Utjecaj perioda osrednjavanja meteoroloških parametara na procjenu stabilnosti prizemnog sloja atmosfere

Uobičajeni parametar za određivanje standardnih devijacija vertikalnog (σz) i lateralnog (σy) rasapa primjesa ispuštenih u atmosferu je satna procjena stabilnosti prizemnog sloja atmosfere. Metodu za takvo određivanje čine Pasquill-Giffordove krivulje. Prelaz na kraće periodičke srednjake stabilnosti (desetminutne, dvadesetminutne i tridesetminutne) pokazuje postojanje razlika i do tri klase u odnosu na satni srednjak stabilnosti. Sve navedene razlike ukazuju da je potrebno koristiti desetminutne srednjake stabilnosti u određivanju σz i σy

Returning to work after suffering from burnout syndrome: Perceived changes in personality, views, values, and behaviors connected with work

To date only a few studies have focused on returning to work after suffering from burnout syndrome. Participants were asked about their perceived work effectiveness, changes in their personal values, and obstacles and support factors that they encountered when they returned to work. Among the 27 individuals of various professions included in the study, 18 achieved an average or a high score on the Maslach Burnout Inventory, which was used to conduct a semi-structured interview. The answers were later processed by analyzing the content. The results showed that burned-out individuals only slowly return to work after recovery. When they return to work, they encounter changes in personality, personal values, and work effectiveness, and they only receive partial support from the environment. The results draw attention to insufficient detection of the disease by medical staff and employers in Slovenia. Recovering from burnout is a long-term process, which depends most on individuals themselves. At the same time, they can receive the necessary support from their family and coworkers, especially in terms of understanding them and partially adapting their responsibilities at work when they return. This study draws attention to a number of factors that can influence an individual’s process of returning to work and can be used as a basis for developing systematic rehabilitation programs

Regionalna analiza obrazaca brzine vjetra u složenom terenu

Wind energy is a weather and climate-dependent energy resource with natural spatio-temporal variabilities at time scales ranging from fraction of seconds to seasons and years, while at spatial scales it is strongly affected by the terrain and vegetation. To optimize wind energy systems and maximize the energy extraction, wind measurements on various time scales as well as wind energy forecasts are required and needed. This study focuses on spatio-temporal characteristics of the wind velocity in complex terrain, relevant to wind energy assessment, operation, and grid integration, using data collected at 11 towers ranging from 40 to 80 m tall over a 12-year period in complex terrain of western-central and northern Nevada, USA. The autocorrelation analysis, Detrended Fluctuation Analysis (DFA) and Detrended Cross-Correlation Analysis (DCCA) showed strong coherence between the wind speed and direction with slowly decreasing amplitude of the multi-day periodicity with increasing lag periods. Besides pronounced diurnal periodicity at all locations, statistical analysis and DFA also showed significant seasonal and annual periodicities, long-memory persistence with similar characteristics at all sites and towers with a relatively narrow range of the Weibull parameters. The DCCA indicates similar wind patterns at each tower, and strong correlations between measurement sites in spite of separations of about 300 km across the towers’ setup. The northern Nevada area exhibits higher wind resource potential and higher wind persis-tence compared to the western-central region. Overall, the DFA and DCCA results suggest higher degree of complementarity among wind data at measure-ment sites compared to previous standard statistical analysis.Energija vjetra je energetski resurs ovisan o vremenu i klimi s prirodnim prostorno-vremenskim promjenjivostima koje u vremenskim razmjerima idu od sekundi do sezona i godina, dok su na prostornim razmjerima promjenjivosti snažno uvjetovane složenošću terena i vegetacije. Kako bi se optimizirali sustavi energije vjetra i maksimizirala ekstrak-cija energije, potrebna su mjerenja vjetra u različitim vremenskim razmacima, kao i prognoze energije vjetra. Ova studija se fokusira na prostorno-vremenske karakteristike brzine vjetra u složenom terenu, relevantne za procjenu energije vjetra i integraciju u elektrodistribucijske mreže, koristeći podatke prikupljene na 11 tornjeva s rasponima visina od 40 do 80 m tijekom 12-godišnjeg razdoblja u složenoj topografiji zapadno-središnje i sjeverne Nevade, SAD. Autokorelacijska analiza, analiza poremećaja fluktu-acija (DFA) i višestruka korelacijska analiza (DCCA) pokazale su snažnu koherenciju između brzine i smjera vjetra sa sporo opadajućom amplitudom višednevne periodičnosti s povećanjem razdoblja pomaka. Osim izražene dnevne periodičnosti na svim lokacijama, spektralna analiza i DFA također su pokazale značajne sezonske i godišnje periodičnosti, postojanost dugog pamćenja sa sličnim karakteristikama na svim mjestima i tornjevima s relativno uskim rasponom Weibullovih parametara. DCCA ukazuje na slične uzorke vjetra na svakom tornju i jake korelacije između mjernih mjesta unatoč udaljenostima između tornjeva čak do 300 km. Područje sjeverne Nevade pokazuje veći potencijal vjetra i veću postojanost vjetra u usporedbi sa zapadno-središnjom regijom. Sveukupno, rezul-tati DFA i DCCA ukazuju na veći stupanj komplementarnosti među podacima o vjetru na različitim mjestima u usporedbi s prethodnim standardnim statističkim analizama

