Grid computing for atmospheric composition studies in Bulgaria

Three Grid applications from the SEE-GRID-SCI Environmental VO are developed by the Bulgarian project team: Climate Change Impact on Air Quality (CCIAQ); Multi-scale atmospheric composition modeling (MSACM); Modeling System for Emergency Response to the Release of Harmful Substances in the Atmosphere (MSERRHSA). The three applications concern problems of significant socio-economic significance. They are all dedicated to air pollution studies, but address different goals and so face different problems and requirements. The applications are briefly presented in the paper. Examples of the different applications validations are given. Some application results are shown and commented.     

On the dynamics and effects of double-diffusively driven intrusions

Some of the characteristics of intrusive finestructure observed in oceanic fronts suggest that salt fingering is active in the intrusions. An extension of Stern's 1967 study of the stability of a thermohaline front to intrusive finestructure driven by salt fingers is presented to investigate this hypothesis. Intrusions are found to grow due to the salt finger induced density fluxes even in the presence of small scale momentum dissipation. The presence of this dissipation defines a fastest growing mode for the disturbance which has physical characteristics not unlike those observed in oceanic fronts. The model results do not agree well with the laboratory studies of intrusions. For many fronts, the model requires initial perturbations in the front which can support salt fingers. Linear internal waves are investigated to determine if they can provide the initial perturbation. It is shown that, away from the equator, the interaction between internal waves and intrusions is weak because of a mismatch of time scales. Finally, growing intrusions are shown to flux heat, salt and density across fronts. The senses of these fluxes are to run down the lateral gradients of many oceanic fronts.     

Satellite de-orbiting via controlled solar radiation pressure

We analyze the families of central configurations of the spatial 5-body problem with four masses equal to 1 when the fifth mass m varies from 0 to \(+\infty \). In particular we continue numerically, taking m as a parameter, the central configurations (which all are symmetric) of the restricted spatial (\(4+1\))-body problem with four equal masses and \(m=0\) to the spatial 5-body problem with equal masses (i.e. \(m=1\)), and viceversa we continue the symmetric central configurations of the spatial 5-body problem with five equal masses to the restricted (\(4+1\))-body problem with four equal masses. Additionally we continue numerically the symmetric central configurations of the spatial 5-body problem with four equal masses starting with \(m=1\) and ending in \(m=+\infty \), improving the results of Alvarez-Ramírez et al. (Discrete Contin Dyn Syst Ser S 1: 505–518, 2008). We find four bifurcation values of m where the number of central configuration changes. We note that the central configurations of all continued families varying m from 0 to \(+\infty \) are symmetric.     

On the nature of bright rims of filaments

A filament with a very bright rim was observed in the H line on May 11, 1989, using the Meudon spectroheliograph. Absolute calibration of the spectroheliogram allows us to express the intensities in particular sites of the filament, in its bright rim and inside the surrounding chromosphere. From a large number of photometric scans, we obtained a histogram of the intensity excess of the bright rim relative to the quiet chromosphere. The mean value of this excess amounts to about 4%. We present a theoretical explanation of bright rims, based on the nature of H radiative diffusion in the filaments. Computed NLTE model of the filament leads to a rim intensity excess which is in good agreement with our observations.     

Problems of simulation of large,long-lived vortices in the atmospheres of the giant planets (jupiter,saturn, neptune)

Large, long-lived vortices are abundant in the atmospheres of the giant planets. Some of them survive a few orders of magnitude longer than the dispersive linear Rossby wave packets, e.g. the Great Red Spot (GRS), Little Red Spot (LRS) and White Ovals (WO) of Jupiter, Big Bertha, Brown Spot and Anne's Spot of Saturn, the Great Dark Spot (GDS) of Neptune, etc. Nonlinear effects which prevent their dispersion spreading are the main subject of our consideration. Particular emphasis is placed on determining the dynamical processes which may explain the remarkable properties of observed vortices such as anticyclonic rotation in preference to cyclonic one and the uniqueness of the GRS, the largest coherent vortex, along the perimeter of Jupiter at corresponding latitude.We review recent experimental and theoretical studies of steadily translating solitary Rossby vortices (anticyclones) in a rotating shallow fluid. Two-dimensional monopolar solitary vortices trap fluid which is transported westward. These dualistic structures appear to be vortices, on the one hand, and solitary waves, on the other hand. Owing to the presence of the trapped fluid, such solitary structures collide inelastically and have a memory of the initial disturbance which is responsible for the formation of the structure. As a consequence, they have no definite relationship between the amplitude and characteristic size. Their vortical properties are connected with geostrophic advection of local vorticity. Their solitary properties (nonspreading and stationary translation) are due to a balance between Rossby wave dispersion and nonlinear effects which allow the anticyclones, with an elevation of a free surface, to propagate faster than the linear waves, without a resonance with linear waves, i.e. without wave radiation. On the other hand, cyclones, with a depression of a free surface, are dispersive and nonstationary features. This asymmetry in dispersion-nonlinear properties of cyclones and anticyclones is thought to be one of the essential reasons for the observed predominance of anticyclones among the long-lived vortices in the atmospheres of the giant planets and also among the intrathermocline oceanic eddies.The effects of shear flows and differences between the properties of monopolar vortices in planetary flows and various laboratory experiments are discussed. General geostrophic (GG) theory of Rossby vortices is presented. It differs essentially from the traditional quasi-geostrophic (QG) and intermediate-geostrophic (IG) approximations by the account of (i) all scales between the deformation radius and the planetary scale and (ii) the arbitrary amplitudes of vortices. It is shown that, unlike QG- and IG-models, the GG-model allows for explaining the mentioned cyclonic-anticyclonic asymmetry not only in planetary flows, but also in laboratory modeling with vessels of near paraboloidal form.     

