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1.
Convective cloudiness in the Atlantic sector of the Arctic is considered as an atmospheric spatially self-organized convective field. Convective cloud development is usually studied as a local process reflecting the convective instability of the turbulent planetary boundary layer over a heated surface. The convective cloudiness has a different dynamical structure in high latitudes. Cloud development follows cold-air outbreaks into the areas with a relatively warm surface. As a result, the physical and morphological characteristics of clouds, such as the type of convective cloud, and their geographical localization are interrelated. It has been shown that marginal sea ice and coastal zones are the most frequently occupied by Cu hum, Cu med convective clouds, which are organized in convective rolls. Simultaneously, the open water marine areas are occupied by Cu cong, Cb, which are organized in convective cells. An intercomparison of cloud statistics using satellite data ISCCP and ground-based observations has revealed an inconsistency in the cloudiness trends in these data sources: convective cloudiness decreases in ISCCP data and increases in the groundbased observation data. In general, according to the stated hypothesis, the retreat of the sea-ice boundary may lead to an increase in the amount of convective clouds. 相似文献
2.
The intensity and spectrum of nonthermal radiation from a cloud of oppositely charged drops as a possible explanation for the anomalous UHF radio noise originating from frontal clouds have been considered. It has been shown that the noise intensity is determined by the dimensions of charged particles and the particle electrification rate, which must equal 0.1–0.3 C/s km3. The radiation spectrum in the UHF range strongly depends on the resistance of microdischarge channels between drops. The frequency dependence of the radiation agrees with experimental data if R ≤ 377 Ω, i.e., if oscillations of the discharge current appear. 相似文献
3.
Measurements of the natural extremely low-frequency (ELF) radio noise (known as Schumann resonances) in the period 1988-1989 have enabled average atmospheric noise levels and Schumann resonance parameters to be deduced. At 45 Hz, the average measured electric field was 41.6 dB·μV/m·√(Hz). It is assumed that the Schumann resonance noise field in the air-space in the vicinity of the observation point can be considered to be represented as the sum of four components, one arising from propagation over a short great-circle path, and a second representing a long great-circle path contribution, each of these having an upgoing and a downgoing part. The noise fields can then be estimated at any given depth below the ground (or sea) surface from the measured values in the air. The authors present results showing the computed fields produced in the sea from submerged horizontal electric quadrupole and vertical electric dipole man-made sources, and compare these with the subsurface atmospheric noise fields deduced from the experimental measurements 相似文献
4.
A. A. Sizov 《Physical Oceanography》2001,11(3):259-270
We study the interannual and seasonal variability of hydrometeorological fields in some regions of the Atlantic-European sector.
These low-frequency processes are analyzed depending on the index ΔP (an analog of the index of the North-Atlantic Oscillation). It is shown that the average value of the index ΔP over the winter natural synoptic season can be used for the determination of stable locations of the centre of the Azorean
maximum in 1971–1980 and 1981–1990, the typical state of cloudiness in the Atlantic-European sector, and the fields of precipitations
and atmospheric temperature in some regions of the Crimea. Typical anomalies of the fields of precipitations and atmospheric
temperature over the west and south coasts of the Crimea are described. The signs of the anomalies of precipitations in the
winter natural synoptic season are in good agreement with the signs of the corresponding anomalies of the field of cloudiness
in the Black-Sea region.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
5.
本文对有限面积噪声源产生的噪声场的空间相关特性作了讨论。分别研究了接收器处于源区域里面和外面的情形。对一浅海典型声速剖面和 Baltic海区的噪声场相关特性及噪声场强度进行了计算 ,并与无限大噪声源平面的噪声场特性作了比较。同时 ,为把连续谱考虑在内 ,引入一虚假深海底 ,用复模式和来近似计算分支割线的贡献。但当接收器远离源区域时 ,连续谱经过在下介质中的长程传播 ,衰减迅速 ,故其对噪声场的贡献可以忽略 ,而仅考虑离散简正波场的贡献。结果发现 ,有限面积源的噪声场结构无论是水平结构 ,还是垂直结构均是不均匀的 ,都依赖于接收场点的绝对位置。这与无限大噪声源平面所形成的噪声场的特性是不一样的 相似文献
6.