Modeliranje magle nad morem na obali Kalifornije u slučaju "Vruće Kaplje"

The occurrence of sea fog along the U.S. Pacific Coast in summer is frequently associated with the movement of a high pressure system from the eastern Pacific to the land. Subsequently there is strong heating of the land over several days or more and development of »hot spells« and offshore flows in the coastal region preceding sea fog formation. This study focuses on modeling the formation and evolution of sea fog in response to interaction between the warm and dry offshore flows and the cool and moist marine atmospheric boundary layer. Simulation results support a conceptual model of fog formation and evolution based on physical processes initiated by offshore flows that efficiently lower the marine inversion near the sea surface. In spite of the warm and dry advection, fog formed in the shallow, near-surface marine layer capped by a strong temperature inversion of 10 °C or more and a hot-air layer above the inversion. Prior to sea fog formation, negative surface heat flux initiates cooling and condensation, while the surface moisture flux contributes to increased humidity and turbulence within the surface layer. The dryness of the hot-air layer overlying the shallow and moist marine layer triggers enhanced radiative cooling at the marine layer top and facilitates the marine layer’s saturation. The thin cloud forms, rapidly propagates downward, and transforms into fog. As soon as the fog is formed, longwave radiative cooling at its top generates turbulent mixing and the growth of the fog as a mixed layer. Due to the fog-top radiative cooling, the fog layer is initially colder than the underlying surface. In the later stage of the fog evolution, continuous mixing of the cool and moist near-surface air with the dry and warm layer above the inversion during the fog growth generally curtails turbulence. This process elevates the lifting condensation level and can lead to sea fog dissipation or generation of stratus.Pojava magle na moru uzduž američko-pacifičke obale je često povezana s premještanjem istočno-pacifičke anticiklone na kopno. U tom slučaju prisutno je višednevno zagrijavanje kopna i razvoj »vruće kaplje« (»hot spell«) te vjetrova koji pušu s kopna na more neposredno prije pojave magle. Cilj ove studije je modeliranje stvaranja i razvoja magle na moru kao posljedice interakcije vrućeg i suhog vjetra s kopna i hladnog i vlažnog maritimnog graničnog sloja. Simulacije potvrđuju izloženi temeljni teorijski model formiranja i razvoja magle nad morem koji je temeljen na fizikalnim procesima u kojima vjetrovi s kopna spuštaju maritimnu inverziju neposredno do morske površine. Usprkos advekciji suhog i toplog zraka, magla nad morem nastaje u plitkom površinskom sloju koji je zatvoren s gornje strane s inverzijom od 10 °C(K) ili više te slojem vrućeg zraka iznad inverzije. Prije formiranja magle na moru, negativni površinski senzibilni fluks topline uzrokuje hlađenje i kondenzaciju dok latentni toplinski fluks doprinosi povećanju vlage i turbulencije u površinskom sloju. Suhoća toplog sloja zraka nad maritimnim slojem uzrokuje pojačano dugovalno radijacijsko ohlađivanje na vrhu maritimnog sloja i pospješava kondenzaciju. Isprva se formira tanki oblak koji se ubrzano razvija prema površini mora te se pretvara u maglu nad morem. Čim se magla formira, radijacijsko ohlađivanje gornje granice stvara turbulentna gibanja i razvoj magle kao sloj miješanja. Uslijed radijacijskog ohlađivanja, magla postaje u početku hladnija od površine. U kasnijoj fazi razvoja magle, stalno miješanje hladnog i vlažnog maritimnog zraka s toplim i suhim slojem iznad inverzije ograničava turbulentno miješanje. Uslijed toga podiže se visina kondenzacijskog nivoa te dolazi do razbijanja magle ili njezine transformacije u stratus

Jagadish Chandran Kaimal (Kuala Lumpur, Malaysia, 18 Nov. 1930 – New York, USA, 25 Jan. 2021)

Jagadish Chandran Kaimal - In memoriamJagadish Chandran Kaimal - In memoria

Jagadish Chandran Kaimal (Kuala Lumpur, Malaysia, 18 Nov. 1930 – New York, USA, 25 Jan. 2021)

Jagadish Chandran Kaimal - In memoriamJagadish Chandran Kaimal - In memoria

Edukacija i istraživanje: početni razvoj atmosferskog lagranžijanskog stohastičkog čestičnog modela ALPS

