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1.
水平切变基流中惯性重力波的发展 总被引：1，自引：0，他引：1
采用分层浅水波方程组和ＷＫＢ方法，建立了在基流的水平切变和地形的影响之下惯性重力波的能量方程，由此讨论波动的发展。主要得出：在急流的气旋性环流区，曳式波发展；在反气旋性环流区，导式波发展。在山脉的南北坡，导式波和曳式波均有发展的可能。 相似文献
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切变气流中地形强迫激发的非线性长波 总被引：1，自引：0，他引：1
经推导得到了包括地形和耗散的ＦＫｄＶ－Ｂｕｒｇｅｒｓ方程,利用数值解讨论了地表强迫激发的弧波演变以及移动性孤波与地形的相互作用,结果显示,对于α〉０或α〈０,不论是在气旋式切变气流还是反气旋式切变气流中,地形都能在强迫激发出定常孤波,在其下游产生调制椭圆余弦波列的背风波,当α＝０时,在反气旋式切变气流中强迫区产生的是大振幅定常孤波,气旋式切变气流中强迫区产生的是复杂的非定常孤波,地形强迫产生的ｍ＝ 相似文献
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纬向切变基流中的非线性正压Rossby波 总被引：2，自引：0，他引：2
在半地转近似下，用相角函数方法得到了包含纬向基流及其切变的非线性常微分方程。利用常微分方程解的拓扑性质的定性理论，直接得到该方程存在有限振幅的周期波解与孤立波解即非线性正压Ｒｏｓｓｂｙ波解存在的条件，由此分析了纬向切变基流对波解存在的影响。最后利用函数逼近法求得了非线性正压Ｒｏｓｓｂｙ波解的显式表达式。结果表明，纬向切变基流对波的影响不仅表现在波的存在方面，而且还表现在波的形态方面，反映了波的非线性特点和基流对波动的作用。 相似文献
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斜压罗斯贝波非线性问题的研究 总被引：2，自引：0，他引：2
本文利用两层斜压准地转模式，讨论了波－流相互作用问题，得到以下结论：（１）当大气中基本流切变较大时，波流间能量交换明显。切变较小时，波幅变化较小；（２）在较小的基本流切变下，波动可出现稳定的平衡态，此平衡态多为相当正压状态；（３）斜压波在发展过程中，温度场和流场之间具有制约关系 相似文献
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切变东风基流和非绝热加热对热带扰动的作用 总被引：1，自引：0，他引：1
文中用斜压模式讨论了东风水平切变基流和非绝热加热对热带扰动的影响,指出:基本气流的切变有使西传波动加速,东传波动减速的倾向;切变会造成赤道Rossby波的不稳定发展;加热激发的赤道强迫波可以是垂直传播波. 相似文献
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切变基流对赤道大气波动稳定性的作用 总被引：3，自引：2，他引：3
在赤道β平面近似条件下，使用纬向切变基流下线性化Boussinesq方程组，分析了在纬向切变基流下几种赤道大气波动的稳定性特征。研究结果表明，基本气流的水平切变对赤道大气波动起到不稳定的作用，但是对赤道大气Kelvin波的频率、稳定性以及传播的相速度并不起作用。基本气流的水平切变使得相对于基本气流向东传播的重力惯性内波相速度减慢，而使得相对于基本气流向西传播的重力惯性内波的相速度加快，却造成相对于基本气流向西传播的Rossby波相速度减慢。基本气流的水平切变对于对赤道混合Rossby-重力惯性内波的影响主要取决于纬向波数k值的范围大小。当纬向波数k值较小时，基流的水平切变使得相对于基本气流向西传播的混合Rossby-重力惯性内波相速度加快；而当纬向波数k值较大时，则使得相对于基本气流向西传播的混合Rossby-重力惯性内波相速度减慢。在半地转近似下，风速水平切变的存在，会使得波长较大（纬向波数k→0）的赤道Rossby波相对于基本气流向西传播的相速度减慢；而风速垂直切变的存在，必然会引起这种波长较大（k→0）的Rossby波出现不稳定增长，同样也会造成赤道Rossby波相对于基本气流向西传播的相速度减慢。最后通过扰动发展能量方程，说明了基本气流的水平切变和垂直切变可以为扰动的发展提供能量来源。 相似文献
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本文在半地转近似下讨论了纬向切变基流中的非线性正压Ｒｏｓｓｂｙ波，给出了存在波解的切变基流条件。 相似文献
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采用分层浅水波方程组和ＷＫＢ方法，分别讨论了经向基流的垂直切变和南北走向的地形对二维惯性重力波的移速，稳定性以及发展的影响。 相似文献
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切变流中的CISK机制与惯性重力波 总被引：1，自引：0，他引：1
利用板对称，有切变的大气动力学方程组，由行波法导出非线性微分方程，通过非线性稳定性理论讨论方程的稳定性，求解了ＫＤＶ方程，并讨论了线性ＣＩＳＫ，非线性ＣＩＳＫ，惯性稳定度参数和大气风速垂切变对惯性重力孤波强度和宽度的影响，目的早通过了解影响惯性重力孤波发展的因子，更深入地理解低纬中尺度天气系统形成和发展的过程。 相似文献
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Diana J. M. Greenslade Eric W. Schulz Jeff D. Kepert Graham R. Warren 《Journal of Atmospheric & Ocean Science》2005,10(3):261-287
Recent work has demonstrated that surface marine winds from the Bureau of Meteorology's operational Numerical Weather Prediction (NWP) systems are typically underestimated by 5 to 10%. This is likely to cause significant bias in modelled wave fields that are forced by these winds. A simple statistical adjustment of the wind components is shown to reduce the observed bias in Significant Wave Height considerably. The impact of increasing the vertical resolution of the NWP model and assimilating scatterometer data into the model is assessed by comparing the resulting forecast wind and waves to observations. It is found that, in general, the inclusion of scatterometer observations improves the accuracy of the surface wind forecasts. However, most of the improvement is shown to arise from the increased number of vertical levels in the atmospheric model, rather than directly from the use of the observations. When the wave model is forced with surface winds from the NWP model that includes scatterometer data, it is found that the scatterometer assimilation does not reduce the systematic bias in surface wave forecasts, but that the random errors are reduced. 相似文献
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Comparison Between Eddy-Correlation and Inertial Dissipation Methods in the Marine Atmospheric Surface Layer 总被引：2，自引：2，他引：0
