基于卫星高度计的北极海冰厚度变化研究

A modified algorithm taking into account the first year(FY) and multiyear(MY) ice densities is used to derive a sea ice thickness from freeboard measurements acquired by satellite altimetry ICESat(2003–2008). Estimates agree with various independent in situ measurements within 0.21 m. Both the fall and winter campaigns see a dramatic extent retreat of thicker MY ice that survives at least one summer melting season. There were strong seasonal and interannual variabilities with regard to the mean thickness. Seasonal increases of 0.53 m for FY the ice and 0.29 m for the MY ice between the autumn and the winter ICESat campaigns, roughly 4–5 month separation, were found. Interannually, the significant MY ice thickness declines over the consecutive four ICESat winter campaigns(2005–2008) leads to a pronounced thickness drop of 0.8 m in MY sea ice zones. No clear trend was identified from the averaged thickness of thinner, FY ice that emerges in autumn and winter and melts in summer. Uncertainty estimates for our calculated thickness, caused by the standard deviations of multiple input parameters including freeboard, ice density, snow density, snow depth, show large errors more than 0.5 m in thicker MY ice zones and relatively small standard deviations under 0.5 m elsewhere. Moreover, a sensitivity analysis is implemented to determine the separate impact on the thickness estimate in the dependence of an individual input variable as mentioned above. The results show systematic bias of the estimated ice thickness appears to be mainly caused by the variations of freeboard as well as the ice density whereas the snow density and depth brings about relatively insignificant errors.     

Origin and anatomy of two different types of mass–transport complexes: A 3D seismic case study from the northern South China Sea margin

Integration of 2D and 3D seismic data from the Qiongdongnan Basin along the northwestern South China Sea margin has enabled the seismic stratigraphy, seismic geomorphology and emplacement mechanisms of eight separate, previously undocumented, mass–transport complexes (MTCs) to be characterized. These eight MTCs can be grouped into two types:(1) Localized detached MTCs, which are confined to submarine canyons and cover hundreds of km², consist of a few tens of km³ remobilized sediments and show long striations at their base. They resulted from small-scale mass-wasting processes induced by regional tectonic events and gravitational instabilities on canyon margins.(2) Regional attached MTCs, which occur within semi-confined or unconfined settings and are distributed roughly perpendicular to the strike of the regional slope. Attached MTCs occupy hundreds to thousands of km² and are composed of tens to hundreds of km³ of remobilized sediments. They contain headwall escarpments, translated blocks, remnant blocks, pressure ridges, and basal striations and cat-claw grooves. They were created by large-scale mass-wasting processes triggered by high sedimentation rates, slope oversteepening by shelf-edge deltas, and seismicity.Our results show that MTCs may act as both lateral and top seals for underlying hydrocarbon reservoirs and could create MTC-related stratigraphic traps that represent potential drilling targets on continental margins, helping to identify MTC-related hydrocarbon traps.     

基于GPS反射信号技术的渤海海冰实验

传统的海冰检测手段都存在着受天气影响或实时检测成本太高的缺点,为了更实时有效的检测海冰,减轻海冰灾害对于我国的影响,并达到防灾减灾的目的,本文研究了GPS反射信号(GPS-R)技术检测海冰的可能性。通过对2013年2月下旬在中国天津渤海湾的岸基架设GPS信号接收机所接收的观测数据进行分析,使用不同特性的反射海域(几乎全为海水或是海冰)的数据进行比对分析,其结果显示极化比值(反射左旋信号与直射右旋信号的比值)能够明显反演海冰密集度。本文首次将GPS-R技术应用于国内自主设计的渤海海冰检测实验中。     

海冰对北极海冰边缘区大洋光学观测的影响评估

Diffuse attenuation coefficient(DAC) of sea water is an important parameter in ocean thermodynamics and biology, reflecting the absorption capability of sea water in different layers. In the Arctic Ocean, however, sea ice affects the radiance/irradiance measurements of upper ocean, which results in obvious errors in the DAC calculation. To better understand the impacts of sea ice on the ocean optics observations, a series of in situ experiments were carried out in the summer of 2009 in the southern Beaufort Sea. Observational results show that the profiles of spectral diffuse attenuation coefficients of seawater near ice cover within upper surface of 50 m were not contaminated by the sea ice with a solar zenith angle of 55°, relative azimuth angle of 110°≤φ≤115° and horizontal distance between the sensors and ice edge of greater than 25 m. Based on geometric optics theory, the impact of ice cover could be avoided by adjusting the relative solar azimuth angle in a particular distance between the instrument and ice. Under an overcast sky, ice cover being 25 m away from sensors did not affect the profiles of spectral DACs within the upper 50 m either. Moreover, reliable spectral DACs of seawater could be obtained with sensors completely covered by sea ice.     

