在夏季，温度异常的水平分布均表现为中心对称的特征。涡旋引起盐度异常的水平分布也具有类似的季节特征，但是偶极型中的不对称性相对较弱。在垂向上，涡旋所致的温度异常表现为单层结构，而盐度异常则为三层结构。进一步的分析表明，涡旋所致温盐异常的垂向分布特征与背景温盐的垂向分层有关；而在50m以浅，温盐异常的水平分布的不对称特征主要由背景温盐场的水平平流所致。 相似文献
12.
Kohei Mizobata Koji Shimada Rebecca Woodgate Sei-Ichi Saitoh Jia Wang 《Journal of Oceanography》2010,66(3):405-424
We estimated the northward heat flux through the eastern channel of the Bering Strait during the ice-free seasons between
1999 and 2008. This is likely about half of the total heat flux through the strait. The net volume transport and heat flux
through the eastern channel of the strait were estimated from multiple linear regression models with in-situ/satellite remotely sensed datasets and NCEP reanalysis 10 m wind. The net volume transport was well explained by the west-east
slope of sea level anomaly and NNW wind component at the strait. On the heat flux, the contributions of both barotropic and
baroclinic components were taken into account. Estimated volume transport and vertical profile of temperature were used to
calculate northward heat flux through the eastern channel of the strait. The magnitude of the estimated heat flux is comparable
to estimates from in-situ measurements. Averaged heat flux in the eastern Bering Strait between 2004 and 2007 was about 1.9 times larger than that
between 2000 and 2003. Maximum heat flux occurred in 2004, and same magnitude of heat flux was estimated from 2005 to 2007.
This resulted not only from the increase in northward volume transport but also anomalous warm water intrusion from the Bering
Sea. Our results suggest a candidate among the important parameters controlling heat budget, which contributes to the Arctic
sea ice reduction, whereas more studies are required to confirm that this mechanism is actually responsible for the interannual
and longer timescale variability. 相似文献
13.
A marine magnetic survey was conducted over the Dellwood Knolls area of the northeast Pacific in September 1977 using a proton precession magnetometer and Loran-C positioning. Geomagnetic field reference stations were located at Victoria and Port Hardy. In addition, a recently developed ocean bottom magnetometer was deployed in the survey area. The cross-over error, a measure of survey accuracy, and the factors contributing to it are discussed. In high magnetic gradient regions, the part of the error related to the uncertainty in ship position implies that the repeatability of the Loran-C navigation system is of the order of 30 metres. Part of the error is also due to time variations of the geomagnetic field. This latter effect can be significantly reduced by correcting to a well located reference station. Because of the areal distribution of the geomagnetic coast effect, a land station close to the survey area may not be as effective as a more distant site. Referencing to an ocean bottom magnetometer, at least to moderate levels of disturbance, is comparable to correcting to a well located land station. Using a combination of land and ocean bottom reference data produced a reduction in the cross-over error from 25 to 11 nT for this survey, effectively removing the geomagnetic variation term. This technique should prove even more useful for surveys conducted during periods of higher geomagnetic activity.Contribution from the Earth Physics Branch No. 824. 相似文献
14.
This paper shows the results of a detailed reprocessing of aeromagnetic data, obtained by the downward projection to the seabed. The area of interest is centered over the Tyrrhenian Basin, whose bathymetric–topographic lay-out is characterized by a somewhat irregular trend. The origin of the intense depth variations depends on the Tyrrhenian structural setting, that is associated with the presence of several tectonic lineaments, seamounts or volcanic islands. The data were characterized by good quality and dense sampling, but they have been reprocessed in order either to solve some problems in the original compilation, and to reduce the distortion of the geomagnetic anomaly field caused by the difference of distance between the survey level and the magnetic source. The reprocessed magnetic map is proposed as an effective analysis tool for the Tyrrhenian area that is characterized by high susceptibility lithotypes. Downward projection of the aeromagnetic data by BTM algorithm increases the definition of the anomalous magnetic signal without distortions in the geometric pattern of the field, thus showing a more stable and effective association between the magnetic anomalies and their geological sources. This effect is particularly true for high frequency anomalies that are directly comparable after the topographic projection because the depth filtering effect is attenuated. Moreover, the BTM method has been applied for the first time to a regional scale survey that shows substantial advantages because no fictitious anomalies in the high frequency sector of the spectrum were generated. This has been a typical effect of the traditional downward projection methods widely used before. The final result is a BTM anomaly map that is able to show the structural connections between the geological magnetic sources of the Tyrrhenian Sea area. 相似文献
15.
