基于PAADCP 的海流流速的误差分析及校正方法

为了更加合理、有效地利用海流测速数据,必须进行误差分解和校正。通过分析相控阵声学多普勒海流剖面仪(PAADCP)测试海流流速的原理,提出了海试数据粗差区别与动态校正的算法,采用小波多尺度分析方法,降低了系统误差和随机误差,建立了海流流速的误差分析与校正方法。利用海试实测的垂向流速数据,分析了一般情况下的海流流速的误差,得到垂向流速的均值±0.02 m/s,误差精确度小于0.23 m/s,验证了方法的有效性及合理性。所得算法和方法对于海流测速数据的实时处理和后处理具有实用价值。     

1870-2011年全球海域SST变化趋势

利用来自英国气象局哈德莱中心(Met Office Hadley Centre)的海表面温度(Sea Surface Temperature, SST)资料, 对全球海域近140余年来SST的长期变化进行分析。研究发现:(1)1870—2011年期间, 全球大部分海域的SST表现出显著的逐年线性递增趋势, 在两极大部分海域、格陵兰南部海域呈显著的递减趋势, 仅在部分小范围海域及一些零星海域的SST无显著变化。近海的递增趋势强于大洋, 大洋西岸的递增趋势强于大洋东岸。(2)近140余年来, 整体上全球的SST以0.0038℃/a的速度显著增加, 其中1870—1910年表现出较为显著的递减趋势, 1910年至今表现出较强的递增趋势。(3)1870—1910年期间, 全球大范围海域的SST无显著变化; 呈显著递减的海域主要分布于东海、阿拉斯加半岛南部海域、北大西洋30°N附近海域、冰岛南部海域、南印度洋西风带海域、新西兰附近海域; 呈显著递增的区域较为分散。1910—2011年期间, 全球大范围海域的SST逐年显著递增, 在两极大部分海域呈显著的递减趋势。(4)1870—1960年期间, 两极的SST走势较为平缓; 1960—2011年期间, 南极尤其是威德尔海的SST表现出显著的递减趋势, 其中逐8月的递减趋势尤为强劲; 北极逐2月、逐5月的SST呈显著性递减, 逐8月呈显著性递增且趋势较为强劲, 达到0.0402℃/a, 逐11月的SST无显著变化。     

Detection of ocean waves using satellite altimetry: Application to equatorial Kelvin waves

A new method for wave motion detection from satellite altimetric measurements of sea surface height is presented. The essence of the approach is to construct a two‐dimensional traveling‐wave Fourier series representation of the amplitude field within a prespecified oceanic region. The method employs an iterative, nonlinear least‐squares technique based on the Marquardt‐Levenberg algorithm to solve for model parameters describing characteristic features of the evolving wave system. The Marquardt‐Levenberg Fourier series (MLFS) algorithm was applied to Kelvin waves active during the 1986–1987 El Nino event in the equatorial Pacific ocean using GEOSAT Exact Repeat Mission altimetry data. Characteristics of the wave system were found to be in essential agreement with earlier field measurements and the observations of Cheney and Miller (1987) obtained using time series developed from GEOSAT data. The advantage of the present detection scheme lies in its speed and ability to determine a wave system's dispersion relation over a finite range of wavenumbers, and hence the group velocity of that system.     

Comparison of Grid Averaged Altimeter and Buoy Significant Wave Heights in the Northern Indian Ocean

A quantitative comparison of the collocated inter-annual significant wave height (SWH) data collected between 2006 and 2009 from buoys and altimeters at nine buoy locations (total n = 2241) in the Northern Indian Ocean is attempted for assessing the validity of daily averaged gridded altimeter significant wave height (ASWH) provided by AVISO for operational use. ASWH is underestimated by 0.20 m, the root-mean-square error (RMSE) is less than 0.30 m, the Scatter Index is less than 20%, and the correlation coefficient is greater than 0.90. Further, at three locations, the examination of the above statistics showed that the bias and RMSE is high during the southwest monsoon season compared with the Northeast monsoon. Scatter Index showed only slight variation (14–18%) for different ranges of SWH. The response of the daily average gridded ASWH data during extreme conditions (cyclones) in the vicinity of the buoy locations is poor at all compared buoy locations. The gridded ASWH from different satellite missions provided by AVISO can be used for basin scale validation experiments of the wave model and for climatological studies in the Indian Ocean, except during cyclone conditions.     

Large eddy simulation of turbulence in ocean surface boundary layer at Zhangzi Island offshore

This study uses a large eddy simulation （LES） model to investigate the turbulence processes in the ocean surface boundary layer at Zhangzi Island offshore. Field measurements at Zhangzi Island （39°N, 122°E） during July 2009 are used to drive the LES model. The LES results capture a clear diurnal cycle in the oceanic turbulence boundary layer. The process of the heat penetration and heat distribution characteristics are analyzed through the heat flux results from the LES and their differences between two diurnal cycles are discussed as well. Energy balance and other dynamics are investigated which show that the tide-induced shear production is the main source of the turbulence energy that balanced dissipation. Momentum flux near the surface shows better agreement with atmospheric data computed by the eddy correlation method than those computed by bulk formula.     

