Effect of atmospheric turbulence on orbital angular momentum entangled state

The entangled orbital angular momentum (OAM) photons propagating across a weakly turbulent atmosphere are investigated. Here, the paper uses the single-phase screen model based on the Kolmogorov theory of turbulence, especially focuses on the influence of the backward scattering on OAM evolution. The results indicate that the backward scattering plays an important role in the analysis of OAM entanglement evolution in the turbulent atmosphere. It can not be negligible especially for higher-order OAM mode. Moreover, when OAM mode is greater than 4, entangled photon pairs composed of higher OAM modes are not more robust in turbulence within the weak scintillation regime. These results will be useful in future investigations of OAM-based optical wave propagation through turbulent atmosphere.

Contextuality in Neurobehavioural and Collective Intelligence Systems

Contextuality is often described as a unique feature of the quantum realm, which distinguishes it fundamentally from the classical realm. This is not strictly true, and stems from decades of the misapplication of Kolmogorov probability. Contextuality appears in Kolmogorov theory (observed in the inability to form joint distributions) and in non-Kolmogorov theory (observed in the violation of inequalities of correlations). Both forms of contextuality have been observed in psychological experiments, although the first form has been known for decades but mostly ignored. The complex dynamics of neural systems (neurobehavioural regulatory systems) and of collective intelligence systems (social insect colonies) are described. These systems are contextual in the first sense and possibly in the second as well. Process algebra, based on the Process Theory of Whitehead, describes systems that are generated, transient, open, interactive, and primarily information-driven, and seems ideally suited to modeling these systems. It is argued that these dynamical characteristics give rise to contextuality and non-Kolmogorov probability in spite of these being entirely classical systems.

Turbulence properties in coupled and decoupled stratocumulus-topped boundary layers

<p>In marine atmospheric boundary layer (MBL), turbulence plays an important role in vertical transport of mass, heat and moisture, which is crucial for the emergence and evolution of stratocumulus clouds. We use high resolution in situ measurements of flow velocity, temperature, humidity and liquid water content performed from the helicopter-borne platform ACTOS in the region of Eastern North Atlantic in the course of  ACORES campaign to compare turbulence properties in coupled and decoupled stratocumulus-topped boundary layer. Derived parameters include turbulence kinetic energy, its production and dissipation rates, anisotropy of the inertial range, turbulent fluxes of sensible and latent heat as well as characteristic lengthscales.</p><p>Inside the observed coupled MBL, turbulence is intensively produced by buoyancy at the cloud top and at the surface, and dissipated with equal rate across the entire layer depth. Turbulence is close to isotropic and inertial range exhibits scaling relatively close to that predicted by Kolmogorov theory. Inside the decoupled MBL properties of turbulence in the bottom sub-layer (BSL) vary from those in the cloud and sub-cloud layers, which together form upper sub-layer (USL). Transition in between the BSL and the USL is most pronounced in the gradient of specific humidity. The USL is characterized by weak buoyancy production in the cloud, strong anisotropy of turbulence and the scaling deviating from that predicted by Kolmogorov theory. In BSL, fluxes of buoyancy and latent heat decrease with height from the maximum at the surface down to about zero at the transition.</p><p>In general, results are consistent with the conceptual explanation of decoupling mechanism involving two separated zones of circulation and mixing: surface driven and cloud top driven. Our observations suggest that contrasting turbulence parameters need to be considered together with convection organization in order to properly quantify the vertical transport between ocean surface and stratocumulus cloud.</p>

Estimation of the scale lengths of turbulence from GPS single difference phase observations

<p>Signals from the Global Navigation Satellite System (GNSS) travel through the whole atmosphere and encounter fluctuations of the index of refraction. The long-term variations of the tropospheric refractive index delay the signals, whereas its random variations correlate with the phase measurements. The power spectral density of microwave phase difference can be derived from physical considerations by combining results from the Kolmogorov theory and electromagnetic wave propagation. Four different dominant noise regimes are expected. Their cutoff frequencies can be estimated with the unbiased Whittle Maximum Likelihood estimator; They provide information about the scale lengths of turbulence which are directly linked with the size of the eddies or swirling motion present in the free atmosphere. Dependencies of these parameters with the satellite geometry or the time of the day pave the way for a better comprehension of how tropospheric turbulence acts as correlating GNSS phase observations. The result is less empirical modeling of GNSS phase correlations to improve the positioning results and avoid an overestimation of their precision. We use GPS single differences from 290 m distant antenna positions recorded during two days in 2013 in a common clock experiment at the Physikalisch Technische Bundesanstalt in Braunschweig Germany to explain our methodology, based on adequate filtering of the residuals to mitigate multipath effects.</p>