A comparison of momentum fluxes determined by the eddy-correlation method(ECM) and the inertial dissipation method (IDM) has been performed using longterm measurements over the sea. The measurements were made on the island ofÖstergarnsholm in the middle of the Baltic Sea. The results show that a`classical' form of the inertial dissipation method, i.e., assuming that the transportterms are negligible, and using an effective value for the Kolmogorov constant of0.55, can be used with a mean relative difference between the two methods of about15% for -1 < z/L < 0.5 (z being height and L the Obukhov length). The IDMmethod works best for high wind speeds and neutral conditions. For low windspeeds (U < 6 m s-1) the relation between the two methods is morecomplex. IDM then gives higher values than ECM on the average (about 20%),especially for swell conditions, indicating the need for an imbalance function inthe turbulent kinetic energy budget. Calculations of the effective Kolmogorovconstant, a, suggest a dependence upon the wave age, a increasing with increasing wave age, where the value 0.59 fits the data well for saturated waves. 相似文献
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Observations obtained over a glacier surface in a predominantlykatabatic flow and with a distinctwind maximum below 13-m height are presented. The data werecollected using a 13-m high profilemast and two sonic anemometers (at about 2.5-m and 10-m heights).The spectra at frequencies belowthat of the turbulence range appear to deviate considerably fromthe curves obtained by Kaimal andco-workers during the 1968 Kansas experiment. The characteristicsof these deviations are compared tothe observations of others in surface-layers disturbed by anykind of large-scale outer-layer (orinactive) turbulence. In our case the disturbances arelikely to be induced by the highmountain ridges that surround the glacier. Moreover, the deviationsobserved in the cospectra seemto result from an, as yet, unspecified interaction between theinactive outer-layer turbulenceand the local surface-layer turbulence. Near the distinctwind maximum turbulence production ceasedwhile turbulence itself did not, probably the result ofturbulence transport from other levels. Consequently, we studied thelocal similarity relations using w instead of u* as an alternative velocity scale. Wellbelow the wind maximum, and for relatively low stability(0< Rig <0.2), the flow behaves accordingto well established local-scaling similarity relationshipsin the stable boundary layer. For higherstability (Rig > 0.2), and near or above the wind maximum, the boundary-layer structure conforms tothat of z-less stratification suggesting that the eddy sizeis restricted by the local stability ofthe flow. In line with this we observed that the sensibleheat fluxes relate remarkably well to thelocal flow parameters. 相似文献
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C. Lafon J. Piazzola P. Forget O. Le Calve S. Despiau 《Boundary-Layer Meteorology》2004,111(2):339-360
The whitecap coverage generated by breaking waves plays a major role in the transfer of heat, momentum, water vapour and particles at the air-sea interface. The sea surface covered by whitecaps strongly depends on both the wind and the wave-field characteristics. In particular, in coastal zones, the variations of the whitecap fraction, commonly noted W, differ from open ocean conditions, due to fetch effects, wave-current interactions, bottom influence and irregular coastlines affecting both the wind properties and the wave development. We present an analysis of the whitecap-fraction variations using experimental data acquired during FETCH (Flux, Etat de mer, et Télédétection en Condition de fetcH variable), an experimental campaign that took place in the Gulf of Lion off the French Mediterranean coast in 1998. The data include various conditions of wave development associated with fetch and unsteady effects. The whitecap fraction W was measured using an original image processing technique applied to sea surface photography. Specific relationships between the whitecap fraction and both atmospheric and oceanic parameters are investigated, which confirm the suitability of the friction velocity for modelling W. However, W has also been parameterised using wave-parameter dependent relationships, which is of interest for very short fetches. 相似文献
