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Temperatura malog duguljastog jezera (2,3 km × 0,1–0,6 km; maksimalna dubina od 46 m) smještenog u brdsko-planinskom području mjerena je tijekom tri razdoblja od srpnja do rujna u blizini jezerske površine (dubina od 0,2 m). Istovremeno su u blizini jezera mjerene standardne meteorološke varijable. Na temelju atmosferskih i jezerskih uvjeta definirani su kriteriji za detekciju dana s perzistentnim povjetarcem (LLB). Rezultati su pokazali da se u 17,7% ispitanih dana nad jezerom uspostavljao povjetarac. Svi ti dani bili su popraćeni s povišenom energijom u normaliziranom valićnom spektru brzine vjetra pri periodu od 24 sata. Dnevni povjetarac s jezera najčešće je zbog okolne topografije bio kanaliziran u smjeru glavne osi jezera. Sukladno tome, dnevno anticiklonalno zakretanje vjetra bilo je poremećeno. Međutim, noću je bila izražena rotacija vjetra u smjeru kazaljke na satu. Nadalje, rezultati su pokazali jasnu vezu između jačine povjetarca i razlike temperature zraka nad tlom i nad jezerom., The temperature of a small elongated lake (2.3 km by 0.1-0.6 km; maximum depth of 46 m) located in a mountaneous area was measured during July-September period over three years (2018-2020) at the depth close to the lake surface (0.2 m). Concurrent standard meteorological variables were measured in the vicinity of the lake. Criteria based on atmospheric and lake conditions were defined to detect the days with persistent lake-land breeze (LLB) events. The results showed that 17.7% of the investigated days were associated with LLB events. These days were accompanied by elevated energy in the normalized wavelet spectra for the wind speed at period of 24 hours. Daytime onshore lake breezes were mainly channeled in the along-lake direction due to the surrounding topography. Accordingly, during the daytime, diurnal wind veering was distorted. However, during the nighttime, a clear clockwise wind rotation was present. In addition, the results exhibited a clear relationship between the lake-land temperature difference and the strength of the LLBs.

Same as ocean-atmosphere interactions, two-way interactions between lakes and the atmosphere occur through fluxes in momentum, heat, moisture and mass at water surfaces, modifying thus weather and climate of their surrounding areas. In the present study, we investigated two types of these interactions: 1) the response of a small, elongated, temperate lake (Kozjak, Plitvice Lakes ; the lake fetch is 2.3 km, and the maximum depth is 46 m) to atmospheric forcing ; and 2) the atmospheric response to the presence of the same lake, i.e., the occurrence of a thermal, lake-land breeze circulation. Three-year time series of observed data (specifically, standard meteorological data and lake-temperature experiment data with the temporal resolutions of 1 h and 2 min, respectively) were analyzed. In addition to the standard statistical procedures, spectral and wavelet analyses were employed. It is shown that due to the atmospheric forcing, the lake stratifies during the warm part of a year with a thermocline deepening from spring to late fall. Additionally, if the lake is stratified and the sirocco wind blows above the Adriatic, internal standing waves (internal seiches) occur within the lake. Under undisturbed atmospheric conditions, atmospheric response to the lake presence is seen as an establishment of a lake- land breeze circulation despite the small lake size. In contrast to findings for the Lake Garda, results of this study suggested a clear relationship between the lake-land temperature difference and the strength of breezes.

