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1.
本文利用南海发展与不发展低压的两组合成资料集,对比分析了两类低压在结构上的异同,并分别计算了它们的加热场和涡度收支。 结果表明,两类低压的热力和动力结构大致相似,但也存在明显差异。它们的涡度收支都主要取决于散度制造项、涡度平流项和垂直输送项,积云对流的垂直输送作用也十分重要,其中贡献最大的是散度项。这方面发展低压比不发展低压表现得更明显。  相似文献   

2.
用与文献[1]完全相同的资料,差分格式和计算方法,对8211台风就高低层环流系统、风速的垂直切变、涡度场、散度场、垂直速度场、辐射特征、温度和稳定度场、质量通量场和纬向垂直环流圈等九个方面进行了结构分析,结果发现,对这次近海台风,700-400hPa的中低层在台风发生发展过程中起的作用很大,各种条件有利于中低层扰动的发展,700hPa以下为对流性稳定,700-400hPa气层为对流性不稳定,这种层结分布,加上积云对流的质量通量的垂直辐散(合)在这一层最强,使700-400hPa的中层成为和周围环境交换属性最集中的一层;也使之成为台风发生发展的主要涡源和动力源,分析200hPa流场发现,台风发展到强盛阶段,这个等压面上在台风外围发展出多通道的辐散流出,这是发生和发展初期所没有的,所以对于8211台风,高层台风外围的辐散流出可能不是最初导致热带气旋发展的原因,而更可能是台风发展过程的结果,根据对南北风分量时间剖面图,中尺度垂直运动和积云对流质量通量随时间的变化以及纬向垂直环流圈随时间的变化等的分析,似乎也支持这种看法。  相似文献   

3.
江淮气旋是影响我国东部沿海地区的重要天气系统,为了弄清其发生发展机制,以便服务于预报,对其垂直速度场进行合理的诊断分析是其中的关键问题之一。但是对天气尺度系统的垂直速度场的计算也是当前天气研究的难点之一。计算垂直速度的方法有很多种,对诊断分析言,目前倾向于运动学方法,但采用这一方法的主要困难是如何处理测风不精确所带来的计算误差,最近不少人采用o’brien(1970)提议的方法对用实测风计算的垂直速度进行订正,它的基本思路是把最后的累积误差“均匀”分摊到各等压面层上去。本文根据Pearce(1974)的启示,从产生误差的气象原因着手,建立Spline方程,进行了垂直速度场的计算和订正,作为个例,本文用上述方法对一次江淮气旋的垂直速度场进行了分析,对照卫星云图和降水实况,结果还是令人鼓舞的。  相似文献   

4.
2005年山东半岛特大暴风雪分析   总被引:2,自引:0,他引:2  
利用常规资料及MM5模拟结果,对2005年12月3-22日山东半岛特大暴风雪过程进行分析,结果表明:此次过程发生在前期异常偏暖,而在强冷空气导致寒潮爆发的形势下,强海气温差、日本海后部横槽持续气旋性弯曲和强冷平流是大尺度环流背景,半岛北部一带850hPa气温下降到-12℃是出现大雪或暴雪的重要指标;中尺度分析的结果表明,冷流降雪的散度、垂直速度、涡度垂直结构不同于一般暴雨过程,其上升运动、高空辐散等局限在500hPa以下的对流层中低层,使冷流降雪由低云引起,为更深入了解冷流降雪的机制提供参考。  相似文献   

5.
简要介绍了准地转Q矢量分析方法,并用NCEP 1°×1°格点资料计算了Q矢量、Q矢量散度场及Q矢量锋生函数等物理量.从Q矢量流场、Q矢量散度场水平和垂直分布,及Q矢量锋生函数场分布等方面,对2005年5月5日福建前后两次飑线天气过程进行了分析.其结果表明Q矢量分析方法对强对流天气的预报具有指示作用.  相似文献   

6.
徐炳荣 《海洋学报》1984,6(3):301-310
选用海洋调查船“实践”号、“向阳红09”号在全球大气试验热带风观测(TWOS)期间的六天观测资料及同期的两个岛屿站的探空记录,计算了区域平均的大尺度参数:相当位温、水平散度、相对涡度及垂直速度的垂直分布.结合热量,湿度的收支研究计算了视热源、视湿度汇及总涡动热通量的垂直分布,据卫星云图及海面气象观测将所研究的六天分为扰动控制及信风控制两类.通过扰动及信风控制下各大尺度参数平均值的比较,并与西太平洋赤道海域、大西洋信风区的其他研究结果相比较,得到西太平洋赤道槽区大尺度扰动结构上的一些特征.  相似文献   

