21 research outputs found
Model proraÄuna prizemnih koncentracija
U CMI RHMZ Hrvatske izraÄen je model za pruraÄun prizemnih koncentracija polutanata u okoliÅ”u poviÅ”enog i prizemnog izvora emisije. Model je gausovskog tipa. Ulazni parametri su satne vrijednosti brzine i smjera vjetra, stabilnosti zraka i visine sloja mijeÅ”anja. Algoritam modela ukljuÄuje i sluÄajeve "tiÅ”ina" kao
i modifikaciju lateralne difuzije kod slabih vjetrova
VERTICAL EDDY POLLUTANT FLUX IN URBAN CONDITIONS
A method has been proposed for deriving the vertical turbulent flux of light, chemically inert pollutant from meteorological and urban parameters which are easily available. Based on the flux-gradient theory and a division of urban volume in UCL (Urban Canopy Layer) and UBL (Urban Boundary Layer) an iterative procedure has been adopted for the pollutant flux estimation with urban-sensible heat and surface roughness as the basic input. The method has been applied to a range of possible urban characteristics known from existing literature. It came out that the influence of surface roughness upon pollutant turbulent vertical fluxes predominated in all stabilities and also that it was rather insensitive of UCL height. Besides, theoretical speculations found turbulent vertical fluxes of pollutants considerably weaker than turbulent fluxes of momentum
TESTIRANJE CMI MODELA TEÅ KIH PLINOVA
Na bazi eksperimenta izvrÅ”eno je testiranje modela teÅ”kih plinova, izraÄenog u Centru za meteoroloÅ”ka istraživanja RepubliÄkog hidrometeoroloÅ”kog zavoda SRH. U uvjetima neutralne ili malo stabilne (i labilne) stratifikacije model proraÄunava koncentracije u prihvatljivim granicama. Kod veoma nestabilne atmosfere model potcjenjuje, dok kod ekstremno stabilne atmoslere model precjenjuje. Uzrok tome je nedovoljno precizno odreÄena stabilnost u najnižim slojevima (prvih par metara uz tlo), gdje se teÅ”ki plin (H2S) rasprostire
Jednodomenzionalna spektralna analiza razvoja raspoložive potencijalne energije perturbacija iznad ograniÄenog podruÄja
The paper describes development processes on their energetic basis. A special emphasis is given to the role of the eddy available potential energy, Ae arising out of zonal available potential energy, AZ. The process of energy transition C(AZ Ae) can be estimated in the wave number domain by means of a cospectral function fn(H,T) of the isobaric surface height H and the temperature T. IN cases of baroclinic instability prevalence, the fn(H,T), if determined along a cross-sectional line over a limited region, may help the forecast of a given eddy scale development, relevant for that region
The significance of recent climatic fluctuations at Zagreb
A significance of climatic fluctuations in northwestern Croatia has been investigated by means of autocorrelations in the meteorological data series. The test has been applied to the filtered series of temperature, solar radiation, cloudiness, air pressure and precipitation at Zagreb-GriÄ observatory and it has confirmed a significant climatic fluctuation of air temperature, solar radiation and cloudiness. Stochastic correlations amongst these climatic elements revealed a dominant influence of cloudiness and solar radiation upon the temperature climatic normals at Zagreb
Procjena difuzije zs vrijeme tiŔina
U radu je opisana metoda odreÄivanja koeficijenata difuzije za vrijeme tiÅ”ina pomoÄu P-G krivulja stabilnosti. Njihovim ukljuÄivanjem u model tiÅ”ina od Okamoto i Shiozawe dobija se moguÄnost proraÄuna koncentracija za vrijeme tiÅ”ina u onim lokalitetima, gdje je pogodna primjena gausovskog modela
Analiza zagrebaÄkih klimatoloÅ”kih nizova pomoÄu empirijski odreÄenih prirodnih sastavnih funkcija
The empirical mode decomposition method (EMD) (Huang, 1998) is applied
to the series of annual and seasonal averages of temperature, cloudiness,
air pressure and annual and seasonal sums of global radiation and precipitation,
all observed in Zagreb-Gri~ in the period 1862ā2002. The method
itself decomposes the original series into so called intrincic mode functions
(IMF), each being characterized by its own, intrinsic time scale.