M. A. Tolstykh D. B. Kiktev R. B. Zaripov M. Yu. Zaichenko V. V. Shashkin 《Izvestiya Atmospheric and Oceanic Physics》2010,46(2):133-143
Simulation of the atmospheric circulation on the seasonal scale with the new version of the global semi-Lagrangian model is
considered. The new version includes land surface processes parameterization taking into account influence of the vegetation
and also freezing and melting of soil moisture. The new version also includes improved parameterization for short and long
wave radiation, cloudiness and atmospheric boundary layer. 相似文献
7.
The shipping noise properties in the deep ocean are studied. Shipping noise exhibits the strong dual-horned directionality features in the flat-seabed ocean, and its directional density can be modeled by a Von Mises distribution. With the explicit expression for the directional density function, the spatial coherence functions of shipping noise are also derived, and the relative features are studied. The research result shows that the properties of shipping noise are different from the ambient noise of other sources, and it can be used for the sonar array design. The model is well matched with the experimental result, and it can be extended to the situations when the ambient noise exhibits the dual-horned structure. 相似文献
8.
9.
多通道带乘性噪声系统观测噪声的最优估计 总被引：1，自引：0，他引：1
研究在多通道观测时观测噪声的最优估计问题。就多通道的乘性噪声为对角阵且动态噪声一步相关并与观测噪声在同时刻和过去相邻时刻也相关的复杂情况下给出了在线性最小方差意义下的观测噪声最优滤波估计算法和固定区间平滑估计算法。针对这些算法进行了仿真研究 ,仿真结果表明了算法的有效性。 相似文献
10.
研究在较弱的乘性噪声条件下系统观测噪声的最优估计问题,就乘性噪声为一般随机矩阵且各观测通道乘性噪声在同时刻相关的情形,给出了在线性最小方差意义下的观测噪声最优滤波算法和最优平滑算法。针对这些算法进行了仿真研究,仿真结果表明算法有较好的估计效果。 相似文献
11.
Yu. V. Terekhin M. V. Ivanchik V. E. Kunitsa I. L. Dergileva 《Physical Oceanography》1989,1(2):141-147
A technique for the reconstruction of the sea surface temperature (SST) fields is proposed which involves linear dual-channel methods for the atmospheric correction and four procedures of cloudiness filtration. The technique was employed for processing the IR images obtained from NOAA satellites at night in the Tropical Atlantic (36th cruise of theRV AKADEMIK VERNADSKY). Analysis of the SST charts showed the high efficiency of the technique proposed.UDK 551.465.16(261.5)Translated by Mikhail M. Trufanov. 相似文献
12.
A. A. Kordzadze A. A. Surmava D. I. Demetrashvili V. G. Kukhalashvili 《Izvestiya Atmospheric and Oceanic Physics》2007,43(6):722-730
The influence of the Caucasus relief on temporal and spatial variations in meteorological fields is investigated through the numerical integration of nonadiabatic, nonstationary, and nonlinear equations of atmospheric hydrothermodynamics. A dimensionless vertical coordinate is used. In numerical experiments, this coordinate makes it possible to approximate a real relief at a high accuracy and to take into account specific features of a complex orography of the region. The cases of flowing around the relief by large-scale westerly, easterly, northerly, and southerly background winds are modeled. The relief in the lower troposphere is shown to considerably change the spatial structures of large-scale fields of meteorological elements and to form the mesoscale structures of wind, temperature, pressure, and cloudiness that are characteristic of the Caucasus. 相似文献
13.
A. E. Aloyan A. N. Yermakov V. O. Arutyunyan 《Izvestiya Atmospheric and Oceanic Physics》2010,46(6):713-726
A combined three-dimensional numerical model of convective cloudiness with detailed microphysics and a model of the transport
of atmospheric trace gases with gas- and aqueous-phase chemistry were developed. We consider the main physical mechanisms
responsible for the formation of midsized droplet clouds and the transport of gases with differing solubility therein. Test
numerical calculations were performed to investigate the sensitivity of the cloud model to variations in input parameters,
as well as the variability of the ion composition of cloud drops with regard to their size distribution. The results of numerical
calculations are presented with a preliminary analysis. 相似文献
14.