Water temperature directly influences a range of lake properties such as the solubility of gases and minerals or the rate of chemical reactions. The vertical water temperature profile determines the water column stability and has a significant role in the vertical transport of gases and nutrients, consequently affecting the biological activity and diversity in the lake. The thermodynamic behavior of lakes is affected by many processes including shortwave and longwave radiation, attenuation of light, sensitive and latent heat flux, sediment heat flux, phase change of water, convective and turbulent mixing, and wind sheltering. However, the main driver are the meteorological conditions determining the heat flux at the lake surface. Here, a simple 1-D energy budget model (SIMO) for the prediction of the vertical temperature profiles in small, monomictic lakes is proposed. The goal was to develop a model that estimates the net heat flux and vertical thermal diffusion using only routinely measured hourly mean meteorological variables. Namely, the proposed model employs carefully chosen parameterizations to calculate surface heat flux components, such as longwave and shortwave radiation, using only the air temperature, relative humidity, atmospheric pressure, wind speed, precipitation and ultraviolet B radiation (UVB). The only additional data needed are the climatological yearly mean air temperature data. Except for the initial vertical temperature profile, the model does not use any lake-specific variables. The model performance was evaluated against lake temperatures measured continuously during an observational campaign in two lakes belonging to the Plitvice Lakes, Croatia (Prošće and Kozjak). Temperatures were measured at 15 and 16 depths ranging from 0.2 to 27 in Prošće (maximum depth of 37.4 m) and 0.2 to 43 m in Kozjak (maximum depth of 46 m). Common bivariate measures were used: mean bias error, mean absolute error, root mean square error and maximum absolute error, as well as index of agreement. Results from simulations of different lengths, ranging from 1 to 30 days, were used to evaluate the model performance sensitivity to the simulation length. The model performed reasonably well and it was able to satisfactorily reproduce the vertical temperature profile at the hourly scale, the deepening of the thermocline with time, and the annual variation in the vertical temperature profile. The ability of the model to predict the springtime onset of lake stratification and autumn convective overturn was also examined by running a yearlong simulation initiated with an approximately constant vertical profile of the lake temperature (~ 4°C). The model was able to reproduce the lake stratification. The upper limit of the metalimnion was well captured while it‟s thickness was overestimated. The epilimnion temperature was also somewhat overestimated. Nevertheless, the values of the model performance measures of the yearlong simulation were comparable with those reported for other more complex models. This shows that the presented model can be used for assessment of the onset and duration of lake stratification periods when no water temperature data are available, as well as for long term simulations for climate change impacts assessment.

The aim of the study was to investigate if a small, elongated lake (Kozjak, Plitvice Lakes, Croatia ; 2.3 km by 0.1-0.6 km ; maximum depth of 46 m) can produce atmospheric thermal circulation systems, that is, lake-land breezes (LLBs). The lake temperature was measured during summertime over three years (2018-2020) at the depth of 0.2 m at temporal resolution of 1h. Simultaneous standard meteorological variables were obtained from nearby meteorological site. Days with persistent LLBs were identified based on 7 prescribed criteria in which the atmospheric and lake conditions were taken into account. Specifically, these criteria take into account air and lake temperature, wind speed and direction, air pressure and precipitation. The results show that despite of the small lake size, LLBs were established. Thus, 17.7% of the investigated days were associated with persistent LLB events. As these events were accompanied by elevated energy in the normalized wavelet spectra for the wind speed at period of 24 hours, it was concluded that the prescribed criteria well define persistent LLB events. However, it was noted that the observed LLBs were most likely superposed with the thermally induced up- and downslope winds, as Kozjak Lake is confined by nearby mountains. While during the nighttime, land breezes were characterized with a clear clockwise wind rotation, during the daytime, lake breezes were frequently channeled in the along-lake direction due to the surrounding topography. Finally, the results showed a clear relationship between the lake-land temperature difference and the strength of the LLBs.

