Satne vrijednosti dozračene Sunčeve energije pri uvjetima vedrog neba

Hourly values of global solar irradiation in clear skies are determined as a function of solar elevation using empirical parameters derived from the measurements of radiation in Zagreb (f = 45.828° N, l= 15.992° E) in the period between 1960 and 1985. The estimation was performed on the 15th of every month for geographical latitudes between 41° and 46° N. By means of the well known procedure the global solar radiation is then divided into the direct and diffuse solar radiation and calculated for a south-facing surface inclined at 35°. A possibility of taking into consideration the influence of clouded sky on the decrease in the clear-sky solar irradiation is also presented

Adaptations of succulent plants for survival in desert ecosystems

Cilj ovog seminara bio je nabrojati prilagodbe sukulentnih biljaka koje su im nužne za preživljavanje u pustinjskim ekosustavima. Sukulenti su biljke koje imaju posebne morfološke i ekofiziološke prilagodbe za pojačano primanje i pohranu vode. Razlog zašto bez takvih prilagodbi ne bi mogle preživjeti je što žive u pustinjama i polupustinjama, aridnim područjima u kojima je voda glavni ograničavajući čimbenik. Kiša pada rijetko i uglavnom nepredvidljivo, tlo ne može primiti puno vode pa ju biljke moraju u najkraćem mogućem vremenu skupiti u što većim količinama. Neke biljke sušno razdoblje preživljavaju u obliku sjemenki, neke ispod zemlje, a neke opstaju u punoj veličini i prkose suši. Sukulenti koriste CAM fotosintezu, da bi puči mogli držati otvorene samo po noći i tako smanjiti transpiraciju. Moraju imati posebna tkiva za spremanje vode, a stanice hidrenhima moraju imati elastične stijenke kako bi mogle podnositi velike razlike u volumenu vode bez velike promjene u turgoru. Razgranat i plitak korijenski sustav pomaže u primanju vode za vrijeme kiše. Kloroplasti se od prejake radijacije, koja bi mogla izazvati fotoinhibiciju, štite skupljanjem u nakupine. Sve ove, i mnoge druge prilagodbe, čine sukulente izuzetno zanimljivom skupinom biljaka.The goal of this seminar was to list the adaptations of succulent plants that are necessary for their survival in desert ecosystems. Succulents are plants that have special morphological and ecophysiological adaptations for increased water uptake and storage. The reason why they could not survive without such adaptations is that they live in deserts and semi-deserts, arid environments in which water is the main limiting factor. Precipitation is rare and occurs randomly, the soil cannot uptake a lot of water, so the plants have to collect as much as possible of it in the shortest possible amount of time. Some plants survive the dry period in the form of seeds, some survive mostly under the ground, while others persist above ground in their full form and defy the drought. Succulents use CAM photosynthesis in order to be able to minimize transpiration by only keeping the stomata open at night. They have special water-storage tissues, and the hydrenchyma cells need to have high elasticity cell walls in order to withstand big differences in water volume, without a significant turgor change. The ramified and shallow root system helps uptake water during rain. Chloroplasts protect themselves from too high radiation, that could cause photoinhibition, by clustering together. All of the above, as well as many other adaptations, make succulents an extremely interesting group of plants

On the spring sunshine regime in Croatia

The irregular increase of cloudiness in Croatia in spring was found and briefly explained by J. Goldberg. This paper analyses the distribution functions of daily relative sunshine duration at 14 meteorological stations and the mean mounthly cloudiness at 131 stations in a recent climate. It is shown that the part of Croatia affected by the sunshine regime decline is not the same at the beginning and at the end of spring. The increase of cloudiness in March and April is mostly produced by the Mediterranean lows on the Adriatic or passing over continental Croatia. The diminished or non-existing decrease of cloudiness in June is due to the atmospheric disturbances from Atlantic, passing over central Europe. In both cases the windward sides of mountains are especially affected

Osvrt na meteorološka istraživanja u Hrvatskoj do 1997.