Reviewing evidence of marine ecosystem change off South Africa

Recent changes have been observed in South African marine ecosystems. The main pressures on these ecosystems are fishing, climate change, pollution, ocean acidification and mining. The best long-term datasets are for trends in fishing pressures but there are many gaps, especially for non-commercial species. Fishing pressures have varied over time, depending on the species being caught. Little information exists for trends in other anthropogenic pressures. Field observations of environmental variables are limited in time and space. Remotely sensed satellite data have improved spatial and temporal coverage but the time-series are still too short to distinguish long-term trends from interannual and decadal variability. There are indications of recent cooling on the West and South coasts and warming on the East Coast over a period of 20–30 years. Oxygen concentrations on the West Coast have decreased over this period. Observed changes in offshore marine communities include southward and eastward changes in species distributions, changes in abundance of species, and probable alterations in foodweb dynamics. Causes of observed changes are difficult to attribute. Full understanding of marine ecosystem change requires ongoing and effective data collection, management and archiving, and coordination in carrying out ecosystem research.     

Mesoscale features and phytoplankton biomass at the GoodHope line in the Southern Ocean during austral summer

Two sets of high-resolution subsurface hydrographic and underway surface chlorophyll a (Chl a) measurements are used, in conjunction with satellite remotely sensed data, to investigate the upper layer oceanography (mesoscale features and mixed layer depth variability) and phytoplankton biomass at the GoodHope line south of Africa, during the 2010–2011 austral summer. The link between physical parameters of the upper ocean, specifically frontal activity, to the spatially varying in situ and satellite measurements of Chl a concentrations is investigated. The observations provide evidence to show that the fronts act to both enhance phytoplankton biomass as well as to delimit regions of similar chlorophyll concentrations, although the front–chlorophyll relationships become obscure towards the end of the growing season due to bloom advection and ‘patchy’ Chl a behaviour. Satellite ocean colour measurements are compared to in situ chlorophyll measurements to assess the disparity between the two sampling techniques. The scientific value of the time-series of oceanographic observations collected at the GoodHope line between 2004 to present is being realised. Continued efforts in this programme are essential to better understand both the physical and biogeochemical dynamics of the upper ocean in the Atlantic sector of the Southern Ocean.     

Sedimentary facies of Carboniferous–Permian mid-oceanic carbonates in the Changning–Menglian Belt, West Yunnan, Southwest China: Origin and depositional process

Huge carbonate rock bodies ranging in age from the Visean (Middle Mississippian/Early Carboniferous) to the Changhsingian (Lopingian/Late Permian) overlie a basaltic basement in the Changning–Menglian Belt, West Yunnan, Southwest China. These carbonates lack intercalations of terrigenous siliciclastic material throughout. These lines of evidence indicate that they formed upon an isolated and continuously subsiding mid-oceanic island (or plateau), probably of hotspot origin. The carbonates are grouped into a shallow-water carbonate platform facies regime observed in the Yutangzhai section and a relatively deep-water carbonate slope facies regime typically represented in the Longdong section. These two facies regimes developed contemporaneously as parts of a carbonate depositional system on and around a mid-oceanic volcanic edifice. The carbonate platform is subdivided into four facies, including platform-margin, shoal, lagoon, and peritidal facies. Along the measured Yutangzhai section of the platform facies regime, the vertical facies succession from the platform-margin facies into inner-platform facies such as the shoal and lagoon facies is recognized. This facies succession is explained as resulting from the progradation of the carbonate platform. Worm tubes occur as a main reef builder in platform-margin facies of the Mississippian. Their occurrence as major constituents in a high-wave-energy reef is peculiar to Carboniferous reef distributions of the world. The occurrences of other reef- and/or mound-building organisms and peritidal dolo-mudstone are almost consistent in timing with those of Panthalassan counterparts such as the Akiyoshi and Omi limestones of Japan, and probably exhibit the worldwide trend.     

基于海洋潮汐动力模型的水位改正方法研究

本文研究并提出了一种基于海洋潮汐动力模型的水位改正方法。该方法通过对数值模拟的天文潮位进行改正,结合残差改正获得特定站的潮位数据。结合实际资料,将基于海洋潮汐动力模型的水位改正方法与传统的水位改正方法(时差法和最小二乘潮位拟合法)进行了比较,新方法改正的精度明显高于传统方法,显示其在地形变化较为复杂海域进行水位改正的可行性与独特优势。该方法可以在海洋测绘中减少短期验潮站的布设,用于潮位序列缺失的修补。     

全球大洋季节内尺度上海-气相互作用特征分析

判定局地海-气相互作用的特征对海-气耦合模式中应用哪种形式的“强迫模拟”具有重要指导作用。本文根据海表热通量异常与海表温度异常及海表温度变率之间的相关关系,对全球大洋季节内尺度上的海-气相互作用特征进行了综合分析。结果表明:(1)南、北半球亚热带地区海-气相互作用的特征主要表现为大气对海洋的强迫,且在夏季(北半球为6—8月,南半球为12—翌年2月)强迫作用的范围最大,冬季强迫作用的范围最小;(2)赤道中、东太平洋及赤道大西洋地区海-气相互作用的特征全年表现为海洋对大气的强迫,印度洋索马里沿岸、阿拉伯海以及孟加拉湾地区仅在6—8月表现出海洋强迫大气的现象,而孟加拉湾则在9—11月表现为大气强迫海洋;(3)45°N(S)以上的高纬度地区海表温度的异常和变率无法用局地热通量的交换来解释,这是因为该区域海表温度的变化主要由平流等海洋内部动力过程决定,因此海-气之间在季节内尺度上的相互作用不明显。在某些海区,季节内尺度上的海-气相互作用关系与季节以上时间尺度的这种关系可能会有明显不同。