Deterministic Transfer Research Articles

Regional co‐variability and teleconnection patterns in surface solar radiation on a planetary scale

AbstractThe spatial and temporal distribution of the downward solar radiation (DSR) at the Earth's surface, which is a key parameter for the Earth‐atmosphere climate system, is studied on a global scale by applying the multivariate statistical method of factor analysis (FA) on mean monthly DSR values for the period 1984–2000 for winter and summer. DSR fluxes have been computed with a physical deterministic radiation transfer model, which uses satellite and reanalysis climatological input data. FA objectively groups grid points with common temporal variability of solar radiation, identifying areas with characteristic solar radiation variability and revealing teleconnection patterns. The globally distributed DSR exhibits strong variability and can be represented by about 30 factors (sub‐areas) explaining approximately 85% of the total variance. The main factors are located in the tropical Pacific (El Niño Southern Oscillation), the northern Pacific (Aleutian low), desert areas (Africa, Middle East, and Australia), and oceanic areas (storm track zone around 60°S). Furthermore, some of these areas are teleconnected indicating common DSR variability in remote places of the Earth. The primary physical parameter for the co‐variability of surface solar radiation is found to be cloud cover. The time series of the factor scores (solar radiation) exhibit features associated with natural climatic phenomena (e.g. NAO, ENSO), thus revealing that DSR might be considered as an indirect indicator for these phenomena. On the other hand, DSR determines these phenomena through its effects on major climate parameters such as surface temperature or evaporation, thus playing a key role in their formation and explanation. Finally, our analysis revealed some statistically significant trends of solar radiation, for example, a reduction in the northern Pacific and an increase in tropical and subtropical regions, which are important for global dimming/brightening and associated surface warming of the Earth. Copyright © 2009 Royal Meteorological Society

Deterministic Generation of Quantum State Transfer Between Spatially Separated Single Molecule Magnets

We propose a new scheme for realizing deterministic quantum state transfer (QST) between two spatially separated single molecule magnets (SMMs) with the framework of cavity quantum electrodynamics (QED). In the present scheme, two SMMs are trapped in two spatially separated optical cavities coupled by an optical fiber. Through strictly numerically simulating, we demonstrate that our scheme is robust with respect to the SMMs' spontaneous decay and fiber loss under the conditions of dispersive SMMs-field interaction and strong coupling of cavity fiber. In addition, we also discuss the influence of photon leakage out of cavities and show that our proposal is good enough to demonstrate the generation of QST with high fidelity utilizing the current experimental technology. The present investigation provides research opportunities for realizing QST between solid-state qubits and may result in a substantial impact on the progress of solid-state-based quantum communications network.

Deterministic Transfer for an Unknown Atomic Entangled State via Cavity QED

We present a physics scheme for transferring an unknown atomic entan- gled state via cavity QED. In the transfer process the interaction between atoms and a single-mode nonresonant cavity with the assistance of a strong classical driving field (substitute) replace the Bell-state measurements. The scheme is insensitive to both the cavity decay and the thermal field. In addition, the success probability can reach 1.0 in our scheme. PACS: 03.67.-a, 03.67.Hk.

Teleportation of composite systems for communication and information processing

We describe two protocols for efficient data transmission using a single passive bus. Different types of interactions are obtained enabling the deterministic transfer and teleportation of composite quantum systems for arbitrary subsystem dimension and for arbitrary numbers of subsystems. The subsystems may become entangled in the transmission in which case the protocols can serve generalized teleportation based information processing as well as storage and transmission functions. We explore the cases of two qubits and two qutrits in detail, obtaining a maximally entangling mapping of the composite systems and discuss the use of a continuous variable bus.