During winters, residents of Dugave, Zagreb are according to media, frequently upset about the air quality in the quarter. Therefore, we investigated the air quality there with respect to particulate matter with aerodynamic diameter less than 10 μm (PM10). Hourly mean PM10 concentrations were measured over three years (2018–2020) at Dugave measuring site (ZG3, ϕ = 45.765°N, λ = 16.006°E). The site belongs to the National Network for Continuous Air Quality Monitoring (NNCAQM) and it is supposed to be representative for urban background conditions. Concentrations measured at ZG3 were compared with PM10 values that were observed at NNCAQM measuring site exposed to urban traffic (Miramarska, ZG1, ϕ = 45.800°N, λ = 15.974°E). The influence of meteorological conditions on PM10 levels at both sites was assessed based on modelled atmospheric variables, where a numerical weather prediction model ALADIN was employed. The results showed that although overall median and maximum hourly concentrations were slightly lower at ZG3, the mean concentration at ZG3 was somewhat higher than at ZG1 (30.28 and 29.28 μgm-3 , respectively). During spring, summer and fall, PM10 concentrations at ZG3 were generally similar to or slightly lower than those at ZG1, while during the winter, they were higher. This suggests that in comparison with ZG1 site, ZG3 was more exposed to: 1) effects of fossil fuel and/or biomass burning due to heating ; and/or 2) atmospheric inversions. At both sites and for all four seasons, PM10 concentrations decreased with an increase in a wind speed, where this decrease was the most pronounced for wintertime at ZG3. For both sites, an increase in the air temperature resulted in a decrease in PM10 concentrations in all seasons except summer. A decrease of concentration with an increase in temperature was most prominent for winter, and this drop was more significant for ZG3 in comparison with ZG1 site. This further confirms our hypothesis that wintertime pollution at ZG3 was more affected by emissions associated with burning due to heating and/or unfavorable microclimatic conditions than ZG1 site. Conversely, in summer, PM10 concentrations at both sites increased with an increase in the air temperature. This points to the role of photochemical reactions in particle formation. Accordingly, this increase was more pronounced at the urban traffic site, that is, at the site where higher emissions of particulate matter precursors is expected. At both sites, the daily PM10 concentration limit value given by EU legislative (50 μgm-3 ) was exceeded more frequently than permitted, that is, more than 35 times in a year. Thus, at ZG1, 59 and 36 days with the mean concentration above the limit were observed in 2018 and 2019, respectively. At ZG3, the exceedance was even more frequent and it was found for all three years. Daily values above the limit were observed 56 and 63 times for 2018 and 2019, respectively. For 2020, the November and December data were missing. Still, during the available 10-month period, daily concentrations above the 50 μgm-3 limit were observed 37 times.

We investigated the impact of meteorological conditions and number of visitors on the atmospheric particulate matter (PM) mass concentrations and particle fraction ratios at the Plitvice Lakes National Park during summer and fall of 2018. Outdoor concentrations of particles with an aerodynamic diameters less than 1 µm, 2.5 µm and 10 µm (PM1, PM2.5, and PM10, respectively) were measured by a light- scattering laser photometer. The photometer was placed at the meteorological measuring site for which concurrent meteorological data were available. Another photometer recorded only the PM1 fraction in the nearby office of the National Park. Apart from standard statistical methods, the Openair software, which was developed specifically for the analysis of air quality data, and spectral analysis based on weighted overlapped segment averaging (WOSA) method were applied. Results showed an increase in mass concentration with the increase of number of visitors and the air temperature for all measured PM fractions. The latter, together with the decrease of PM1/PM2.5 ratio with an increase of temperature, pointed to the importance of photochemical reactions in the production and growth of particles. Furthermore, outdoor PM concentrations and PM1/PM2.5 and PM2.5/PM10 ratios decreased as the wind speed increased. As seen from bivariate polar plots, the highest and the lowest PM1/PM2.5 and PM2.5/PM10 ratios were associated with winds from the north-western and south-eastern quadrant, respectively. Apart from the diurnal periodicity of both PM and meteorological time series, a period of ≈ 25 min was present in the PM10 spectrum. This period was very likely associated with particle emissions and resuspensions due to diesel- powered tourist vehicles. While weekly periodicity was present in average weekly courses of all fractions of particulate matter, it was not accompanied by expected peaks in the PM spectra.

Within the project "Hydrodynamic Modeling of the Plitvice Lakes System", a hydrodynamic model of Prošćansko Lake was developed in order to facilitate management of water resources that are part of the protected area. The hydrodynamic model describes the physical processes that occur in the lake and at the water-air boundary. Shallow lakes respond quickly to atmospheric changes and forcing, so it is necessary to use an appropriate model that describes the processes of heat exchange at the water-air boundary, the processes of vertical mixing and turbulent energy transport between layers of the lake. Therefore, the 3D hydrodynamic model SCHISM (Semi-implicit Cross- scale Hydroscience Integrated System Model, Zhang et al.) was chosen. The model simulated the influence of atmospheric conditions above the lake of complex bathymetry and their coupling with the physical processes in the lake to gain insight into the thermal structure, currents, and changes in elevation of the lake. By adjusting various input variables (meteorological/hydrological data), model parameters (bottom friction coefficient, diffusion coefficients, albedo, windfactor, watertype), structuring the networks of different configurations, correctly selecting the numerically algorithms and the turbulent closure scheme, a good correlation between the model output variables (change in lake elevation and 3D temperature field) and measured values was reached.

