共查询到20条相似文献，搜索用时 343 毫秒
1.
Variability of the water temperature in the western Wadden Sea on tidal to centennial time scales 总被引：1，自引：1，他引：0
Daily observations of the sea surface temperature in the Marsdiep tidal inlet, which connects the shallow Dutch western Wadden Sea with the deeper North Sea, already started in the summer of 1860, over 140 years ago. Since the year 2000 the sampling frequency has strongly increased because of the use of electronic sensors and data logging by computer. Analysis of these temperature data has revealed variations with time scales from tidal, daily, seasonal, inter-annual, to centennial. The tidal temperature variations are generated by advection of the seasonally varying temperature gradient between Wadden Sea and North Sea, while the daily variations are mainly caused by the daily variation of solar radiation. The seasonal variation in sea surface temperature only lags a few days behind the coastal surface air temperature, contrary to the sea surface temperature in the deeper nearby North Sea, which is delayed with about 1 month. The North Atlantic Oscillation index has been used as large-scale proxy for the atmospheric forcing of the Wadden Sea temperature. Only for the winter and spring a significant correlation is found between temperature and the winter index. However, this correlation is so strong that also the annual mean temperature is correlated significantly with the North Atlantic Oscillation. At longer time scales, from decadal to centennial, also large temperature variations are observed, of the order of 1.5 °C. However, these are not related to long-term changes of the North Atlantic oscillation. These long-term temperature changes involve a cooling of about 1.5 °C in the first 30 years of the record and a similar warming in the last 25 years. In between, these long-term changes were smaller and more irregular. Similar conclusions can also be applied to individual seasons as well as to the date of the onset of spring. 相似文献
2.
Due to limit of coverage in TOPEX/Poseidon (T/P) satellite and sparseness of in-situ tide gauges around Antarctica, the accuracy of global ocean tide models in Antarctic seas is relatively poorer than in low- and mid-latitude regions. To better understand ocean tides in Prydz Bay, east Antarctica, a GPS receiver was deployed on floating sea ice to measure tide-induced ice motion in multiple campaigns. Four online Precise Point Positioning (PPP) services are used to process the GPS data in the kinematic PPP mode, and UTide software is used to separate the major tidal constituents. Comparison between results from different processing methods (relative processing solutions from Track, kinematic PPP solutions from online services) and with bottom pressure gauge (BPG) shows that, high-accuracy tidal information can be obtained from GPS observations on floating sea ice, the root-sum-square (RSS) for the eight major constituents (O1, K1, P1, Q1, M2, S2, N2, K2) is below 4 cm. We have also studied the impacts of data span and filter edge effects at daily boundaries on the accuracy of tide estimates, and found that to obtain reliable tide estimates and neglect the filter edge effects, continuous observation longer than 30 days is necessary. Our study suggests that GPS provides an independent method to estimate tides in Prydz Bay, and can be an alternative to tidal gauges, which are costly and hard to maintain in Antarctica. 相似文献
3.
4.
JASON-1与TOPEX/POSEIDON卫星高度计数据在中国海和西北太平洋的一致性分析及印证 总被引：1，自引：0，他引：1
利用JASON-1和TOPEX/POSEIDON卫星高度计在相互校正阶段的观测资料,对两者在中国海和西北太平洋测得的海面风速、有效波高、后向散射截面、海平面高度等参数进行一致性分析;利用j,v模型及主要分潮的调和常数,对中国陆架浅海的JASON-1海平面高度数据进行浅海潮汐修正,使用验潮站月平均水位资料对修正结果加以印证。结果显示,2颗高度计观测的海洋环境参数具有强相关性,JASON-1具备了完成延续TOPEX/POSEIDON数据集这一使命的条件。但是,2套系统对于同一海洋环境参数的观测还是存在不能忽略的差异,对这种差异进行了分析,并给出了修正模型。所使用的浅海潮汐修正方法有效地抑制了中国陆架浅海潮波对海平面高度反演的影响,所使用浅海水域的5个验潮站月平均水位资料与JASON-1高度计经过浅海潮汐修正后的海平面高度的相关系数为0.738,标准偏差为0.096m。通过进一步融合JASON-1和TOPEX/POSEIDON在并行飞行期间的海平面高度数据并与验潮站资料比较显示,两者的相关系数提高到0.83,标准偏差为0.067m。 相似文献
5.
