极端干旱荒漠地区大气热力边界层厚度研究

通过对以往一些野外观测事实分析,发现在极端干旱荒漠区的晴天热力大气边界层厚度远远超出了以往在其他地区发现的热力大气边界层厚度,由此提出了荒漠地区超常厚度大气热力边界层现象。并且,讨论了控制大气热力边界层形成和发展的主要物理因素,还对极端干旱荒漠地区这种超常厚度大气热力边界层现象进行了理论分析和解释,初步认为地表白天强烈加热和夜间快速冷却是极端干旱荒漠区出现超常厚度大气热力边界层的最根本原因。     

一种新型潜浮式深海地震仪的设计与试验

鉴于国内外海洋地震台网的缺乏, 本文介绍了一种面向全球海域应用的漂浮式海底地震接收系统(mobile earthquake recording in marine areas by independent divers, MERMAID)。针对潜浮式地震仪MERMAID浮标的研发过程, 建立了浮标的总体设计要求与典型工作循环流程, 设计了液压式浮力调节系统、机械结构等, 并对比分析了不同转速及负浮力下潜过程, 最后进行了实验室压力检测和千岛湖湖试。试验结果表明, 该浮标能在15MPa压力下保持良好的密封性与稳定性, 利用水听器可以有效地采集到天然地震纵波(P波), 同时计算各模块单个周期的能耗, 以验证设计指标。     

Reversing buoyancy in turbidity currents: developing a hypothesis for flow transformation and for deposit facies and architecture

A turbidity current that contains fresher or otherwise less dense water than its surroundings may initially be denser than the ambient and propagate as a bottom-hugging flow, but later reverse in buoyancy as its bulk density decreases through sedimentation to become lower than that of the ambient seawater. It is proposed that this reversal in buoyancy may be a significant mechanism controlling the structure and facies of turbiditic deposits. Buoyancy reversal followed by lofting may directly affect the relative distribution of fine and coarse material in the deposit, while buoyancy reversal itself may mediate the transformation between dilute and highly-concentrated suspension flows, particularly in distal regions, and thus lead to the formation of complex turbiditic beds: in particular, the generation of distal co-genetic debrites may be expected. Similar transformations occur within dilute pyroclastic density currents, where a mobile, basal concentrated flow, termed a surge-derived pyroclastic flow, develops through rapid sedimentation from the suspended load of the overlying surge. The physical mechanisms involved in these processes are discussed, leading to the proposal of some associated facies models; these are compared with field data from the Northern Apennines, with some striking similarities being noted as well as some differences. On the basis of this discussion, some directions are suggested for future experimental and modelling work on the topic.     

A new proposal for density salinity scale (DSS98)

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Buoyancy leads to high productivity of the Changjiang diluted water: a note

Being the mightiest river emptying into the East China Sea （ECS） and the Pacific Ocean, compounded with the large increase of nitrogen and phosphorus input due to anthropogenic activities, the Changjiang River （Yangtze River） has become a dominating source of these nutrients to the estuary. The high nutrient concentrations notwithstanding, however, outside of the estuary the high biological productivity of the Changjiang diluted water （CDW） are most probably fueled mainly by nutrient-rich subsurface waters originating from the upwelled Kuroshio waters. This is because while the buoyancy of the CDW spreads it out on the ECS continen- tal shelf, the CDW entrains subsurface waters along with the nutrients. Nutrients thus supplied are several times more than those supplied by the Changjiang River.     

小型水下自航行器自沉浮装置设计与研究

文中对水下自航行器(Autonomous Underwater Vehicle,简称AUV)的自沉浮装置进行了详细设计与研究。通过对已有的自沉浮装置方案进行对比研究,设计了以高压气体吹除压载水舱的新型自沉浮装置,该装置具有结构简单、可靠性高和可维护性好的特点,并可实现模块化设计。最后,对装置的主要设计参数进行了计算与优化。     