Analog Grover search by adiabatic passage in a cavity-laser-atom system

A physical implementation of the adiabatic Grover search is theoretically investigated in a system of $N$ identical three-level atoms trapped in a single-mode cavity. Some of the atoms are marked through the presence of an energy gap between their two ground states. The search is controlled by two partially delayed lasers which allow a deterministic adiabatic transfer from an initially entangled state to the marked states. Pulse schemes are proposed to satisfy the Grover speedup either exactly or approximately, and the success rate of the search is calculated.

Analysis of vector radiative transfer through a finite slab of a stochastic precipitation medium

The formulation and solution of the vector radiative transfer equation in a finite slab of a stochastic precipitation medium of binary rain rates are considered. The electromagnetic wave is supposed to encounter alternating layered segments of the two precipitation media, each with a deterministic rain rate. Both the backscattering coefficient and the bistatic coefficient are derived by taking an ensemble average of the iterative solution for the deterministic vector radiative transfer equation. Computer simulations are given to verify the solutions via the Monte Carlo method, to feature the distinctiveness of stochastic precipitation systems, and to illustrate the relationship between the stochastic parameters and the final results. It is also concluded from the computer simulations that a finite slab of a stochastic precipitation medium could be treated as an average rain-rate precipitation layer with an acceptable approximation.

Deterministic quantum state transfer from an electronic charge qubit to a photonic polarization qubit

Building on an earlier proposal for the production of polarization-entangled microwaves by means of intraband transitions in a pair of quantum dots, we show how this device can be used to transfer an unknown single-qubit state from electronic charge to photonic polarization degrees of freedom. No postselection is required, meaning that the quantum state transfer happens deterministically. Decoherence of the charge qubit causes a nonmonotonic decay of the fidelity of the transferred state with an increasing decoherence rate.

Optimal Deterministic Transfer Function Modelling in the Presence of Serially Correlated Noise

This article addresses the development of predictive transfer function models for nonlinear dynamic processes under serially correlated model error. This work is presented in the context of the block-oriented exact solution technique (BEST) for multiple input, multiple output (MIMO) processes proposed by Bhandari and Rollins (2003) for continuous-time modelling and Rollins and Bhandari (2004) for constrained discrete-time modelling. This work proposes a model building methodology that is able to separately determine the steady state, dynamic and noise model structures. It includes a pre-whitening procedure that is affective for the general class of discrete ARMA(p, q) noise (Box and Jenkins, 1976). The proposed method is demonstrated using a simulated physical system and a real physical system.

Self-averaging radiative transfer for parabolic waves

A systematic derivations of self-averaging scaling limits of parabolic waves in terms of the Wigner distribution function is presented. The convergence of the Wigner distribution to one of the six deterministic radiative transfer equations is established. One of the main contributions of this Note is a unified framework for space–time scaling limits that lead to radiative transfer. To cite this article: A.C. Fannjiang, C. R. Acad. Sci. Paris, Ser. I 342 (2006).

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984-2000

Abstract. A decadal-scale trend in the tropical radiative energy budget has been observed recently by satellites, which however is not reproduced by climate models. In the present study, we have computed the outgoing shortwave radiation (OSR) at the top of atmosphere (TOA) at 2.5° longitude-latitude resolution and on a mean monthly basis for the 17-year period 1984-2000, by using a deterministic solar radiative transfer model and cloud climatological data from the International Satellite Cloud Climatology Project (ISCCP) D2 database. Anomaly time series for the mean monthly pixel-level OSR fluxes, as well as for the key physical parameters, were constructed. A significant decreasing trend in OSR anomalies, starting mainly from the late 1980s, was found in tropical and subtropical regions (30° S-30° N), indicating a decadal increase in solar planetary heating equal to 1.9±0.3Wm-2/decade, reproducing well the features recorded by satellite observations, in contrast to climate model results. This increase in solar planetary heating, however, is accompanied by a similar increase in planetary cooling, due to increased outgoing longwave radiation, so that there is no change in net radiation. The model computed OSR trend is in good agreement with the corresponding linear decadal decrease of 2.5±0.4Wm-2/decade in tropical mean OSR anomalies derived from ERBE S-10N non-scanner data (edition 2). An attempt was made to identify the physical processes responsible for the decreasing trend in tropical mean OSR. A detailed correlation analysis using pixel-level anomalies of model computed OSR flux and ISCCP cloud cover over the entire tropical and subtropical region (30° S-30° N), gave a correlation coefficient of 0.79, indicating that decreasing cloud cover is the main reason for the tropical OSR trend. According to the ISCCP-D2 data derived from the combined visible/infrared (VIS/IR) analysis, the tropical cloud cover has decreased by 6.6±0.2% per decade, in relative terms. A detailed analysis of the inter-annual and long-term variability of the various parameters determining the OSR at TOA, has shown that the most important contribution to the observed OSR trend comes from a decrease in low-level cloud cover over the period 1984-2000, followed by decreases in middle and high-level cloud cover. Note, however, that there still remain some uncertainties associated with the existence and magnitude of trends in ISCCP-D2 cloud amounts. Opposite but small trends are introduced by increases in cloud scattering optical depth of low and middle clouds.

