1. Nižetić, S. (2010): An atmospheric gravitational vortex as a flow object: improvement of the three-layer model. Geofizika, 27, 1-20.
ABSTRACT:
An improved physical and analytical three-layer model of gravitational vortex columns (GVCs) for solar chimney power plants is developed in this paper. In essence, this model represents a further improvement and upgrade of the three-layer model proposed in Ninić et al. (2009). The improvements of the three-layer model deal with internal friction, variable vertical velocity (by height) in the central GVC spiraling upward flow, and variable angular momentum of the downdraft shell. A numerical solution of the improved model is given as a characteristic case and is compared to the elementary GVC model. The results show that the introduced improvements are important parameters for further analysis of gravitational vortex columns.
Keywords: Gravitational vortex, solar chimney, numerical modelling.
2. Doklestić, D., Fuchs, Ž. and Marki, A. (2010): Convectively coupled Kelvin waves and convective inhibition. Geofizika, 27, 21-36.
ABSTRACT:
We use a thermodynamic assumption that the vertical heating profile has the shape of the first baroclinic mode, and that the analytical expression for vertical velocity has two modes, representing shallow and deep convection. The thermal assumption of the model is given through the convective inhibition closure, i.e. negative convective inhibition results in increased precipitation. These modeled modes are the free Kelvin waves and the convectively coupled Kelvin waves. We find the latter mode to be unstable, with maximum growth rate at wavelengths of 6 000 kilometers. The model successfully captures the observed nature of the Kelvin waves and shows that convective inhibition closure is sufficient to trigger the observed destabilization of the convectively coupled Kelvin mode.
Keywords: Large-scale modes, tropics, destabilization.
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3. Chen, X. and Li, B.-L. (2010): Global scale assessment of the relative contribution of climate and non-climate factors on annual vegetation change. Geofizika, 27, 37-43.
ABSTRACT:
The impact and its change on the Earth’s biosphere from climate and non-climate factors are of grave concern due to increasing human activities. In this study we used a systematic method to assess the relative importance of climate and non-climate factors on annual global and continental vegetation dynamics based on global NDVI at 1-km resolution and surface climate data from main stations of the World Meteorological Organization between April 1998 and December 2002. The indices of relative importance of climate and non-climate fluctuations on vegetation dynamics at each continent before and after July 2000 (two equal time periods) were also compared. Our results indicated that the vegetation dynamics on a continental and global scale during this short time period was dominated by climate fluctuations, however, the relative importance of climate and non-climate factors on yearly vegetation dynamics differed among continents. Despite the dominant role of climate on vegetation dynamics during these two time periods for all continents, the relative importance of climate on vegetation dynamics increased slightly in south-east Asia, North America, Africa, Australia and New Zealand, but decreased slightly in South America, Central America, west Asia, north Asia, Europe and globally. This method may be helpful in monitoring the impacts from climate and non-climate factors on global vegetation dynamics.
Keywords: Continents, global vegetation dynamics, NDVI, relative importance of climate and non-climate factors
4. Narayan, J. P. and Kumar, S. (2010): A 4th order accurate P-SV wave staggered grid finite difference algorithm with variable grid size and VGR-stress imaging technique. Geofizika, 27, 45-68.
ABSTRACT:
The implementation of VGR-stress imaging technique, as a free surface boundary condition, in a (2, 4) staggered grid P-SV wave finite difference (FD) algorithm with a variable size of a grid cell is presented in this paper. VGR is acronym for 'vertical grid-size reduction'. The qualitative and quantitative results confirmed that the effective thickness (ETH) of the first soil layer become less by one-half of the vertical size of a grid cell than the assigned thickness (ATH), if stress imaging technique is used as a free surface boundary condition. The results of various numerical experiments revealed that the stress imaging technique causes significant numerical dispersion of Rayleigh waves and the VGR-stress imaging technique is efficient enough to avoid the same. So, superiority associated with the VGR-stress imaging technique over the well stress imaging technique is that it avoids both the significant numerical dispersion of Rayleigh waves in homogeneous medium and the soil thickness discrepancy. The maximum grid spacing ratio (ratio of largest to smallest size of a grid cell) up to 6.0 did not affect the accuracy of FD algorithm with a variable size of a grid cell. In case of a variable size of a grid cell, the required computational memory and time for a particular basin-edge model was 6.43 and 16.62 times lesser than that required in case of uniform grid.
Keywords: P-SV wave finite difference algorithm, fourth order spatial accuracy, maximum grid spacing ratio, VGR-stress imaging technique, stability and grid dispersion
Varia
5. Lisac, I. (2010): Approaching the 300th anniversary of the birth of Josip Ruđer Bošković. Geofizika, 27, 69-78.
ABSTRACT:
On the occasion of 300th anniversary of the birth of Josip Ruđer Bošković, a Jesuit, versatile scientist, philosopher, diplomat and poet – originally from Dubrovnik, who worked in the 18th century – this paper presents a contribution of his importance. This is a review of one of his first papers which has recently been translated from Latin into Croatian and which explains the appearance of northern lights. Bošković was the first Croatian scientist who dealt with the explanation of this atmospheric phenomenon, and some of his conclusions are close to modern ideas. This paper also presents a recently discovered memorial poem which his younger fellow brother p. Petar Perica wrote on the occasion of the 200th anniversary of Bošković’s birth and which was hitherto unknown.
Keywords: J. R. Bošković, J. R. Boscovich, northern lights, aurora, memorial poem by p. Petar Perica