6.
南海潮汐主要分潮振幅变化趋势研究 总被引：1，自引：1，他引：0
潮汐变化研究对于海洋工程、沿海地区洪涝灾害预防、海上交通等各个方面都有着重要的意义。由于验潮站都集中在近海,所以之前潮汐变化研究主要集中在近海海域。相比之下,深海地区由于长期高频水位观测的缺乏导致相关的潮汐变化研究非常少。基于近海验潮站数据和深海卫星高度计数据,本文首次用非平稳潮汐调和分析工具包S_TIDE提取了南海4大主要分潮(M2、S2、K1、O1)振幅的长期趋势。研究发现在南海大部分地区,4大主要分潮的振幅都是比较稳定的,不存在显著的上升趋势或下降趋势。在南海少部分地区4大主要分潮的振幅存在显著的趋势,最大的上升趋势可达2.91 mm/a,最大的下降趋势可达3.50 mm/a。该海域潮汐的长期趋势可能与内潮海表面信号的变化有关。卫星观测到的潮汐既包含正压潮,也包含内潮海表面信号。南海作为全球内潮活动最活跃的海域之一,其内潮海表面信号是非常显著的。而内潮对海洋层化的变化是非常敏感的,海洋层化的变化会影响内潮的生成、传播和耗散以及内潮在海表的显示,最终引起该海域潮汐振幅的长期趋势。 相似文献
7.
Year long measurements of bottom pressure were made at 2,036 m depth in Sagami Trough, at 2,538 m depth in Suruga Trough, and at 32 m depth in the south of Minami-Daitojima Island. Amplitudes and phase lags of the major constituents of tides were estimated by the response method, and they were compared with the observational results at several tide stations operated by the Japan Meteorological Agency. A comparison with Schwiderski's global models for the eight tidal constituents showed that the amplitudes were in good accordance to one another within 3 cm, and that the differences of phase lags were less than 15°. The largest portion of the variations of the bottom pressure was caused by the tides: the variance of the major eight constituents was more than 98.5% as large as the total variance. The measurements show that tidal waves can be recorded offshore with a sufficient accuracy by the quartz sensors. Drifts of indication of the pressure gauges were significant and they prevented detection of a long-term variation which might be caused by fluctuations of the ocean currents or by the eddies. 相似文献
8.
K.O.L.F. Jayaweera 《Ocean Engineering》1976,3(5):293-294
Infrared (i.r.) imagery from the NOAA 2,3, and 4 satellites could be used to measure accurately the absolute temperature of the sea surface and sea water. Comparison with measured temperatures indicate that the satellite observed values are within 2°C of those measured. Contouring temperatures and observing temperature fluctuations within 0·5°C is also possible by enhancing the infrared image. This is done by confining the 16 steps of gray of the image to a desired small temperature scale. The existence of open water areas within the pack ice and the positions of the ice edges could be readily distinguishable by generating special imagery in such a way that the gray scale covers two temperature ranges with a gray tone jump at the freezing point of sea water. In this way ice-water boundary appears as a line of demarcation between two different gray tones. Because the i.r. imagery is available all year round these techniques are readily applicable at all times especially during the winter months when the low sun angles make visible imagery not useful. 相似文献
9.
10.
The scarcity of tide gauges in a global scale and the variability of the tidal levels along contiguous coasts mainly due to changing hydrographic conditions make the determination of tidal levels, especially of the Mean Sea Level, not an easy task. Determination of such levels with a precision of about 10 cm, necessary for most coastal engineering works, is usually based on records of temporary tide gauges or on geomorphological techniques. In this paper we present an alternative approach permitting to accurately identify tidal levels with a precision suitable for civil engineering applications based on biological observations on rocky shores, including breakwaters and quays. More specifically, we present evidence that the biological zonation, i.e. the distribution of coastal species in well-defined sub-horizontal belts, is practically insensitive to seasonal and other small-scale fluctuations of the sea level and is clearly related to certain levels, mostly the Mean Low Water (MLW). This approach, somewhat similar to what has been used in the past (for instance for the determination of the geodetic vertical datum in the Republic of Venice, Italy, till approximately AD 1800), permits direct determination of the Mean Sea Level or of other tidal levels on the basis of biological observations without statistical analyses of tide-gauge records with an accuracy of 5–10 cm, especially in microtidal, low-energy coasts. 相似文献
11.