HY-2 扫描辐射计风速数据产品与平台基观测数据的比较研究

基于南海北部PY30-1平台上2012年2月至9月测风仪观测的风速数据,开展了HY-2扫描辐射计风速数据比较研究。选取时空匹配窗口为5 min和25 km,利用HY-2扫描辐射计RM 100,70和35 km分辨率3种风速数据,分别与平台观测数据进行了比较。比较结果表明:在南海北部海域,HY-2扫描辐射计100 km分辨率风速和平台观测风速的均方根偏差为3.86 m/s;70 km分辨率风速和平台观测风速的均方根偏差为10.52 m/s;35 km分辨率风速和平台观测风速的均方根偏差为5.54 m/s。还进一步比较了有雨和无雨两种情况下HY-2扫描辐射计和平台数据的偏差,结果表明:有雨和无雨条件下都是100 km分辨率的数据偏差最小。这为在我国南海北部海域应用HY-2扫描辐射计的风速数据产品的选择提供了依据。     

近50年来杭州湾七姊八妹列岛海域海床演变分析

七姊八妹列岛海域位于杭州湾南部的灰鳖洋内,除了岛礁周围局部存有深沟外,其余地区海床平缓.为了探究该海域海床演变情况,在了解杭州湾来水来沙特征基础上,分析了七姊八妹列岛海域的水动力、悬沙和底质分布特征.不同时期海图的对比分析表明,该海域近岸水深较小,人类活动频繁,围涂筑堤工程较多,一直处于淤积状态,属淤涨型岸滩,而离岸较远的海域,泥沙难于落淤而随潮反复搬运,基本处于冲淤平衡状态.1962～2008年这46 a间,七姊八妹列岛海域总体呈现与岸线走向一致的淤积、冲刷间隔分布的冲淤带.平均淤积厚度约2.2 m,淤积幅度约5.0 cm/a,大多数地方平均冲刷厚度约2.4 m,冲刷幅度约5.0 cm/a.这些特点与当地的水动力条件和泥沙沉积特性相一致.     

海杂波微弱目标分形检测

The target on the sea surface is complex and difficult to detect due to the interference of backscattered returns from the sea surface illuminated by the radar pulse. Detrended fluctuation analysis （DFA） has been used successfully to extract the time-domain Hurst exponent of sea-clutter series. Since the frequency of the sea clutter mainly concentrates around Doppler center so that we consider to extract frequency-do- main fractal characterization and then detect a weak target within sea clutter by using the difference of frequency-domain fractal characterization. The generalized detrended fluctuation analysis （GDFA） is more flexible than traditional DFA owing to its smoothing action for the clutters. In this paper, we apply the GDFA to evaluate the generalized Hurst exponent of sea-clutter series in the frequency domain. The difference of generalized Hurst exponents between different sea-clutter range bins would be used to determine whether the target exists. Moreover, some simulations with the real IPIX radar data have also been demonstrated in order to suooort this conclusion.     

福建沿海年平均海平面年际、年代际变化特征及预测

利用福建沿海4个验潮站实测潮位资料,在分析实测资料变化趋势的基础上,采用谱分析的方法分析年平均海平面的变化趋势,得到了4个站年平均海平面变化模型,并对未来50年福建沿海的海平面上升趋势进行预测。     

一种统计技术结合动力释用的沿海海雾预报方法

提出了一种利用历史相似个例查询技术,结合WRF模式输出释用的Gultepe沿海大雾业务预报方法。该方法可以较好的计算近地面大气中的液态水含量(LWC)和云滴粒子数密度(Nd)参数。利用该方法对2011—2013年的3—6月的历史沿海海雾个例进行试报,结果表明,恰当的结合统计方法和动力模式可以一定程度上克服目前数值模式不成熟的缺陷,从而提高WRF模式在大雾业务预报方面的释用水平。