Lunisolar Apsidal Resonances at low Satellite Orbits

Eccentricity resonances between the secular motion of an Earth satellite's orbit and the longitudes of the Sun and the Moon are studied within a Hamiltonian framework. The problem is approximated in a traditional manner, with the Earth's potential including only the second zonal harmonic, and a Hill‐type approximation for perturbing bodies. For a family of 10 resonances, stable and unstable points are identified and libration widths are estimated. Numerical values are given for the maximum variation of eccentricity available at each resonance. The respective amplitudes of the perigee heights' librations range from 2 to 750 km. The resonances of the solar origin are generally stronger than their lunar counterparts. This revised version was published online in July 2006 with corrections to the Cover Date.     

Extended Fundamental Model of Resonance

Fundamental models are the simplest, one degree of freedom Hamiltonians that serve as a tool to understand the qualitative effects of various resonances. A new, extended fundamental model (EFM) is proposed in order to improve the classical, Andoyer type, second fundamental model (SFM). The EFM Hamiltonian differs from the SFM by the addition of a term with the third power of momentum; it depends on two free parameters. The new model is studied for the case of a first-order resonance, where up to five critical points can be present. Similarly, to the respective SFM, it admits only the saddle-node bifurcations of critical points, but its advantage lies in the capability of generating the separatrix bifurcations, known also as saddle connections. The reduction of parameters for the EFM has been performed in a way that allows the use of the model in the case of the so-called abnormal resonance.     

Early stage of critical clusters growth in phenomenological and molecular dynamics simulation models

The growth of critical clusters is discussed in the paper according to the classical and molecular dynamics (MD) approaches. A new formula for molecule numbers in critical clusters has been derived within the framework of the classical approach. A set of equations controlling the early stage of growth in a neighborhood of a critical size is presented. As far as molecular dynamics simulation is concerned, a computational technique based on the DL_POLY code is described in brief. Computation results are presented concerning cluster formation of H₂O vapor, distribution of clusters versus time, cluster growth and radial density distribution of isolated clusters. A comparison with the classical results is made for a case of dense vapor, where the mechanism of strong condensation is predominant. The Hertz–Knudsen formula seems to be verified by the molecular dynamics results.     

Temporal variations in heat fluxes over a central European city centre

Summary Energy fluxes have been measured over an area near the centre of the city of Łódź, Poland, since November 2000. The site was selected because the building style (surface cover and morphology) is typical of European cities, yet distinct from the majority of cities where energy balance observations have been studied thus far. The multi-year dataset permits consideration of temporal changes in energy balance partitioning over a wide range of seasonal and synoptic conditions and of the role of heat storage and anthropogenic fluxes in the energy balance. Partitioning of net radiation into the turbulent fluxes is consistent in the two years, with the largest differences occurring due to differing precipitation. The monthly ensemble diurnal cycles of the turbulent fluxes over the two years are similar. The largest differences occur during the July–September period, and are attributable to greater net radiation and lower rainfall in 2002. The latent heat flux accounts for approximately 40% of the turbulent heat transfer on an annual basis. The average daily daytime Bowen ratio and its variability are slightly reduced during the summer (growing) season. Anthropogenic heat is a significant input to the urban energy balance in the winter. The fluxes observed in this study are consistent with results from other urban sites.     

Tourist farms in Lower Silesia, Poland

In view of the small size of most Polish farms, attempts have been made to encourage diversification into rural tourism. The paper examines the progress made in Lower Silesia which has good resources for domestic and international tourism. Thanks to the promotional work of the Agricultural Consultative Centres over a hundred farms are now providing services. They do not generate a large share of the farm income but business is expanding and some areas are becoming very popular. Thus a base has been established for future expansion. Further development depends on easier access to credit and government support for ecological agriculture. Better promotion is also needed to increase interest in rural tourism in Poland and attract more visitors from abroad. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nondimensionalization of the Atmospheric Boundary-Layer System: Obukhov Length and Monin–Obukhov Similarity Theory

Boundary-Layer Meteorology - The Obukhov length, although often adopted as a characteristic scale of the atmospheric boundary layer, has been introduced purely based on a dimensional argument...     

Completely Integrable Systems Connected with Lie Algebras

In a recent paper Ballersteros and Ragnisco (1998) have proposed a new method of constructing integrable Hamiltonian systems. A new class of integrable systems may be devised using the following sequence: , where A is a Lie algebra is a Lie–Poisson structure on R ₃, C is a Casimir for is a reduced Poisson bracket and (A, ▵) is a bialgebra. We study the relation between a Lie-Poisson stucture Λ and a reduced Poisson bracket , which is a key element in using the Lie algebra A to constructing this sequence. New examples of Lie algebras and their related integrable Hamiltonian systems are given. This revised version was published online in July 2006 with corrections to the Cover Date.