本文作者所在单位1988年在舟东共测得地磁剖面67条,剖面总长度为2978km。根据测网中306个测线交点上交点差的方均根值,确定精度为3nT,这次测量是东海陆架区油气勘探调查的一部分。 相似文献
16.
17.
Idealized numerical experiments with a depth level coordinate ocean circulation model (GFDL MOM3) have been conducted to investigate
the structure of interdecadal variability from thermally driven circulations. The model oceans are driven by steady surface
heat fluxes in the absence of surface wind stresses. Interdecadal variability is observed, with characteristics similar to
those reported in many previous studies. To explain the nature of the variability we propose a new mechanism based on two
local horizontal advective processes. This overcomes the limitations in previous theories based on the interplay between global
properties such as zonal and meridional temperature gradients and overturning. One of the two advective processes is a zonal
flow anomaly induced by a temperature anomaly along the northern wall through geostrophy southward of the temperature anomaly.
A cold (warm) anomaly along the northern wall produces a positive (negative) zonal flow anomaly that induces a warm (cold)
temperature anomaly by enhancing (weakening) warm advection from the western boundary along the path of the zonal flow anomaly.
The temperature and flow anomalies are transported toward the eastern boundary by the mean eastward zonal flow. When the positive
(negative) zonal flow anomaly that accompanies the warm (cold) temperature anomaly encounters the eastern wall, a downwelling
(upwelling) anomaly is produced. To dissipate the vorticity due to this downwelling (upwelling) anomaly, a northward (southward)
flow anomaly, which is another advective process governing the variability, is generated within a frictional boundary layer
next to the eastern wall. The northward (southward) flow anomaly circulates cyclonically along the perimeter of the basin
while enhancing (reducing) warm advection. So does the warm (cold) temperature anomaly carried to the eastern wall by the
mean zonal flow while pushing the cold (warm) anomaly that produced the positive (negative) zonal flow anomaly westward and
initiating the other half cycle of the variability. During the anomalous downwelling or upwelling, the available potential
energy stored in the anomalous density field is released to maintain the variability. Thus, neither barotropic nor baroclinic
instability supplies energy for the variability. The anomalous vertical velocity is stronger along the northern boundary and
the northern part of the eastern boundary. A shallow continental slope added along those boundaries prohibits the anomalous
vertical motion and weakens variability very effectively, while one along the western boundary does not. 相似文献
18.
为了预测南黄海盆地油气远景,利用卫星遥感对东海陆架盆地进行海面温度测量。东海陆架盆地已知油气远景区与卫星热红外温度异常区具有原地重复性,与水气界面CH4含量曲线及海底化探异常吻合程度很好。南黄海盆地卫星遥感海面温度异常区沿南北向 (123o30′) 呈带状分布,与航磁解释出的南北向分布的东部鼻状隆起吻合较好。由于温度异常区主要分布在南黄海盆地东部鼻状隆起的南北端,故推测东部鼻状隆起的南北端具有较好油气远景。 相似文献
19.
Gleb Panteleev Motoyoshi Ikeda Alex Grotov Dmitri Nechaev Max Yaremchuk 《Journal of Oceanography》2004,60(3):613-623
Standard hydrological section data, collected in the eastern Barents Sea in September 1997, have been analyzed using a variational
data assimilation technique. This method allows us to obtain temperature, salinity and velocity fields that are consistent
with observations and dynamically balanced within the framework of a steady-state model describing large-scale nearly geostrophic
circulation. Error bars of the optimized fields are computed by explicit inversion of the Hessian matrix. The optimized velocity
field is in agreement with independent velocity observations derived from surface drifter trajectories in the southwestern
part of the Barents Sea. Optimized fields provide the following estimates of integral characteristics of the circulation in
the region: i) the North Cape current transport is 2.12 ± 0.25 Sv; ii) the Karskie Vorota Strait throughflow is 0.7 ± 0.06
Sv; iii) heat flux with Atlantic water is 4.7 ± 0.16⋅1011 W; iv) salt import from the Atlantic Ocean is 7.41 ± 0.46⋅103 kg/s. The imbalance of the heat budget in the eastern part of the Barents Sea indicates the presence of statistically insignificant
surface heat fluxes which are less than 1 W/m2.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献