7.
万凯 《海洋科学进展》2005,23(3):320-327
针对中国南海ERS-2/SAR三维对流涡旋图像,分别利用Young的协方差方法和惯性子域方法,反演了对流海洋大气边界层高度、海洋大气边界层垂直对流尺度速度、表面浮力通量、Obukhov长度、稳定性校正后的海面风速和海面风速稳定性校正因子。结果表明,2种反演方法的结果符合较好,在一定程度上说明利用协方差方法和惯性子域方法从卫星SAR图像反演海洋大气边界层参数的有效性。  相似文献   

8.
山东半岛一次中β尺度暴雨的数值模拟分析   总被引:4,自引:0,他引:4  
利用NCAR/PSU的中尺度大气非静力模式MM5,对2004年8月5日发生在山东半岛的1次中β尺度暴雨过程进行了数值模拟和分析.将模拟的位势高度场、风场、降水与实况进行对比分析,在模拟结果比较合理的情况下,着重对发生暴雨的动力学机制进行了分析.结果表明:黄海中部高能区和副高边缘的高比湿带的维持造成对流不稳定,类似“干线”的特征有利于储存对流不稳定能量.在850hPa散度场上,山东半岛存在辐合辐散交替出现的链式分布,这揭示了重力波的存在;沿辐合辐散交替出现中心连线,作涡度、散度的垂直剖面,显示出重力波的垂直结构特征;重力波过程对暴雨天气的发生、发展有触发、组织和加强作用,天气尺度切变线辐合加强对重力波有激发作用.  相似文献   

9.
对山东半岛及黄海中部海域1996年6、7月份500hPa各要素T63数值预报产品的统计检验与分析得出:除了第四点散度的48h预报值外,其它各点各要素的预报值和实况值呈现很好的相关性(信度95%),且对位势高度和温度两要素来说,预报效果极佳,预报值与实况值相差甚少,由此说明,在进行山东半岛地区500hPa各要素(温度、相对湿度、位势高度、垂直速度、涡度)24h、48h预报时,T63模式的结果具有很高的参考价值而第四点散度的48h预报效果相对较差。至于该模式对陆地上的预报效果好,还是海上预报效果好,将因不同要素而异,需具体分析。  相似文献   

10.
文中将分为具有密度阶跃的两层,设务层内各物理量与深度无关,用推广的ADI方法进行包括潮流和风海流的二层流场计算,待流场计算稳定,与温度扩散方程和上均匀层深度预报方程相耦合,对黄渤海区表,底层温度和上均匀层深度作了为期4d的度报。然后,通过温度垂直剖面自模函预报出三维的水温场。  相似文献   

11.
A complication of finite-volume triangular C-grid methods is the numerical emergence of horizontal divergence errors that lead to grid-scale oscillations in vertical velocity. Nonlinear feedback via advection of momentum can lead to numerical instability in velocity modes via positive feedback with spurious vertical velocities induced by horizontal divergence truncation error. Existing strategies to mitigate divergence errors such as direct divergence averaging and increased diffusion do not completely mitigate horizontal vertical velocity oscillations. We present a novel elliptic filtering approach to mitigate this spurious error and more accurately represent vertical velocities via improved calculation of horizontal divergences. These results are applied to laminar curved channel flows, demonstrating the applicability of the method to reproduce secondary flow features.  相似文献   

12.
首先论述了航空矢量重力测量中科里奥利加速度的计算模型,给出了科里奥利加速度改正对水平、垂直速度要求的分析模型。数值表明,在低纬地区欲达到1mGal的科里奥利加速度的精度,要求速度的精度为5cm/s左右;依据实测数据,目前GPS测得的载体速度精度为0.3mm/s,完全能够满足航空矢量重力测量对科里奥利加速度改正的要求。  相似文献   

13.
A new method is presented to process and correct full-depth current velocity data obtained from a lowered acoustic Doppler current profiler (LADCP). The analysis shows that, except near the surface, the echo intensity of a reflected sound pulse is closely correlated with the magnitude of the difference in vertical shear of velocity between downcast and upcast, indicating an error in velocity shear. The present method features the use of echo intensity for the correction of velocity shear. The correction values are determined as to fit LADCP velocity to shipboard ADCP (SADCP) and LADCP bottom-tracked velocities. The method is as follows. Initially, a profile of velocity relative to the sea surface is obtained by integrating vertical shears of velocity after low-quality data are rejected. Second, the relative velocity is fitted to the velocity at 100–800 dbar measured by SADCP to obtain an “absolute” velocity profile. Third, the velocity shear is corrected using the relationship between the errors in velocity shears and echo intensity, in order to adjust the velocity at sea bottom to the bottom-tracked velocity measured by LADCP. Finally, the velocity profile is obtained from the SADCP-fitted velocity at depths less than 800 dbar and the corrected velocity shear at depths greater than 800 dbar. This method is valid for a full-depth LADCP cast throughout which the echo intensity is relatively high (greater than 75 dB in the present analysis). Although the processed velocity may include errors of 1–2 cm s−1, this method produced qualitatively good current structures in the Northeast Pacific Basin that were consistent with the deep current structures inferred from silicate distribution, and the averaged velocities were significantly different from those calculated by the Visbeck (2002) method.  相似文献   