Inherent Ambiguity of Languages Generated by Spine Grammars

There have been many arguments that the underlying structure of natural languages is beyond the descriptive capacity of context-free languages. A well-known example is tree adjoining grammars; less common are spine grammars, linear indexed grammars, head grammars, and combinatory categorial grammars. It is known that these models of grammars have the same generative power of string languages and fall into the class of mildly context-sensitive grammars. For an automaton, it is known that the class of languages accepted by transfer pushdown automata is exactly the class of linear indexed languages. In this paper, deterministic transfer pushdown automata is introduced. We will show that the language accepted by a deterministic transfer pushdown automaton is generated by an unambiguous spine grammar. Moreover, we will show that there exists an inherently ambiguous language.

On the decadal increase in the tropical mean outgoing longwave radiation for the period 1984-2000

Abstract. In the present paper, we have calculated the outgoing longwave radiation at the top of the atmosphere (OLR at TOA) using a deterministic radiation transfer model, cloud data from ISCCP-D, and atmospheric temperature and humidity data from NCEP/NCAR reanalysis, for the seventeen-year period 1984-2000. We constructed anomaly time-series of the OLR at TOA, as well as of all of the key input climatological data, averaged in the tropical region between 20°N and 20°S. We compared the anomaly time-series of the model calculated OLR at TOA with that obtained from the ERBE S-10N (WFOV NF edition 2) non-scanner measurements. The model results display very similar seasonal and inter-annual variability as the ERBS data, and indicate a decadal increase of OLR at TOA of 1.9±0.2Wm-2/decade, which is lower than that displayed by the ERBS time-series (3.5±0.3Wm-2). Analysis of the inter-annual and long-term variability of the various parameters determining the OLR at TOA, showed that the most important contribution to the observed trend comes from a decrease in high-level cloud cover over the period 1984-2000, followed by an apparent drying of the upper troposphere and a decrease in low-level cloudiness. Opposite but small trends are introduced by a decrease in low-level cloud top pressure, an apparent cooling of the lower stratosphere (at the 50mbar level) and a small decadal increase in mid-level cloud cover.

A finite element–spherical harmonics model for radiative transfer in inhomogeneous clouds: Part I. The EVENT model

