潮致泥沙全沙净输运解析模式

泥沙运动作为水流和底床相互作用的纽带,是河流、河口及海岸工程研究的重要内容。在潮波作用明显的河口、海岸地区,周期性的动力作用下的泥沙运动具有往复和可逆的特征,因此研究这类水域的泥沙的净输运更具有实际的意义。基于泥沙输运和流速呈指数关系假设,建立潮流环境下的泥沙全沙净输运的解析解公式,并对该公式的计算结果和数值计算以及数学模型的结果进行了检验和验证,结果表明本研究提出的公式能较好地反应潮流环境下的泥沙净输运。由此,基于本公式采用潮流分潮调和常数可计算得到全沙净输运,并可以分析各分潮流及其相互作用与泥沙净输运的关系。研究结果显示,在受径流影响较大的半日潮河口,S2、MS4、M2三潮相互作用对全沙净输运的贡献显著高于通常的潮流不对称作用,即M2、M4的相互作用。此外,河口区域径流导致的余流对泥沙净输运的贡献不可忽略,特别是在洪季,大径流量条件下往往导致余流较大,其对泥沙净输运的贡献所占比例较大。     

Three-dimensional properties of mesoscale cyclonic warm-core and anticyclonic cold-core eddies in the South China Sea

In general, a mesoscale cyclonic (anticyclonic) eddy has a colder (warmer) core, and it is considered as a cold (warm) eddy. However, recently research found that there are a number of “abnormal” mesoscale cyclonic (anticyclonic) eddies associated with warm (cold) cores in the South China Sea (SCS). These “abnormal” eddies pose a challenge to previous works on eddy detection, characteristic analysis, eddy-induced heat and salt transports, and even on mesoscale eddy dynamics. Based on a 9-year (2000–2008) numerical modelling data, the cyclonic warm-core eddies (CWEs) and anticyclonic cold-core eddies (ACEs) in the SCS are analyzed. This study found that the highest incidence area of the “abnormal” eddies is the northwest of Luzon Strait. In terms of the eddy snapshot counting method, 8 620 CWEs and 9 879 ACEs are detected, accounting for 14.6% and 15.8% of the total eddy number, respectively. The size of the “abnormal” eddies is usually smaller than that of the “normal” eddies, with the radius only around 50 km. In the generation time aspect, they usually appear within the 0.1–0.3 interval in the normalized eddy lifespan. The survival time of CWEs (ACEs) occupies 16.3% (17.1%) of the total eddy lifespan. Based on two case studies, the intrusion of Kuroshio warm water is considered as a key mechanism for the generation of these “abnormal” eddies near the northeastern SCS.     

IGS分析中心轨道综合算法实现及精度分析

针对IGS轨道综合原理,利用自编算法对IGS各分析中心2014-07~2015-07精密轨道进行综合,获得GPS综合轨道,为我国北斗系统中GEO/IGSO/MEO的轨道组合方法提供参考。结果表明,使用分析中心SIO和不使用SIO综合获得的轨道精度最大三维RMS差异可达4 mm,GPS 1 807周后加入分析中心SIO综合,综合轨道整体精度提高近50%;使用不同的坐标框架统一方法进行轨道综合,精度差异明显,利用单天SINEX旋转参数统一坐标参考框架优于利用ERP参数旋转统一坐标参考框架的方法;最后,使用本文算法计算得到的1 a轨道结果与IGS综合轨道作比较,两者三维差异小于3 mm,RMS均值为1.50 mm,根据各卫星精度因子计算的加权RMS均值为1.16 mm,证明了本文算法的精度和稳定性。     

Three-dimensional characteristics of mesoscale eddies simulated by a regional model in the northwestern Pacific Ocean during 2000–2008