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Csar A. Mendoza-Briceo Miguel H. Ibez Valery M. Nakariakov 《Dynamics of Atmospheres and Oceans》2001,34(2-4)
The weakly nonlinear evolution of quasi-isentropic magnetoacoustic waves in the solar atmosphere is analyzed. The plasma is assumed to be initially homogeneous, in thermal equilibrium and with a straight and homogeneous magnetic field frozen in. Additionally, the plasma is assumed to be cooled by the standard cooling function in the range of 104 K<T<107 K and heated by a mechanism which is proportional to the density and temperature. The range of temperature where the plasma is isentropically unstable, the e-folding time for thermal instability and the corresponding time and length-scale for wave breaking are found. 相似文献
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The binary water–sulphuric acid nucleation has long been considered an important path for new particle formation in the atmosphere. The formation rate depends nonlinearly on temperature and vapour concentrations. We aim to find out if atmospheric small scale and mesoscale spatial and temporal variability can increase the nucleation rate significantly. Simultaneous and separate effects of variation in temperature, humidity and sulphuric acid concentration on the mean nucleation rate have been modelled. We have assumed that the distributions of variables are Gaussian and compare the mean of simulated nucleation rates with the nucleation rate in mean conditions without variation. According to our studies the atmospheric variability can increase the mean nucleation rate by orders of magnitude but the significant effect is limited to specific conditions. The effect seems to be more important in the lower troposphere than in the upper troposphere, where temperature and sulphuric acid concentrations are lower. In addition, our model simulations indicate that the atmospheric variability can only explain part of the difference between measured and theoretically required sulphuric acid concentrations in conditions where particle formation has been observed. We have parametrised the effect of atmospheric variability as a simple correction factor for the effect of temperature and humidity variation. 相似文献
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本文利用2012～2015年西南涡加密观测大气科学实验的剑阁、金川、九龙和名山四站探空资料,统计分析了6～7月西南涡活动期间对流层中、高层（6～12 km）的重力波过程,结果表明:青藏高原东部川西高原南部的九龙站与其余三站不同,重力波源主要来自对流层上层,波能传播方向向上,剑阁、金川和名山三站重力的波源主要来自对流层下层,波能传播方向向下。重力波过程在不同类型的西南涡活动中有明显差异,在移出型西南涡活动初期,重力波水平传播方向主要为东北向,其上传概率远大于下传概率,波动的动能和潜能较大且变化剧烈;而对应源地型西南涡,初期主要呈西北—东南向传播且重力波上传与下传概率相当,动能和潜能较小且变化相对平缓同时本次研究表明,重力波水平传播方向对西南涡的移动方向也有一定指示作用。按照发生时刻本文将重力波分为日发型重力波和夜发型重力波,在夜发型西南涡初期,重力波活动夜发（北京时20:00～08:00）的概率较大,这表明重力波的夜发性与西南涡的夜发性可能存在一定关联。 相似文献
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在核安全分析和环境影响评价中,必须使用到的是小时气象数据。对自动气象站小时风向的计算方法和小时数据如何统计,地面气象规范中和核安全导则中还没有定论,因此本文对小时风向统计方法展开讨论。目前小时风向值的计算方法有算术平均法、滑动平均法、矢量平均法和频率最高法,针对算术平均法和滑动平均法对经过0°的风向统计容易出现误差,本文提出对此的修正方法并对4种计算方法进行了比较。结果表明：文中过零风向修正方法简便准确,小时数据统计方法为正点前10min数据时,修正算术平均法更可靠,但该方法对风速为零时的判断容易出现误差,因此在小风、静风频率高的地方推荐矢量平均法。关于小时数据的划分方法,美国核管会RG1.23与我国核安全导则及地面气象规范中的规定不同,因此文中利用实测资料对不同小时数据统计方法所得结果比较,分析表明,取整点前或其他时段的10min和15min的数据进行平均的风向相关矩阵一致性为97.87%;取4个15min平均值的平均或6个10min数据平均值的平均作为小时值的风向相关矩阵一致性为99.96%,这两种统计方法与取10min和15min的一致性为86.00%,相对较差;取60min时段的平均值作为小时值则与其余方法一致性最差。 相似文献