We present a new numerical radiative transfer model for application to solar radiation transport in three-dimensional (3D) cloudy atmospheres. The code uses the finite element–spherical harmonics (FE– P N ) approximation to solve the second-order even-parity form of the transport equation. It is validated by comparison with solutions from two well-established, deterministic radiative transfer models, the one-dimensional (1D) DISORT code and the spherical harmonics discrete ordinates method (SHDOM). The cases solved show generally good agreement, but also reveal some differences. EVEn-parity Neutral particle Transport (EVENT) is very efficient at performing 1D calculations quickly and, even for quite high angular resolutions, is faster. EVENT also has a competitive speed for the simpler, less-heterogeneous multidimensional cases but it is slower than SHDOM for more variable cases. However, there is significant potential to improve the performance of EVENT; it has not yet been optimised for speed and, as such, is not a finished product. Even as it is, EVENT could be used to produce fast, lower-resolution estimates for applications where this would be sufficient, or at lower-spatial resolutions with partial homogenisation. Another difference between the models is that the SHDOM algorithm is designed for small-scale inhomogeneous cloud fields in which the grid spacing is comparable to the mean free path. Problems arise from the use of larger grid cell optical depths, with an increase in the number of iterations required and a lack of flux conservation. Neither of the models is specifically constrained to conserve flux, but the conservation of flux gives an indication of the accuracy of the solution. Increasing the spatial and angular resolution can improve the accuracy but this is not always possible for very large 3D scenes. The grid-point method of property definition in SHDOM means that it performs best for cases with a continuous variation in extinction as this avoids discontinuities in the source function. The finite clouds used in our tests have sharp boundaries that are easily defined in EVENT but the difficulties caused by these in SHDOM are evident in excesses of up to 10 fluxes. The EVENT mesh resolution is determined by the local optical depth; it has no problem in dense areas but has more trouble in coping with voids or optically thin regions. These conditions are easily handled in SHDOM through streaming of photons along discrete ordinates but EVENT must implement methods such as a ray-tracing algorithm. Cases with extreme values of the extinction coefficient are probably best avoided with EVENT, but slightly larger-scale cases with greater optical depths, not suitable for SHDOM, may be solved more easily. These factors should be considered when selecting the most appropriate method for a particular application.

Global distribution of aerosol direct radiative forcing in the ultraviolet and visible arising under clear skies

A deterministic atmospheric spectral radiative transfer model, that uses comprehensive climatological data, is developed to compute the global distribution of mean monthly clear-sky total direct aerosol radiative forcing in the ultraviolet (UV) and visible, between 0.2–0.85 μm, at the top of the atmosphere (TOA), within the atmosphere and at the Earth’s surface for winter and summer conditions. The aerosol data were taken from the Global Aerosol Data Set (GADS), given for various fixed relative humidity values and for 11 wavelengths within the UV—visible range, both for natural and anthropogenic aerosols. We first derive global climatologies of extinction aerosol optical thickness (AOT), single-scattering albedo (<em>ω</em>_aer) and asymmetry factor (<em>g</em>_aer), for actual relative humidity values within the aerosol layer, based on the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) Reanalysis Project and the Tiros Operational Vertical Sounder (TOVS) datasets. We include the global distribution of cloud cover using the D2 data from the International Satellite Cloud Climatology Project (ISCCP), to define the clear-sky fraction at the pixel level for each month. Supplementary 10-yr climatological data for surface and atmospheric parameters were taken from NCEP/NCAR, ISCCP-D2 and TOVS. Our present analysis allows the aerosol radiative properties and forcings to vary with space, time and wavelength. The computed mean annual global AOT, <em>ω</em>_aer and <em>g</em>_aer values are found to be 0.08, 0.96 and 0.73, respectively, at 0.5 μm. On a mean monthly 2.5° pixel resolution, aerosols are found to decrease significantly the downward and the absorbed solar radiation at the surface, by up to 28 and 23 W m⁻², respectively, producing a surface cooling at all latitudes in both winter and summer. Aerosols are found to generally increase the outgoing solar radiation at TOA (planetary cooling) while they increase the solar atmospheric absorption (atmospheric warming). However, the model results indicate that significant planetary warming, by up to 5 W m⁻², can occur regionally, such as over desert areas, due to strong aerosol absorption. A smaller planetary warming (by up to 2 W m⁻²) is also found over highly reflecting ice- or snow-covered areas, such as Antarctica and Greenland, as well as over Eastern Europe, Siberia and North America. In general, the aerosol-induced surface cooling exceeds the induced atmospheric warming, except for regions characterized by strong aerosol absorption (e.g. deserts). On a mean annual global basis, natural plus anthropogenic aerosols are found to cool the Earth by 0.6 W m⁻² (they increase the planetary albedo by 0.28%), to heat the atmosphere by 0.8 W m⁻², while they decrease the downward and net surface solar radiation (surface cooling) by about 1.9 and 1.4 W m⁻².