On the narrowing of the ionospheric absorption anomaly by solar eclipses

Summary One of the most interesting effects in theD-region by solar eclipses is the narrowing of the absorption anomaly on observing the long and middle waves. The theoretical analysis carried out by means of the continuity equation shows that the observed effects are due to the versatile behaviour of the equation terms and most of all to the ratios of the negative ions to electrons . In the course of the eclipse, increases which has as a consequence a whole series of quantitative and qualitative variations in the absorbing plasma of theD-region. The frequency dependence of the narrowing effect is due to the different height of reflection of the long (0.1Mc/s) and middle (1 Mc/s) waves. The link of the magnitude of the anomaly with the solar zenith angle is a result of the complex mutual dependency between the change velocity of the electrons and negative ions as well as of the opposite or simultaneous change of the solar zenith angle and the visibility of the solar disc. The near coincidence of the theory with experiment confirms the validity of the initial equations for the ratios of the negative ions to electrons, for the coefficient of dissociative recombination and for the lower boundary of theD-region. The idea of the immediate recovering of quasi-equilibrium for negative ions after sunrise is not real. In the course of an eclipse quasi-equilibrium is lacking both for negative ions and electrons.

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Zusammenfassung Die auffälligste Erscheinung in derD-Region bei den Sonnenfinsternis-beobachtungen im Lang- und Mittelwellenbereich ist der Einengungseffekt der Absorptionsanomalie. Die durchgeführte theoretische Analyse auf Grund der Bilanzgleichung zeigt, daß der Einengungs-effekt eine Folge des verschiedenartigen Verhaltens der Glieder in der Rekombinationsgleichung ist. Im Laufe der Sonnenfinsternis wächst der Attachmentparameter an, was eine Reihe von qualitativen und quantitativen Veränderungen des absorbierenden Plasmas in derD-Region verurschacht.-Die Frequenzabhängigkeit der zeitlichen Einengung der Sonnenfinsterniseffekte beruht auf der verschiedenen Reflexionshöhe der Lang-und Mittelwellen. Die Abhängigkeit des Einengungseffekts von der Tagesstunde ist eine Folge der wechselseitigen Abhängigkeit zwischen Bildungsgeschwindigkeit von Elektronen und negativen Ionen, sowie der ein-oder gegensinnigen Änderung der Belichtung der Sonnenscheibe und des Zenitwinkels der Sonne.-Die gute Übereinstimmung zwischen Theorie und Experiment bestätigt die Richtigkeit der Eingangsgleichungen für die negativen Ionen, für die dissoziativen Rekombinationskoeffizient und für die untere Grenze derD-Region.-Die Auffassung von der unmittelbaren Herstellung des Gleichgewichts zwischen negativen Ionen und Elektronen in derD-Region gleich nach dem Sonnenaufgang ist nicht berechtigt. Im Laufe der Sonnenfinsternis sind keine Gleichgewichtsbedingungen vorhanden.

     

Reduktion der Strahlungsmessungen auf mittlere Sonnen-Entfernung

Summary Supplying the resp. remark ofK. Wegener (this Review: XVI, 1950, p. 16) the different cases have been fixed, when the measured intensities of solar radiation should be reduced according to the mean solar distance, or when not. An international recommendation for the details of evaluation and publication on solar radiation seems desirable.     

Temperature calibration of expendable bathythermographs

A non-destructive temperature calibration system for expendable bathythermographs (XBT) is described. A transfer standard technique has been used to estimate XBT thermistor probe-to-probe temperature variability. One-point calibration results suggest that a standard deviation of 0.025°C is typical at 10°C. Additional calibration data from nine XBT thermistors suggest that probe-to-probe temperature variability is largest at 0°C (ca. 0.03°C) and decreases uniformly to a minimum at 30°C (ca. 0.01°C).