Investigation of Thermal Stratification of a Lake Based on Low-cost Observational Data Thermal stratification can be established in deep mid-latitude lakes, being related to surface heating during the warm part of a year. Due to separation of lake into distinct vertical layers and inhibition of vertical mixing, stratification may affect hydrogeochemical and biological conditions in a lake. Here, we investigate thermal stratification of the 46 m deep lake (Kozjak, Croatia) at fine temporal and vertical resolution. The lake is the twelfth and the largest one (area 0.82 km2, volume 0.01271 km3) in the chain of sixteen karstic Plitvice Lakes interconnected by cascades and waterfalls. Fifteen waterproof temperature sensors with data loggers (HOBO TidBit 400, measurement accuracy of ±0.20°C for temperatures between 0° and 70°C) were fixed to a string at depths ranging from 0.2 m to 43 m. The string was attached to a buoy which was moored to ensure its steady position in the deepest part of the lake (φ = 44.89°, λ = 15.60°). Analysis of temperatures observed at 2-min temporal resolution during 6 July – 5 November 2018 revealed thermocline deepening from about 8 m (July) to about 15 m (end of October). Furthermore, diurnal variation of water temperature, density and Brunt–Väisälä frequency was found in the uppermost, approximately 3 m deep layer and in concurrent meteorological data. Power spectrum densities computed for lake temperatures suggest periods of 8.3 min and 5-6 h at depths ranging from 9 to 17 m and from 17 to 23 m, respectively.

The turbulence characteristics of flows over heterogeneous and patchy vegetation still present an ongoing issue, mainly due to the lack of experimental results. In this study we focus on turbulence spectral characteristics, dissipation rate of turbulent kinetic energy (TKE) and budgets of the TKE in the wintertime, night-time boundary layer over inhomogeneous surface. Measurements from a tall mast which was situated in a small deciduous forest were analysed. Measurements at five levels above the canopy height (approximately h=18 m) were influenced by the upwind conditions which represent different types of surfaces. In this study we focus on the combined influence of the roughness sublayer (RSL) found above tall vegetation and the internal boundary layer (IBL). Results showed that horizontal velocity spectra have the predicted -5/3 slope in the high- frequency range indicating the existence of the inertial subrange at the upper four levels (z>1.5h), but the same is not found for the vertical wind spectra. The lowermost level (2 m above the canopy) is clearly influenced by the roughness elements showing that on average there is no well-defined inertial subrange. Testing the local isotropy hypothesis more thoroughly resulted in a ratio of the horizontal spectral densities (Sv/Su) approaching the 4/3, while the ratio of the vertical to the longitudinal spectral density (Sw/Su) was less than 1 for all levels indicating an anisotropic turbulence above the canopy. The vertical velocity spectra have deviations for the inertial subrange and this is investigated in more detail. We found that an appropriate stability function for the non-dimensional dissipation of TKE calculated from spectra in the inertial subrange differs from the classical linear function obtained for the Kansas data. We compared our results with the empirical models of Kaimal et al. (Q J R Meteorol Soc 98:563– 589, 1972) and Olesen et al. (Boundary-Layer Meteorol 29: 285–312, 1984). Using Kaimal's model, normalized spectra show that -2/3 slope is followed quite closely for a wide range of frequencies in the inertial subrange. The stability has an important effect on turbulence spectral structure and also on frequencies of spectral peaks. Extending the analysis to the Olesen approach, normalized spectra collapse to one single curve. Finally, analysing the budget terms of the turbulent kinetic energy non- equilibrium conditions are found.