Global distribution of aerosol direct radiative forcing in the ultraviolet and visible arising under clear skies

A deterministic atmospheric spectral radiative transfer model, that uses comprehensive climatological data, is developed to compute the global distribution of mean monthly clear-sky total direct aerosol radiative forcing in the ultraviolet (UV) and visible, between 0.2–0.85 μm, at the top of the atmosphere (TOA), within the atmosphere and at the Earth’s surface for winter and summer conditions. The aerosol data were taken from the Global Aerosol Data Set (GADS), given for various fixed relative humidity values and for 11 wavelengths within the UV—visible range, both for natural and anthropogenic aerosols. We first derive global climatologies of extinction aerosol optical thickness (AOT), single-scattering albedo (ωaer) and asymmetry factor (gaer), for actual relative humidity values within the aerosol layer, based on the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR) Reanalysis Project and the Tiros Operational Vertical Sounder (TOVS) datasets. We include the global distribution of cloud cover using the D2 data from the International Satellite Cloud Climatology Project (ISCCP), to define the clear-sky fraction at the pixel level for each month. Supplementary 10-yr climatological data for surface and atmospheric parameters were taken from NCEP/NCAR, ISCCP-D2 and TOVS. Our present analysis allows the aerosol radiative properties and forcings to vary with space, time and wavelength. The computed mean annual global AOT, ωaer and gaer values are found to be 0.08, 0.96 and 0.73, respectively, at 0.5 μm. On a mean monthly 2.5¼ pixel resolution, aerosols are found to decrease significantly the downward and the absorbed solar radiation at the surface, by up to 28 and 23 W m−2, respectively, producing a surface cooling at all latitudes in both winter and summer. Aerosols are found to generally increase the outgoing solar radiation at TOA (planetary cooling) while they increase the solar atmospheric absorption (atmospheric warming). However, the model results indicate that significant planetary warming, by up to 5 W m−2, can occur regionally, such as over desert areas, due to strong aerosol absorption. A smaller planetary warming (by up to 2 W m−2) is also found over highly reflecting ice- or snow-covered areas, such as Antarctica and Greenland, as well as over Eastern Europe, Siberia and North America. In general, the aerosol-induced surface cooling exceeds the induced atmospheric warming, except for regions characterized by strong aerosol absorption (e.g. deserts). On a mean annual global basis, natural plus anthropogenic aerosols are found to cool the Earth by 0.6 W m−2 (they increase the planetary albedo by 0.28%), to heat the atmosphere by 0.8 W m−2, while they decrease the downward and net surface solar radiation (surface cooling) by about 1.9 and 1.4 W m−2.

Generating Rainfall and Temperature Scenarios at Multiple Sites: Examples from the Mediterranean

A statistical downscaling methodology was implemented to generate daily time series of temperature and rainfall for point locations within a catchment, based on the output from general circulation models. The rainfall scenarios were constructed by a two-stage process. First, for a single station, a conditional first-order Markov chain was used to generate wet and dry day successions. Then, the multisite scenarios were constructed by sampling from a benchmark file containing a daily time series of multiple-site observations, classified by season, circulation weather type, and whether the day is wet or dry at the reference station. The temperature scenarios were constructed using deterministic transfer functions initialized by free atmosphere variables. The relationship between the temperature and rainfall scenarios is established in two ways. First, sea level pressure fields define the circulation weather types underpinning the rainfall scenarios and are used to construct predictor variables in the temperature scenarios. Second, separate temperature transfer functions are developed for wet and dry days. The methods were evaluated in two Mediterranean catchments. The rainfall scenarios were always too dry, despite the application of Monte Carlo techniques in an attempt to overcome the problem. The temperature scenarios were generally too cool. The scenarios were used to explore the occurrence of extreme events, and the changes predicted in response to climate change, taking the example of temperature. The nonlinear relationship between changes in the mean and changes at the extremes was clearly demonstrated.