Using Doppler lidar systems to detect atmospheric turbulence in Iceland

The temporal and spatial scale of atmospheric turbulence is very dynamic, requiring an adequate method to detect and monitor turbulence with high resolution. Doppler Light Detection and Ranging (lidar) systems have been used widely to observe and monitor wind velocity and atmospheric turbulence profiles. Lidar systems can provide continuous information about wind fields using the Doppler effect from emitted light signals. In this study, we use a Leosphere Windcube 200S lidar system stationed in Reykjavik, Iceland, to evaluate turbulence intensity by estimating eddy dissipation rate (EDR). For this purpose, we retrieved radial wind velocity observations from velocity azimuth display (VAD) scans to compute EDR based on the Kolmogorov theory. We compared different noise filter methods, scan strategies and calculation approaches during different selected weather conditions to assess the accuracy of our EDR estimations. The results reveal that the lidar observations can detect and quantify atmospheric turbulence with high spatial and temporal resolution, our algorithm can retrieve EDR and indicate the turbulence intensity. These results suggest that lidar observation can be of high importance for potential end-user, e.g. air traffic controllers at the local airport. The work is an important step towards enhanced aviation safety in a subpolar climate characterized by severe wind turbulence.

Constant Flux States in Anisotropic Turbulence

An elementary closure theory is used to compute the scaling of anisotropic contributions to the correlation function in homogeneous turbulence. These contributions prove to decay with wavenumber more rapidly than the energy spectrum; this property is sometimes called the “recovery of isotropy” at small scales and is a key hypothesis of the Kolmogorov theory. Although comparisons with a more comprehensive theory suggest that the present theory is too crude, its elementary character makes the scaling analysis straightforward. The analysis reveals some characteristic features of anisotropic turbulence, including “angular” energy transfer in wavevector space.

Refinement of a Previous Hypothesis of the Lyapunov Analysis of Isotropic Turbulence

The purpose of this paper is to improve a hypothesis of the previous work of N. de Divitiis (2011) dealing with the finite-scale Lyapunov analysis of isotropic turbulence. There, the analytical expression of the structure function of the longitudinal velocity differenceΔuris derived through a statistical analysis of the Fourier transformed Navier-Stokes equations and by means of considerations regarding the scales of the velocity fluctuations, which arise from the Kolmogorov theory. Due to these latter considerations, this Lyapunov analysis seems to need some of the results of the Kolmogorov theory. This work proposes a more rigorous demonstration which leads to the same structure function, without using the Kolmogorov scale. This proof assumes that pair and triple longitudinal correlations are sufficient to determine the statistics ofΔurand adopts a reasonable canonical decomposition of the velocity difference in terms of proper stochastic variables which are adequate to describe the mechanism of kinetic energy cascade.

von Kármán self-preservation hypothesis for magnetohydrodynamic turbulence and its consequences for universality

We argue that the hypothesis of preservation of shape of dimensionless second- and third-order correlations during decay of incompressible homogeneous magnetohydrodynamic (MHD) turbulence requires, in general, at least two independent similarity length scales. These are associated with the two Elsässer energies. The existence of similarity solutions for the decay of turbulence with varying cross-helicity implies that these length scales cannot remain in proportion, opening the possibility for a wide variety of decay behaviour, in contrast to the simpler classic hydrodynamics case. Although the evolution equations for the second-order correlations lack explicit dependence on either the mean magnetic field or the magnetic helicity, there is inherent implicit dependence on these (and other) quantities through the third-order correlations. The self-similar inertial range, a subclass of the general similarity case, inherits this complexity so that a single universal energy spectral law cannot be anticipated, even though the same pair of third-order laws holds for arbitrary cross-helicity and magnetic helicity. The straightforward notion of universality associated with Kolmogorov theory in hydrodynamics therefore requires careful generalization and reformulation in MHD.

Product of m-measures

M-measures have been introduced as a useful tool for probability theory on IF-events. We deal with the product of M-measures, a notion which is important for the construction of a joint observable - an analogue of a random vector in the Kolmogorov theory.