西风急流斜压不稳定的定性分析

本文使用斜压不稳定的判据和能量方程,对所设计的西风急流模式定性讨论了它的斜压不稳定性,得出了西风急流斜压不稳定的易发生区、西风急流斜压不稳定的发展机制等一些有益的结果。     

非线性Lyapunov稳定性及Stern''''s Modons的稳定性判据

本文在构造正压大气运动的浅水波模式的Hamilton守恒量和积分不变的Casimir泛函的基础上,建立了一个积分不变的Lyapunov函数,通过使用变分法,找出了正压旋转流体运动的非线性Lyapunov稳定性判据,并进一步讨论了Stern's Modons的稳定性。     

非静力平衡下中小尺度扰动的不稳定发展

本文采用非静力平衡模式,使用摄动方法研究了里查逊数与中小尺度扰动的稳定性的关系。在零级近似和一级近似下,对称不稳定判据依次为RiF;在零级近似下斜压不稳定判据为Ri<-_(k2)~8     

斜压大气中非线性ROSSBY波

本文利用位涡守恒方程,导出了斜压大气中非线性Rossby波满足KDV方程和MKDV方程,求得了斜压大气中非线性Rossby波足椭园余弦波和孤立波,并对它们的性质进行了讨论,着重用斜压Rossby立波的性质解释了大气中的一些重要天气现象如极涡、阻塞高压和切断低压。     

变分原理和大气运动的稳定性

本文通过引入守恒的伪动量(Pseudo-Momentum),并利用Hamilton函数,Casimir泛函,建立了一个新的Lyapunov泛函,在此基础上使用变分原理得到了大气运动所满足的广义稳定性判据。当基本气流仅存在经向切变时,所得到的广义稳定性判据与用经典标准模方法所得到的稳定性判据是一致的。     

关于斜压大气中超长波的垂直传播

本文利用Burser模式讨论了斜压大气中超长波的垂直传播特点发现: (1)超长波的垂直传播与纬向波数无关。 (2)超长波的垂直传播不仅与大气基本风速,大气层结有关,而且还与大气基本风速,大气层结的垂直切变有关。 (3)在稳定层结大气中,东风区不利于超长波的垂直传播,西风区有利于超长波上传。     

西南低涡移动的初步分析

从描述西南低涡运动的中尺度原始方程组出发，对低涡系统作水平分布的零阶Ｂｅｓｓｅｌ函数近似，在铅直方向上取６层斜压模式近似；导出了西南低涡移动速度的控制方程，得到了影响低涡移动的较为全面的因子，并通过对个例进行６层斜压模式的数值计算和诊断分析，找出了对低涡移动取决定性作用的决定性因子、一般影响因子、作用较小的修正因子和贡献极其在弱的不影响因子。然后分析和讨论了各因子对低涡移动作用的物理意义，为认识西南低涡移动的物理机制及用于业务预报提供参考。     

正压波和斜压波的三波共振与低频振荡

通过引进δ＝Ｈ＿１／Ｈ＿２参数，对两层模式中的正压波和斜压波（考虑了层结作用）的三波共振进行了研究，结果表明：δ叁数对三波共振条件有很大的影响；并进一步讨论了在一定初始振幅的条件下，δ参数和非线性强度对三波共振周期的影响；指出：在一定的初始振佰、δ参戮和非线性强度的条件下，大气中可以形成６０天以上的甚低频振荡及３０～６０天和准两周的低须振荡。     

大气CO2浓度非均匀分布及其对地表升温影响的研究进展与展望

在气候变化和全球治理挑战日益严峻的背景下,CO₂排放及代价评估日益受到学术界和决策者的关注。当前全球范围包括联合国政府间气候变化专门委员会（IPCC）评估在内的几乎所有研究都是基于全球平均CO₂浓度来驱动气候模式的,但基于全球CO₂平均分布设定开展模拟影响评估在学术界多有争议。首先,综述了大气CO₂非均匀分布的证据,评述了大气CO₂浓度非均匀分布与地表升温过程的互馈机制。其次,从自然和人为2个维度,梳理了大气CO₂浓度非均匀分布形成的原因,并评估了其对地表升温的影响。最后,评述了当前大气CO₂浓度非均匀分布研究中存在的问题,进一步展望了其发展趋势,为把握全球与区域碳排放现状及气候变化影响提供科学判据。     