The Atmospheric Lagrangian Particle Stochastic (ALPS) dispersion model was created as an experimental student project and tested under idealized and complex atmospheric and topographic conditions. The challenge of the project was to bring current scientific technology to the direct involvement of students in the framework of problem based learning educational theory. The model simulates dispersion of a passive scalar in the atmosphere by calculating a large number of Lagrangian particle trajectories. It uses meteorological model output to obtain mean meteorological fields. The predicted turbulence kinetic energy (TKE) from a higher order turbulence closure nonhydrostatic meteorological model is used for the simulations. Idealized tests showed that ALPS is correctly responding to different static stability conditions and associating dispersion of particles according to the magnitude of turbulence, satisfying the well-mixed criterion.Atmosferski lagranžijanski stohastički čestični model ALPS napravljen je kao eksperimentalni studentski projekt. Testiran je u idealiziranim i kompleksnim atmosferskim i orografskim uvjetima. Cilj projekta bio je studente direktno uključiti u najnovije znanstvene tehnologije. Model simulira disperziju pasivnog skalara u atmosferi tako da računa lagranžijanske trajektorije velikog broja čestica. Za srednje vrijednosti meteoroloških polja koristi rezultate meteorološkog modela. Za simulacije koristi prognostičku turbulentnu kinetičku energiju (TKE) iz nehidrostatskog meteorološkog modela višeg reda zatvaranja. Idealizirani testovi pokazali su da ALPS dobro reagira na različite uvjete statičke stabilnosti i povezuje disperziju čestica u zavisnosti o jakosti turbulencije, pri tome zadovoljavajući kriterij dobre izmiješanosti

Edukacija i istraživanje: početni razvoj atmosferskog lagranžijanskog stohastičkog čestičnog modela ALPS

The Atmospheric Lagrangian Particle Stochastic (ALPS) dispersion model was created as an experimental student project and tested under idealized and complex atmospheric and topographic conditions. The challenge of the project was to bring current scientific technology to the direct involvement of students in the framework of problem based learning educational theory. The model simulates dispersion of a passive scalar in the atmosphere by calculating a large number of Lagrangian particle trajectories. It uses meteorological model output to obtain mean meteorological fields. The predicted turbulence kinetic energy (TKE) from a higher order turbulence closure nonhydrostatic meteorological model is used for the simulations. Idealized tests showed that ALPS is correctly responding to different static stability conditions and associating dispersion of particles according to the magnitude of turbulence, satisfying the well-mixed criterion.Atmosferski lagranžijanski stohastički čestični model ALPS napravljen je kao eksperimentalni studentski projekt. Testiran je u idealiziranim i kompleksnim atmosferskim i orografskim uvjetima. Cilj projekta bio je studente direktno uključiti u najnovije znanstvene tehnologije. Model simulira disperziju pasivnog skalara u atmosferi tako da računa lagranžijanske trajektorije velikog broja čestica. Za srednje vrijednosti meteoroloških polja koristi rezultate meteorološkog modela. Za simulacije koristi prognostičku turbulentnu kinetičku energiju (TKE) iz nehidrostatskog meteorološkog modela višeg reda zatvaranja. Idealizirani testovi pokazali su da ALPS dobro reagira na različite uvjete statičke stabilnosti i povezuje disperziju čestica u zavisnosti o jakosti turbulencije, pri tome zadovoljavajući kriterij dobre izmiješanosti

Model efekata radijacijskog prijenosa topline u graničnom sloju atmosfere

During nighttime clear-sky conditions and in the absence of significant advection the influence of divergence of net longwave radiative flux on thermodynamic processes could be dominant in the atmospheric boundary layer. The model which parameterizes such processes by height (35 grid points up to 2000 m) is accomplished based on the emissivity concept. The test of the model is performed on the Wangara experiment data. The results are analyzed and discussed concerning a complex structure of the total cooling rate, especially in the lower part of the nocturnal boundary layer (region of smaller wind speeds)

The cooling rates comparison between the longwave radiation and turbulence in nocturnal planetary boundary layer

It is shown that the process of the air-cooling is dominated by the divergence of the longwave radiative flux in cases of night-time clear-sky conditions and with weak wind conditions. The parameterization of the longwave radiative flux divergence is derived according to the emissivity concept and the Stefan-Boltzman law, assuming that the water vapor is the only absorber of longwave radiative. The parameterization of the turbulent temperature flux divergence has been based on the O’Brien’s K-profile. In a very short time increment, the effect of the turbulence is probably greater than the radiative effect, but very stable conditions and the absence of significant advection during the night change this hierarchy, and pure longwave radiative effect, like a slow-diffusive process, prevail in the total cooling rate according to the theory and experiments. The model was tested on the Wangara experiment data. The model results agree well with observations, measurements and numerical simulations made by other authors