Mesoscale eddies play vital roles in ocean processes. Although previous studies focused on eddy surface features and individual three-dimensional (3D) eddy cases in the northwestern Pacific Ocean, the analysis of unique eddy 3D regional characteristics is still lacking. A 3D eddy detection scheme is applied to 9 years (2000–2008) of eddy-resolving Regional Ocean Modeling System (ROMS) output to obtain a 3D eddy dataset from the surface to a depth of 1 000 m in the northwestern Pacific Ocean (15°–35°N, 120°–145°E). The 3D characteristics of mesoscale eddies are analyzed in two regions, namely, Box1 (Subtropical Countercurrent, 15°–25°N, 120°–145°E) and Box2 (Southern Kuroshio Extension, 25°–35°N, 120°–145°E). In Box1, the current is characterized by strong vertical shear and weak horizontal shear. In Box2, the current is characterized by the strong Kuroshio, topographic effect, and the westward propagation of Rossby waves. The results indicate the importance of baroclinic instability in Box1, whereas in Box2, both the barotropic and baroclinic instability are important. Moreover, the mesoscale eddies’ properties in Box1 and Box2 are distinct. The eddies in Box1 have larger number and radius but a shorter lifetime. By contrast, Box2 has fewer eddies, which have smaller radius but longer lifetime. Vertically, more eddies are detected at the subsurface than at the surface in both regions; the depth of 650 m is the turning point in Box1. Above this depth, the number of cyclonic eddies (CEs) is larger than that of anticyclonic eddies (AEs). In Box2, the number of CEs is dominant vertically. Eddy kinetic energy (EKE) and mean normalized relative vorticity in Box2 are significantly higher than those in Box1. With increasing depth, the attenuation trend of EKE and relative vorticity of Box1 become greater than those of Box2. Furthermore, the upper ocean (about 300 m in depth) contains 68.6% of the eddies (instantaneous eddy). Only 16.6% of the eddies extend to 1 000 m. In addition, about 87% of the eddies are bowl-shaped eddies in the two regions. Only about 3% are cone-shaped eddies. With increasing depth of the eddies, the proportion of bowl-shaped eddies gradually decreases. Conversely, the cone- and lens-shaped eddies are equal in number at 700–1 000 m, accounting for about 30% each. Studying the 3D characteristics of eddies in two different regions of the northwestern Pacific Ocean is an important stepping stone for discussing the different eddy generation mechanisms.     

东海黑潮温度锋的三维结构特征分析

结合卫星遥感海表温度、三维再分析温度资料和数值模拟结果,研究了东海黑潮温度锋从海表到底层的三维结构特征.结果 表明:东海黑潮海表温度锋在冬季和春季较强,秋季次之,夏季消失.多年平均的东海黑潮海表温度锋区范围主要在70～700m水深区域,温度锋的中心线与黑潮的流轴大致平行,在济州岛以南的黑潮中段区域有北上的分支.受台湾暖...     

台湾岛西南部一个暖涡的跨海盆粒子输运

台湾岛西南部是暖涡产生的源地之一, 以往的研究集中于讨论暖涡本身的运动特征和规律, 如暖涡的半径、产生位置、寿命、移动路径等, 暖涡生成机制也引发了深入的研究和探讨, 但关于该地区暖涡导致的物质输运, 仅有少量的观测且结果较为离散。文章通过AVISO(Archiving Validation and Interpretation of Satellite Oceanographic Data)卫星高度计的地转流场、海表高度异常数据以及区域海洋环流模式(ROMS)结果, 得到一个暖涡从2003年秋季至2004年春季的生消过程, 并在涡旋内10m、50m、100m层各放入10000个示踪粒子, 追踪它们的运动轨迹, 从而讨论暖涡的跨海盆粒子输运特征。该暖涡的寿命为121d, 平均半径50.4km, 移动路程1437.5km, 平均移动速度 13.5cm·s^-1。研究表明, 该暖涡具有较好的物质保守性, 可以将大部分的粒子裹挟在涡旋内部并携带着沿1000~2000m等深线向西南方向运动, 在该暖涡的消亡阶段, 由于地形的阻隔以及与流的相互作用, 涡的不稳定性和形变增加, 大量的粒子被甩出涡旋, 最后仅有18.6%~35.6%粒子随暖涡运动至海南岛南部。尽管这个比例并不大, 但涡致输运的积累作用不容小觑。示踪粒子的数目与位涡具有较好的相关性, 相关系数为0.63, 暖涡内的物质被位涡线裹挟着前行。示踪粒子在暖涡内呈螺旋状下沉, 大部分粒子在释放后的5d内基本在起始的深度上下浮沉, 仅有3.9%的粒子沉降至15m以下。在10m、50m和100m层释放的粒子平均深度最大值分别为48.7m、88.7m和130.6m。     

GLONASS inter-frequency phase bias rate estimation by single-epoch or Kalman filter algorithm

GPS Solutions - GLONASS double-differenced (DD) ambiguity resolution is hindered by the inter-frequency bias (IFB) in GLONASS observation. We propose a new algorithm for IFB rate estimation to...