物理模拟实验在天然气成藏研究中的应用--以柴达木盆地北缘南八仙和马海气田成藏过程为例

物理实验模拟是研究油气运移和聚集的重要手段和方法。而天然气物理模拟实验则是一个研究相对不足而又非常重要的领域,它的操作和完善可以大大促进我国西部天然气勘探,直接影响着西气东输的国策。本文正是涉及这个领域,选取柴北缘马海、南八仙气田作为研究对象,模拟了其成藏模式,认为在西部前陆盆地天然气成藏过程中断层与不整合及输导层相比,一般是优势通道;而南八仙凝析气田的形成具有差异聚集的特点,即下盘聚气而上盘不聚气,这种现象是由多种原因造成的,包括断层本身的非均质性、圈闭幅度不足及通天断层的存在等。     

Mesoscale Variability in the Summer Arctic Boundary Layer

Observations from the summer Arctic Ocean Experiment 2001 (AOE-2001) are analysed with a focus on the interactions between mesoscale and boundary-layer dynamics. Wavelet analyses of surface-pressure variations show daylong periods with different characteristics, some featuring episodes of pronounced high-frequency surface-pressure variability, here hypothesized to be caused by trapped gravity waves. These episodes are accompanied by enhanced boundary-layer turbulence and an enhanced spectral gap, but with only minor influence on the surface stress. During these episodes, mesoscale phenomena were often encountered and usually identified as front-like features in the boundary layer, with a peak in drizzle followed by changing temperature. These phenomena resemble synoptic fronts, though they are generally shallow, shorter-lasting, have no signs of frontal clouds, and do not imply a change in air mass. Based on this analysis, we hypothesize that the root cause of the episodes with high-frequency surface-pressure variance are shallow, mesoscale fronts moving across the pack ice. They may be formed due to local-to-regional horizontal contrasts, for example, between air with different lifetimes over the Arctic or with perturbations in the cloud field causing differential cooling of the boundary layer. Thermal contrasts sharpen as the air is transported with the mean flow. The propagating mesoscale fronts excite gravity waves, which affect the boundary-layer turbulence and also seem to favour entrainment of free tropospheric air into the boundary layer.     

Spar平台与刚性立管及浮力罐耦合动力研究综述

Spar平台是深水和超深水海域中极具竞争力的平台类型。Spar平台中刚性立管顶端所需的张力由月池内部的浮力罐提供,浮力罐在水平方向由导向架支撑。平台运动过程中,浮力罐及立管与平台主体发生相对运动和相互动力作用,在水平方向上发生带有空隙效应的碰撞现象,在垂向产生库仑摩擦效应。这是一种复杂的非线性多点接触耦合动力现象,对平台主体和浮力罐的运动及性能都有着重要影响。因此,无论从平台主体设计及水动力性能方面,还是从浮力罐疲劳分析及安全性方面考虑,都有必要对Spar平台与浮力罐之间的耦合动力作用进行深入的研究。在介绍目前国际上Spar平台与浮力罐相关研究情况及进展的基础上,提出了今后研究的有关建议。     

Evolution and breaking of a propagating internal wave in stratified ocean

The evolution and breaking of a propagating internal wave are directly numerically simulated using a pseudo-spectral method. The mechanism of PSI （ parametric subharmonic instability） involved in the evolution is testified clearly. It dominates gradually in nonlinear resonant interactions. As a consequence, the energy cascades to a second plant wave packet which has lower frequencies and higher wavenumbers than that of the primary wave. With the growth of this wave packet, wave breaking occurs and causes strongly nonlinear regime, i.e. stratified turbulence. The strong mixing and intermittent of the turbulence can be learned from the evolution of the total energy and kurtosis of vorticity vs. time. Some statistic properties of the stratified turbulence are also analyzed, including the spectra of KE （kinetic energy） and PE （potential energy）. The results show that the PE spectra display a wavenumber range scaling as 0. 2 N^4ky^-3 （N is the Brunt - Vaisala frequency, k, is the vertical wavenumber）, which is called buoyancy sub-range. However, the KE spectra cannot satisfy the negative cubic law of vertical wavenumber, which have a much larger downtrend than that of the PE spectra, for the potential energy is transferred more efficiently toward small scales than the kinetic energy. The Cox number of diapycnal diffusivity is also calculated, and it shows a good consistency with the observations and deductions in the ocean interior, during the stage of the stratified turbulence maintaining a fairly active level.