In this paper , we present a novel Kalman filter approach to combine a hydrodynamic model-derived lowest astronomical tide (LAT) surface with tide gauge record-derived LAT values. In the approach, tidal water levels are assimilated into the model. As such, the combination is guided by the model physics. When validating the obtained “Kalman-filtered LAT realization” at all tide gauges, we obtained an overall root-mean-square (RMS) difference of 15.1 cm. At the tide gauges not used in the data assimilation, the RMS is 17.9 cm. We found that the assimilation reduces the overall RMS difference by ～ 31% and ～ 22%, respectively. In the Dutch North Sea and Wadden Sea, the RMS differences are 6.6 and 14.8 cm (all tide gauges), respectively. Furthermore, we address the problem of LAT realization in intertidal waters where LAT is not defined. We propose to replace LAT by pseudo-LAT, which we suggest to realize similarly as LAT except that all water level boundary conditions and assimilated tidal water levels have to be enlarged by a constant value that is removed afterward. Using this approach, we obtained a smooth reference surface for the Dutch Wadden Sea that fits LAT at the North Sea boundary within a few centimeters. 相似文献
12.
TOPEX/POSEIDON高度计浅海潮汐混淆的初步分析 总被引：22，自引：5，他引：17
根据对卫星轨道特征和观测结果的分析,对TOPEX/POSEIDON(简称T/P)星载高度计在我国近海的潮致混淆现象进行了初步研究.分析表明,在浅海区T/P高度计的观测结果存在很强的潮致高频混淆.NASA分发的地球物理记录中所提供的潮汐订正值虽适用于大洋,但不能有效地除去浅海潮汐.虽然如此,T/P潮致混淆的主要频段的周期小于90d,因而可以通过滤波方法提取周期较长的海面高度季节信号,从而用于季节环流(如南海季风环流)的研究.采用FFT/IFFT方法滤波试验的结果显示,T/P的海面高度观测结果有很高的精度,滤波处理后的海面高度距平变化和地面潮位观测结果一致性良好,上、下行轨道交叉处相邻测点间的标准偏差在3cm左右,可满足南海环流研究的需要. 相似文献
13.
压力验潮仪在将压力换算成潮位时,重力、温度和盐度的误差会引入到潮位数据中,根据中国沿岸重力、温度和盐度的分布情况,对这一误差进行分析探讨。 相似文献
14.
Vilibic I. Dadic V. Ivankovic D. Beg Paklar G. Cupic S. 《Oceanic Engineering, IEEE Journal of》2007,32(2):428-435
This paper encompasses the analyses of sea level data measured at four tide gauges situated in the city of Split, Croatia. Two old long-term stations comprise float-type instruments in stilling wells, with analog recording on a chart, while two modern stations were installed in 1999 and 2000, calculating sea level height from the measured sea and air pressure. Although analog recording devices with a drum may suffer from inaccuracy in timing and drum rotation speed, clock errors, and vertical pencil position, the largest errors in the data came from the digitizing process, which is subjected to the individual work of a technician. Although, the data collected with pressure systems are supposed to be more homogeneous and accurate, after several years of work, the sensors usually have a drift in time. This problem turned out to be accompanied with lower quality sensors being part of wider automatic measuring systems, whereas the station which has been specially designed for sea level measurements showed no drifts in four years of operating. Therefore, one should be careful in choosing measuring equipment between various manufacturers. In addition, the equipment should be regularly checked since the malfunction in global positioning system (GPS) clock resulted in time drift of sea level data of more than an hour. 相似文献
15.
A non-destructive temperature calibration system for expendable bathythermographs (XBT) is described. A transfer standard technique has been used to estimate XBT thermistor probe-to-probe temperature variability. One-point calibration results suggest that a standard deviation of 0.025°C is typical at 10°C. Additional calibration data from nine XBT thermistors suggest that probe-to-probe temperature variability is largest at 0°C (ca. 0.03°C) and decreases uniformly to a minimum at 30°C (ca. 0.01°C). 相似文献
16.