Sums of the low-frequency IMFs for the single element revealed present
climatic fluctuations on the decade-to-century scale. It is confirmed that
climatic fluctuations of every single element, particularly temperature and
cloudiness, are the results of variations in the global atmospheric circulation
above the whole Europe. Trend and long-term variations of Zagreb temperature
fits to globally observed increase of temperature but also to variations
of zonal circulation index. Exchange of Hadleyās zonal and Rossbyās wave regime
of the general atmospheric circulation at the beginning of the 20th century
is observed in the long-term variations of almost every element. Linear
correlation coefficients between annual and seasonal long-term variations
are calculated. It is shown that spring and winter variations mostly influenced
annual fluctuations that is due to internal feed-back processes.
Also, correlation coefficients for every pair of climatic element are calculated,
enabling conclusions about interaction between elements on long-term
scales.Metoda empirijskog rastavljanja (engl. empirical mode ecomposition) EMD, (Huang, 1998) primjenjena je na godiÅ”nje i sezonske nizove srednjaka temperature, tlaka, naoblake te godiÅ”nje i sezonske sume globalnog zraÄenja i koliÄine oborine mjerene u Zagrebu-GriÄ, za razdoblje 1862ā2002. Metoda rastavlja originalne nizove na tzv. prirodne sastavne funkcije, intrinsic mode functions (IMFs), od kojih je svaka karakterizirana svojstvenom vremenskom skalom.
MeÄusobnom superpozicijom dugoperiodiÄnih prirodnih sastavnih funkcija pojedinog elementa uoÄena je prisutnost klimatskih fluktuacija. PotvrÄeno je kako su klimatske fluktuacije svakog pojedinog elementa, posebno temperature i naoblake,
rezultat varijacija opÄe cirkulacije atmosfere nad cijelom Europom. Trend i dugoperiodiÄke varijacije zagrebaÄke temperature dobro odgovaraju globalnom trendu opÄeg porasta temperature, ali i varijacijama zonalnog cirkulacionog indeksa. Pretpostavljena
izmjena Hadleyevog zonalnog i Rossbyevog valnog režima opÄe cirkulacije atmosfere poÄetkom 20. stoljeÄa oÄituje se u dugoperiodiÄkim varijacijama gotovo svih
elemenata. IzraÄunati su koeficijenti linearne korelacije izmeÄu godiÅ”njih i sezonskih dugoperiodiÄnih varijacija te je pokazano kako se proljetne i zimske varijacije veÄine elemenata osjetno odražavaju na fluktuacije godiÅ”njih srednjaka, Å”to je u skladu s
dominacijom internih procesa povratne sprege (engl. feed back). TakoÄer su izraÄunati koeficijenti korelacija izmeÄu svaka dva klimatska elementa {to je omoguÄilo zakljuÄke o interakcijama meÄu elementima na dugoroÄnoj skali
Kumulativne razdiobe koncentracija u verifikaciji modela difuzije
Testiran je gausovski model za toÄkasti poviÅ”eni izvor SO2 u orografski razvijenom podruÄju. UsporeÄene su kumulativne razdiobe izraÄunatih koncentracija i koncentracija izmjerenih monitorom na Äetiri lokacije u blizini izvora. IzraÄunata je korelacija izmeÄu kumulativnih krivulja koja pokazuje dobro slaganje teoretskih i mjerenih vrijednosti. Omjer teoretskih i izmjernih vrijednosti ukazuje na prilagodbu modela orografskim uvjetima
Neke osobine hidrodinamiÄke nestabilnosti u kvazigeostrofiÄkoj atmosferi
The baroclinic hydrodynamic instability of zonal flow has been studied by a two-level model which takes into account the influence of a barotropic, nonlinear shear in a quasigeostrophic atmosphere. There are regions where a horizontal wind shear supports the baroclinic amplification of an unstable wave. It can be found near the inflexional part of the zonal flow meridional profile
ENERGETSKA RAVNOTEŽA PRIZEMNOG SLOJA ATMOSFERA -TLO U HRVATSKOJ
Komponente energetske ravnoteže prizemnog sloja atmosfere izraÄunate su metodom Bydyka pomoÄu srednjih mjeseÄnih vrijednosti (razdoblje 1949-73) meteoroloÅ”kih elemenata na 29 meteoroloÅ”kih stanica u SR Hrvatskoj. To su: neto fluks radijacije R, latentna toplina isparavanja LE, turbulentna razmjena topline P i fluks topline u tlu B. Te veliÄine su baza jedne klimatske podjele Hrvatske. Ujedno je pronadjena korelacija izmedju P, LE i B te srednjeg temperaturnog režima kao i razvoja konvektivne naoblake