关于中尺度对称运动的稳定性及其演变

本文首先建立了中尺度对称运动的Hamihon函数,并用变分原理导出了对称运动稳定的充分条件,然后再用Lagrange变分导出了缓变介质中对称运动的波作用量方程,这种波作用量方程与用WKB方法所得到的结果是相同的。同时,本文进一步讨论了中尺度对称扰动渡包的演变规律,并获得了对称运动发展的判据。     

Rotary spectrum analysis of tidal current in the southern Yellow Sea

A complete set of one-month Acoustic Doppler Profiler (ADP) current data at a station in the southern Yellow Sea (SYS) is analyzed using the rotary spectrum method. The results revealed different rotary properties between barotropic and baroclinic tidal currents. The barotropic and baroclinic tidal currents rotate elliptically counter-clockwise and clockwise, respectively. Meanwhile, baroclinic bottom tidal currents are almost along-isobath. The baroclinic cross-isobath velocities attenuate quickly at the bottom, implying important effects of bottom topography on the cross-isobath motions.     

Theoretical study of the effect of topographic height and width on generation of internal tides

Internal tides generated upon two-dimensional Gaussian topographies of different sizes and steepness are investigated theoretically in a numerical methodology. Compared with previous theoretical works, this model is not restricted by weak topography, but provides an opportunity to examine the influence of topography. Ten typical cases are studied using different values of height and/or width of topography. By analyzing the baroclinic velocity fields, as well as their first eight baroclinic modes, it is found that the magnitude of baroclinic velocity increases and the vertical structure becomes increasingly complex as height increases or width decreases. However, when both height and width vary, while parameter s （the ratio of the topographic slope to the characteristic slope of the internal wave ray） remains invariant, the final pattern is influenced primarily by width. The conversion rate is studied and the results indicate that width determines where the conversion rate reaches a peak, and where it is positive or negative, whereas height affects only the magnitude. High and narrow topography is considerably more beneficial to converting energy from barotropic to baroclinic fields than low and wide topography. Furthermore, parameter s, which is an important non-dimensional parameter for internal tide generation, is not the sole parameter by which the baroclinic velocity fields and conversion rate are determined.     

基于滑带完整性指标的三峡库区堆积层滑坡失稳破坏判据

滑坡稳定性评价是滑坡防治中关键问题之一,滑坡失稳破坏判据研究可为滑坡稳定性评价提供支持。为了提高滑坡稳定性评价的精度,以滑坡深部位移监测数据为基础的滑坡失稳破坏判据不失为一种有效方法。基于滑坡深部位移监测数据,引入滑带完整性指标,推导得到了滑带完整性指标与滑坡抗剪强度参数之间呈正比例关系;运用滑坡稳定性计算方法和三峡库区堆积层滑坡简化模型,获得了滑带完整性指标与滑坡的稳定性系数之间呈正比例关系。建立了考虑滑带完整性指标的三峡库区堆积层滑坡失稳破坏判据,即：当滑坡滑带土完整性指标大于滑坡滑带土完整性指标的临界值时,滑坡处于稳定状态;当滑坡滑带土完整性指标小于滑坡滑带土完整性指标的临界值时,滑坡发生失稳破坏。以三峡库区典型堆积层滑坡——五尺坝滑坡为例,通过实例分析发现该判据具备可靠性,对堆积层滑坡适用性好。研究成果表明,滑带完整性指标失稳破坏判据可以用于评价滑坡的稳定状态,为滑坡失稳破坏判据研究提供了一种新思路。     

Energetics and temporal variability of internal tides in Luzon Strait: a nonhydrostatic numerical simulation