14.
基于南海北部浮标和潜标的声学多普勒流速剖面仪(ADCP)数据,通过一套几何算法计算了台风海鸥(1415)期间ADCP的空间变化和流速误差,并进行数据校正。浮标上,台风过后ADCP的水平位移最大可达2.61 km,水平流速误差最大可达0.27 m/s,垂向流速误差最大仅为5×10-4 m/s;温跃层流速校正值在台风过后显著大于流速测值,这表明水平校正对于温跃层流速的质量控制很重要。潜标上,ADCP最大垂向位移增量为179 m,最大绳子倾角为35°,最大水平位移为1.5 km; ADCP水平流速误差和倾角误差都很小,在数据校正中可忽略不计,但对台风过后中层流速的垂向校正不能忽略。  相似文献   

15.
Mercury injection capillary pressure (MICP) is a commonly-used technique for measurements of porosity, pore throat size distribution, and injection pressure vs. mercury saturation for many types of rocks. The latter two are correlated to and can be used to estimate permeability. Problems for MICP application in mudrocks are associated with two types of system errors: conformance and compression effects. These two sources of error are well-recognized, but no standard procedures to correct them exist. In this study, a new method for conformance and compression corrections was developed, and the method applied to five Eagle Ford Shale samples. Conformance correction is based on comparison of mercury injection volume vs. pressure curves between epoxy-coated and uncoated samples. Compression correction is based on calculation of compressions before and after mercury intrusion in MICP experiment. Different types of compressions are quantified and compression corrections on porosity, pore throat size distribution, and injection pressure vs. mercury saturation are performed. Porosity and permeability were calculated based on corrected MICP data. Results show that both conformance and compression corrections are important for accurate MICP porosity calculation, whereas conformance correction is more important than compression correction in permeability calculation.  相似文献   

16.
An approximate theory is constructed to describe quasi-two-dimensional viscous incompressible flows. This theory takes into account a weak circulation in the vertical plane and the related divergence of the two-dimensional velocity field. The role of the nonlinear terms that are due to the interaction between the vortex and potential components of velocity and the possibility of taking into account the corresponding effects in the context of the concept of bottom friction are analyzed. It is shown that the nonlinear character of friction is a consequence of the three-dimensional character of flow, which results in the effective interaction of vortices with vertical and horizontal axes. An approximation of the effect of this interaction in quasi-two-dimensional equations is obtained with the use of the coefficient of nonlinear friction. The results based on this approximation are compared to the data of laboratory experiments on the excitation of a spatially periodic fluid flow.  相似文献   

17.
Based on the Boussinesq assumption,derived are couple equations of free surface elevationand horizontal velocities for horizontal irrotational flow,and analytical expressions of the correspondingpressure and vertical velocity.After the free surface elevation and horizontal velocity at a certain depth areobtained by numerical method,the pressure and vertical velocity distributions can be obtained by simplecalculation.The dispersion at different depths is the same at the O(ε)approximation.The waveamplitude will decrease with increasing time due to viscosity,but it will increase due to the matching ofviscosity and the bed slope.thus,flow is unstable.Numerical or analytical results show that the waveamplitude.velocity and length will increase as the current increases along the wave direction.but theamplitude will increase.and the wave velocity and length will decrease as the water depth decreases.  相似文献   

18.
远海航渡式水深测量水位改正方法研究   总被引:1,自引:0,他引:1  
针对远海航渡式水深测量作业中的潮汐改正难题,基于全球潮汐场DTU10模型及GPS无验潮测深两种改正模式,通过潮汐场预报精度评估、验潮站实测数据比对分析以及GPS大地高计算潮汐值等多种手段,开展了大范围、长时段、单测线情况下水深测量水位改正研究,形成了一套适用性强的航渡水深测量水位改正方法与流程,为面向全球的海洋水深测量资料处理提供了潮汐、垂直基准和水位归算的方法和技术支持。  相似文献   

19.
Free inertia-gravity internal waves are considered in a two-dimensional vertically nonuniform flow in the Boussinesq approximation. The equation for vertical velocity amplitude includes complex factors caused by the gradient of the flow velocity component transverse to the wave-propagation direction; therefore, the eigenfunction and wave frequency are complex. It is shown that the decrement of damping (imaginary correction to the frequency) of 15-min internal waves is two orders of magnitude smaller than the wave frequency; i.e., the waves weakly damp. Vertical wave fluxes of heat and salt are nonzero due to the phase shift between fluctuations of the vertical velocity and temperature (salinity) different from π 2. The vertical component of the Stokes drift speed is also nonzero and contributed into the vertical transport.  相似文献   

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