This review of meteorological research is based on the published professional and scientific papers. Papers are divided into 19 main topics: books, measurements and data processing, solar energy, planetary boundary layer, ecological problems, climatological papers, research on wind and air humidity, traffic and agricultural meteorology, hail defense, biometeorology, air- sea interaction, atmospheric electricity, history of meteorology, research projects and other activities. For every group, main research problems and achieved results are outlined on the basis of selected papers, which are quoted in the list of references. This list does not include complete bibliography of meteorological papers published so far in Croatia. However, it was in- tended to include all authors with some of their papers in order to get insight into research they were involved with, and their contribution. The first meteorological papers commenced to appear in the middle of the nineteenth century but the greatest number of papers has been published in the last 50 years. This is in harmony with the development of meteorology as profession and of meteorological institutions: Geophysical Institute "Andrija Mohorovičić" and Meteorological and Hydrological Service.Pregled meteoroloških istraživanja izrađen je na osnovi objavljenih znanstvenih i stručnih radova. Tematski su radovi svrstani u 19 skupina: knjige, mjerenja i obrada podataka, sunčana energija, numeričko modeliranje, analiza i prognoza vremena, planetarni granični sloj, ekološka problematika, klimatološki radovi, istraživanje vjetra i vlage u zraku, prometna i poljoprivredna meteorologija, obrana od tuče, biometeorologija, međusobno djelovanje atmosfere i mora, atmosferski elektricitet, povijest meteorologije, istraživački projekti i ostale djelatnosti. Unutar svake skupine navode se glavni problemi istraživanja i postignuti rezultati na osnovi odabranih radova, koji se navode u popisu literature. Taj popis dakle ne sadrži cjelokupnu bibliografiju meteoroloških radova dosad objavljenih u Hrvatskoj. Ipak se nastojalo obuhvatiti sve autore s nekoliko njihovih djela, da se dobije uvid čime su se pojedinci bavili i koji je njihov doprinos. Vidljivo je da su prvi meteorološki radovi na hrvatskom počeli izlaziti sredinom 19. st., a najveći broj radova da je objavljen u posljednjih 50 godina. To se poklapa s razvojem struke i meteoroloških institucija: Geofizičkog zavoda Andrija Mohorovičić i Državnog hidrometeorološkog zavoda

Collective excitations in open-shell metal clusters: The time-dependent local-density approximation applied to the self-consistent spheroidal jellium particle

The self-consistent and microscopic time-dependent local-density-approximation (TDLDA) formalism for the calculation of the dynamical electronic response properties of open-shell, axially deformed small metal clusters is presented in detail. The model is based on the self-consistent ground-state calculation of the spheroidal jellium model, giving the optimized cluster shape, driven by its open-valence-shell electronic structure. First results on the static and dynamical electronic polarizability of the strongly axially deformed Na10 cluster are reported and compared with the experimental polarizability and photoabsorption cross-section results. The variety of the future applications of the model is outlined, as well as the possible improvement of the formalism

About Modelling of Complex Networks with Applications to Terrorist Group Modelling

Based on available data on various organisations and networks, the article explores some key properties of the structure of a terrorist organisation. Analytical focus is on lower levels of organisational hierarchy, where network structure with exponential distribution of the number of links among network nodes is clearly visible. Such networks tend to grow organically, are very efficient in information diffusion, and are robust regarding stochastic failures and targeted attacks. These network features are illustrated by recent example based on network data about September 11, 2001 attacks on New York and Washington

BILJEŠKE IZ 17. I 18. STOLJEĆA O VREMENU U MAKARSKOJ

Bilješke o vremenu iz ljetopisa franjevačkog samostana u Makarskoj razmatraju se s obzirom na sadržaj i nazivlje. Na temelju zapisa fra Nikole Gojaka koji je vodio kroniku 60 godina provedena je osnovna kiimatološka analiza godišnjeg hoda i trajanja nekih vremenskih tipova u Makarskoj

Global radiation in Yugoslavia for a Rayleigh atmosphere model

The paper deals with ground values of incoming Solar energy in the 41° – 47°N zone and in the 0 – 3000 metre altitude range, on the assumption of Rayleigh atmosphere model. The analysis is based on daily global radiation. A comparison with measured data shows that daily radiation for Rayleigh atmosphere model as a rule exceed that of real daily radiation near the ground, especially at little altitudes. The radiation for a Rayleigh model can be exceeded only rarely, in the case of relatively clear and dry air and strong reflection on suitable situated clouds or on fresh snow. Rayleigh atmosphere over Yugoslavia transmits 82 – 93% energy to the ground. In spite of great transmissibility, this model still influences the position of moving radiation maximum in summer, reaching 43°34’N at the upper level of the atmosphere, and not above 41°N at the sea level. The essential difference between the territorial distribution of global radiation over Yugoslavia for Rayleigh atmosphere and the known distributions derived from sunshine duration and from cloudiness is in the fact that radiation isolines in the model mostly follow the parallels of latitude, and radiation isolines for a real atmosphere follow the direction of the coastline, i.e. the highest mountain ranges. The other essential difference is in the mountains. The higher the mountains, the greater the energy coming through dry clean atmosphere. Due to orographic cloudiness, global radiation in real atmosphere is less intensive in the mountain areas of Yugoslavia than over the Adriatic basin and the Pannonian plain

Riječ oborina i njezino značenje u meteorologiji

lstraženo je kada se u hrvatskim rječnicima pojavila imenica oborina i od kada se upotrebljava kao meteorološki naziv. Objašnjeno je zašto je u meteorologiji prihvaćen taj naziv, a ne neki nastao od glagola padati. Kronološki se navode definicije oborine u hrvatskih meteorologa i primjeri definicija odgovarajućih stručnih naziva u nekim drugim jezicima