Polar Cloud Climatologies from ISCCP C2 and D2 Datasets

Abstract A deterministic radiative transfer model along with data from the International Satellite Cloud Climatology Project (ISCCP) and the Earth Radiation Budget Experiment (ERBE) were used to examine long-term mean monthly cloud climatologies for the polar regions, as given by the ISCCP C2 and D2 datasets. Significant improvement was found in the new reprocessed D2 data in terms of comparison of model fluxes with ERBE longwave radiant exitances (LWREs) at the top-of-atmosphere (TOA) over Antarctica. This improvement results from slightly higher surface temperature values, and from larger high-level cloud amounts in the D2 than in the C2 dataset. In general, D2 gives larger cloud cover, Ac, than C2, more in the southern than in the northern polar regions, mostly attributed to high-level clouds missed by ISCCP C2. The Ac differences between C2 and D2 increase toward the South Pole and, according to the D2 data, the Arctic has only about 10% high-level cloud cover compared with 45% in Antarctica, during t...

Discrete Particle Distribution Model for Advection-Diffusion Transport

A new methodology, named DisPar, based on a discrete probability distribution for a particle displacement, was developed to solve 1D advection-diffusion transport problems in water bodies. The discrete probability distribution for the particle displacement was developed as an average and variance function. These probabilities were used to predict the deterministic mass transfer between cells in one time step, and therefore the particle concentration in each cell was considered the state variable. The state equation was found to be similar to an explicit finite-difference formulation with a Eulerian grid. The model stability, positivity, and mass conservation are guaranteed by the probability distribution concept. DisPar produces solutions without numerical dispersion for constant velocity, diffusion coefficient, and cross-sectional area. In these conditions, DisPar was also developed as a function of space and time for an instantaneous mass spill. When the stability and positivity restrictions were respected, the model produced excellent results when compared to analytical solutions and other methods. The discrete particle displacement distribution concept differs from other numerical formulations, and therefore it represents a new modeling technique.

Systematic approach to the digital compensation for deterministic nonideal characteristics in ΣΔ modulation

In this work we propose a systematic approach to the digital compensation for nonideal deterministic characteristics in a /spl Sigma//spl Delta/ modulator. It is based on inverting the complete nonlinear deterministic transfer function of the modulator. This operation leads us to a whole set of possible reconstruction estimates from which we systematically pick the geometric center as signal decoding scheme. This approach already proves effective in the particular case of static deviations in the built-in analog-to-digital converter and digital-to-analog converter of the modulator.

Le rayon spectral essentiel de l'opérateur de Ruelle sur des variétés höldériennes

We study the deterministic and random Ruelle transfer operator L induced by an expanding map ƒ of a smooth n-dimensional manifold X and a bundle automorphism ϑ of a rank L vector bundle E. We prove the following exact formula for the essential spectral radius of L on the space C r, α of r-times continuously differentiable sections of E with α-H o ̈ lder r-th derivative: r ess( L;C r,α) = exp ( vϵrg sup {h v + λ v, − (r+α)x v}) , where Erg denotes the set of ƒ-ergodic measures, h v the entropy of ƒ with respect to v, λ v the largest Lyapunov exponent of the cocycle ϑ (x) = ϑ(ƒ k−1(x) ·…· ϑ(x) , and x v the smallest Lyapunov exponent of the differential Dƒ k(x) , x ϵ X, k = 1, 2,…. A similar result holds for the random case.