The BIO Mark 8 thrust anemometer measures the drag of the wind on a perforated table tennis ball mounted on a vertical beam. The tri-axial displacement of the beam is sensed by eddy current proximity sensors. This anemometer has a flat frequency response from 0 to 10 Hz and can measure wind from 0 to 28 m s−1 at temperature from − 19 to + 28°C. It is designed for remote operation for extended periods of time such as on stable towers at sea. 相似文献
17.
本文基于船载及锚定ADCP、CTD观测,获得了大、小潮时的温度、盐度、浊度、潮位、流速等观测数据,研究杭州湾南部的一个主要弯曲航道——螺头水道内的潮流动力学特性。螺头水道水深超过100 m、最大潮差大于2.5 m。涨潮时,强潮流速出现在水道北岸,落潮时,强潮流速出现在水道南岸,最大流速值分别为约2 m/s和1.8 m/s。受压强梯度、密度梯度、科氏力和离心力影响,涨落潮过渡时在水道的横断面产生较为明显的环流。夏季存在较弱的层化现象,深水处受环流的影响,盐度、温度的混合较强。锚定观测数据表明,温度、盐度的变化频率与潮流的变化频率相似,但存在高于M2分潮频率的谱峰值。因此,笔者认为潮流与横向环流的相互作用,可能导致更高频率的盐度和温度变化。 相似文献
18.
The purpose of this study is to investigate the influence of tidal currents on sea ice in Spitsbergen fjords which may cause rapid decrease of the ice thickness due to erosion and melting of the ice. The effect was studied in-situ near the narrow channel connecting the Van Mijen Fjord and Lake Vallunden. The strong jet-like tidal currents in the strait driven by semidiurnal tide continue into the lake preventing ice freezing along a narrow strip during high tide and relatively warm weather. Understanding the formation of open water regions or regions with thin ice is important for the safe transportation on ice. We estimate conditions and representative time over which strong tidal current influences ice thickness along a narrow strip in solid ice. Changes of tidal phase and decrease in air temperature influence freezing of the strip in one-two days. While the tidal flow leaves the strait it overflows a shallow bar and generates internal lee waves propagating downslope and mixing the water. Tidal forcing of internal waves was measured using pressure gauges and by scanning of the ice surface during flood and ebb phases. Internal waves were measured using three types of CTD instruments and an ADCP current meter. The generation of wave packets occurs every tidal cycle when the current flows into the lake, but no generation occurs during the ebb phase of the tide because the currents over the bar slope are low. Parameters of internal waves are estimated. Model simulations confirm generation of internal wave train by the tidal current descending downslope. 相似文献
19.
20.
G. Reverdin P. Delcluse C. Lvy P. Andrich A. Morlire J.M. Verstraete 《Progress in Oceanography》1991,27(3-4)
Isotherm vertical displacements within the thermocline and surface currents were investigated in the tropical Atlantic Ocean from 12°N to 12°S in 1982–1984, the period of the FOCAL-SEQUAL experiment. The study is based on a numerical simulation of an oceanic general circulation model tuned for the study of the equatorial regions, and on the analysis of the large scale thermocline displacements and currents using observed temperature profiles. Ground truth is provided by temperature and currents from moorings, records from inverted echo sounders and tide gauges as well as from drifting buoys. Comparison of the analysis with the ground truth shows that some important aspects of the low frequency variability are “captured” by the analysis when the data base is large enough.On large scales, the simulation generally resembles the analysis. Along the equator, the upwelling signal propagates eastward. The seasonal set-up of the westerly winds is associated with large westward currents, and a following overshoot of the zonal dynamic topography. Otherwise, the zonal dynamic topography is in near-equilibrium with the winds. The North Equatorial Countercurrent is portrayed comparably in the analysis and the simulation, where, after starting as a narrow eastward flow near 5°N, it extends northward through the northern summer. Interannual variations are found both in the analysis and the simulation. In particular, the thermocline flattened early in 1984.However, the simulation differs in significant respects from the real world: the equatorial undercurrent is too weak in the east and the model produces too much variability south of the equator. The 20°C isotherm is too shallow above the core of the thermocline, and the surface layer is too stratified. Because the surface layer is where the wind stress, main forcing of the model is applied, major effort will have to be devoted to parameterizing the near-surface downward mixing of momentum, heat and fresh water. 相似文献