15.
In this paper a new method for obtaining a quantitative estimate of an acoustic field consisting of a set of discrete sources and background noise is described. The method is based on theL 1 (least absolute values) norm solution to an underdetermined system of linear equations defining the Fourier transform of the signal series. Implementations of the method with either equality or inequality constraints are presented and discussed. The much faster and more compact equality constraint version with a provision for modeling the noise field is recommended in practice. Experience with real data has shown the necessity of correcting for an observed Gaussian decay on the covariances. A simple means of estimating this effect and taking it into account in the signal estimation procedure is discussed, and the implications of this effect in high-resolution beamforming are considered. The effectiveness and versatility of theL 1 method indicate that it has a useful role in high-resolution signal estimation. 相似文献
16.
A tide height measurement technique usingS -band radio waves in an oblique incidence interferometer is reviewed. Generalization of the technique is described which reduces the required bandwidth of the radio frequency adjustment and increases its efficiency. This generalization, however, introduces an ambiguity in the height determination and also requires specification of the phase shift of the radio waves specularly reflected from the sea surface. The ambiguity is shown to be easily removable given coarse information about the expected time derivative of tidal height. The influence of the phase shift which contains sea-wave information is studied analytically and requirement in its specification is evaluated to have an accuracy ofpm1deg . This corresponds to a tide height determination accuracy ofpm1 cm. The method is designed for coastal regions where a bistatic experiment geometry is feasible. 相似文献
17.
1 IntroductionCorals from the tropical oceans are the well-known paleoclimate proxies that offer both the high-resolution and multi-century record length needed forquantification of seasonal to centennial variations.Most corals build skeletons of aragonite (CaCO3) andgrow at rates of millimeters to centimeters per year(Sun et al., 2002). During growth, annual densitybands are produced in the skeleton that shows timemarkers for the development of chronologies (seeFig.1). Coral skeletons may p… 相似文献
18.
A. A. Sizov 《Physical Oceanography》1997,8(4):261-267
The paper discusses the conditions corresponding to the largest and smallest North Atlantic Oscillations (NAOs). It is shown
that in winter, when NAOs are at a minimum, the number of cyclones over the Black Sea increases. At the same time, cloudiness
in the Atlantic-European section becomes heavier, compared with the largest NAO. Heavy cloudiness over the Balkan and Karpaty
mountains, with NAO at a minimum, may imply the greater likelihood of Balkan cyclones’ penetration into the Black Sea region.
The mechanism responsible for the generation of maximum (minimum) cloudiness in the Atlantic-European section is discussed.
Translated by Vladimir A. Puchkin. 相似文献
19.
研究特征系统实现算法在模态识别过程中的噪声处理问题。特征系统实现算法为目前土木工程领域应用较为广泛的一种模态识别法。在处理实测数据时,特征系统实现算法将实测数据分解为结构真实信号和噪声信号,从而将噪声消除。分块Hankel矩阵的维数对信噪分离过程影响很大。提出当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号可以最好的分离。通过在实测信号里添加噪声(产生噪声-噪声信号),将实测信号和噪声-噪声信号识别的结果进行比较,提出了1种验证识别模态参数是否为结构真实模态的检验方法。本文应用导管架平台实例来验证提出方法的适用性。结果表明,当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号能够有效地分离,此时添加的噪声主要影响噪声信号部分。由实测信号和噪声-噪声信号识别的模态参数非常吻合。 相似文献
20.
研究带乘性噪声广义系统的观测噪声最优估计问题。在假设系统正则的情况下,针对乘性噪声为一般随机矩阵即各观测通道乘性噪声同时刻相关的情况,通过受限等价变换和状态扩维的方法,给出了线性最小方差意义下的观测噪声最优滤波算法和最优平滑估计算法。数字仿真结果表明了算法的有效性。 相似文献