A fully nonlinear,three-dimensional nonhydrostatic model driven by four principal tidal constituents(M2,S2,K1,and O1) is used to investigate the spatial-temporal characteristics and energetics of internal tides in Luzon Strait(LS).The model results show that,during spring(neap) tides,about 64(47) GW(1 GW=109 W) of barotropic tidal energy is consumed in LS,of which 59.0%(50.5%) is converted to baroclinic tides.About 22(11) GW of the derived baroclinic energy flux subsequently passes from LS,among which 50.9%(54.3%) flows westward into the South China Sea(SCS) and 45.0%(39.7%) eastward into the Pacific Ocean,and the remaining 16(13) GW is lost locally owing to dissipation and convection.It is revealed that generation areas of internal tides vary with the spring and neap tide,indicating different source areas for internal solitary waves in the northern SCS.The region around the Batan Islands is the most important generation region of internal tides during both spring and neap tides.In addition,the baroclinic tidal energy has pronounced seasonal variability.Both the total energy transferred from barotropic tides to baroclinic tides and the baroclinic energy flux flowing out of LS are the highest in summer and lowest in winter.     

A study on the baroclinic structure of the abyssal circulation

In this paper, the linear continuously stratified ntxiel of the abyssal circulation proposed by Pedlosky (1992) was emended to include the second order term - (γθm) in the vertical turbulent mixing pararneterization of - (ω‘θ‘）x = kvθxx- θxxx, in which kv is a vertical diffusion coefficient,and γ is the second order coefficient of turbulent mixing (or simply called γ-term and γ＜0 is only allcmed). The influence of the γ-tema on the baroclinic structure of the abyssal circulation driven by up-welling out of the abyss was investigated, It was found that the γ-term has a noticeable influence on thebaroclinic structure of the upwelling driven abyssal circulation. For uniform upwelling, it favors the baroelinic layering of the abyssal circulation in the eastern part of the basin, but prevents the layering in thewest. In addition, this parameter was found to decrease the vertically averaging meridional velocity of theabyssal circulation frcrn the west to the east on the southern boundary. For upwelling localized near theeastern boundary, the γ - term favors baroclinic layering of the abyssal circulation in the whole basin.Especially, on the southern boundary the γ - term could strengthen the vertically averaging meridional ve-loeity in the west, but gready weaken it in the east. The ntntel presented here might be considered as anextension of the Pedlosky baroclinic ntntel of the abyssal circulation.     

The baroclinic residual circulation in shallow seas

There are two different modeling approaches which have been proposed and utilized to derive residual currents: the first approach is equivalent to deducing residual currents from current-meter records using filtering techniques or time averages of time-series records to remove tidal variations; in the second approach, filters or time averages over several tidal cycles are applied to the hydrodynamic equations to generate the governing equations for residual circulation. Based on the latter, both the baroclinic dynamic models of residual circulation are proposed, of which one is a two-dimensional transport model and the other is a three-dimensional model with variable eddy viscosity. The two-dimensional transport model is a direct generalization from the barotropic model of residual circulation presented by Nihoul and Randy (1975) and Heaps (1978) to the baroclinic model. In the three-dimensional model with variable eddy viscosity, using a Sturm-Liouville system adopted in the reference [5], the nondimensional problem for residual circulation reduces to the nondimensional problem of the elevation and the expression of residual currents. It should be pointed out that both the baroclinic models developed in the present paper are confined to describe the Eulerian residual circulation only.     

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Effect of low-frequency Rossby wave on thermal structure of the upper southwestern tropical Indian Ocean

We investigate the influence of low-frequency Rossby waves on the thermal structure of the upper southwestern tropical Indian Ocean (SWTIO) using Argo profiles, satellite altimetric data, sea surface temperature, wind field data and the theory of linear vertical normal mode decomposition. Our results show that the SWTIO is generally dominated by the first baroclinic mode motion. As strong downwelling Rossby waves reach the SWTIO, the contribution of the second baroclinic mode motion in this region can be increased mainly because of the reduction in the vertical stratification of the upper layer above thermocline, and the enhancement in the vertical stratification of the lower layer under thermocline also contributes to it. The vertical displacement of each isothermal is enlarged and the thermal structure of the upper level is modulated, which is indicative of strong vertical mixing. However, the cold Rossby waves increase the vertical stratification of the upper level, restricting the variability related to the second baroclinic mode. On the other hand, during decaying phase of warm Rossby waves, Ekman upwelling and advection processes associated with the surface cyclonic wind circulation can restrain the downwelling processes, carrying the relatively colder water to the near-surface, which results in an out-of-phase phenomenon between sea surface temperature anomaly (SSTA) and sea surface height anomaly (SSHA) in the SWTIO.