A proper representation of turbulence is particularly important for parameterization of surface-atmosphere exchange processes in atmospheric models (e.g., dispersion, numerical weather prediction or regional models). These models use similarity scaling to model flow characteristics and dispersion. In this study we investigate the applicability of Nieuwstadt's (1984) local scaling formulation for the stable boundary layer over a truly heterogeneous terrain. It is well known that even modest surface heterogeneity can significantly influence the nocturnal boundary layer (NBL) and lead to turbulence at higher Richardson number in comparison with homogeneous surfaces. Therefore, this study relates to the approach of Grachev et al. (2013), who distinguished between Kolmogorov and non-Kolmogorov turbulence. Here we evaluate local similarity scaling in terms of flux- variance and flux-gradient relationships. The data for this study stem from a tall tower within a small forest patch situated in heterogeneous terrain influenced by a mixture of forest, agricultural and industrial surfaces in different upwind sectors. The 62 m tower (levels 20, 32, 40, 55 and 62 m above ground) was situated in the middle of some 120 m x 480 m area of 18 m high trees. The heterogeneity of the surface was characterized by spatial variability of both roughness and topography. The analysis shows that local similarity approach is valid at a forested site with highly inhomogeneous fetch. It was found that flux-variance and flux-gradient relationships respond differently to inhomogeneity. While the roughness sublayer influence was observed for the flux-variance relationships, it did not show any significant effect on dimensionless wind shear (Φm). Despite the inhomogeneous surface conditions, flux-gradient relationship showed similar distinction between Kolmogorov and non-Kolmogorov turbulence as found under ideal conditions. After removing data points associated with the flux Richardson number (Rf) greater than 0.25 (supercritical regime), dimensionless wind shear supports classical linear expressions even over inhomogeneous terrain. Deviations from linear expressions were found to be mainly due to the small-scale turbulence rather than due to the surface heterogeneities.

In this study we investigate the applicability of Nieuwstadt's (1984) local scaling formulation for the stable boundary layer using the data from a 62 m tall tower (levels 20, 32, 40, 55 and 62 m above ground) within a small forest patch situated in the vicinity of town Kutina in heterogeneous terrain with agricultural land, forested hills, industrial and urban surfaces in different upwind sectors. We only analyze periods with stable stratification from winter 2008/2009 focusing on the influence of different wind directions, accounting for different surface characteristics, and different wind regimes. The large-scale forcing was classified into three wind regimes, namely, weak, intermediate and strong winds. We adopt local scaling approach for which similarity functions and the local stability parameter are based on local fluxes at measurement height. In the data analysis the role of self-correlation is examined. Values of scaled standard deviation for wind components in near-neutral conditions are found to be lower at the lowest measurement level and higher at upper levels in comparison to canonical Kansas values. The non-dimensional gradient of wind velocity is also investigated. It is found that the stability function for momentum supports the linear equation only up to values of the non-dimensional stability parameter ζ = 0.5. Moreover, we find good agreement between our results and the Beljaars and Holtslag function, which increases more slowly with increasing stability. Our analysis supports the validity of z-less stratification for very stable conditions (ζ > 1) for scaled wind velocity variances and correlation coefficients for momentum and heat flux. As a preliminary conclusion it is found that local scaling is promising even over highly non-homogeneous terrain as in our case.

Atmosferske lebdeće čestice su krute ili tekuće čestice promjera do 100 µm raspršene u zraku. Po nastanku, kemijskom sastavu i fizičkim osobinama lebdeće čestice su vrlo raznolike, a općenito mogu utjecati na vrijeme, klimu, vidljivost i ljudsko zdravlje. U Geofizičkom odsjeku PMF-a su tijekom višemjesečnog zimskog razdoblja dvama laserskim fotometrima (DUSTTRAK Aerosol Monitor TSI, Shoreview, SAD) mjerene masene koncentracije atmosferskih lebdećih čestica promjera do 1 µm (PM1). Otvori oba instrumenata nalazili su se na 1.7 m nad tlom što približno odgovara prosječnoj udisajnoj visini. Istovremeno su se u blizini mjernih mjesta prikupljali i vanjski meteorološki podaci. Tijekom eksperimenta unutar zgrade odvijale su se uobičajene aktivnosti. Rezultati pokazuju da koncentracije PM1 izmjerene unutar zgrade ovise o vanjskim meteorološkim uvjetima. Nadalje, ovisnost koncentracija unutar zgrade o pojedinim smjerovima vjetra ukazuje na mogući utjecaj 8 – 9 km udaljene industrijske zone Zagreba. U mjerenim koncentracijama se također uočava i poludnevna i dnevna periodičnost te dugoperiodička (10 – 11 dana i oko 21 dan) promjenjivost.

Due to the development (or presence) of internal boundary layers the turbulent characteristics in the lowest meters over heterogeneous surfaces are more complex than above horizontally homogeneous and flat terrain. In this study we investigate the applicability of Nieuwstadt's (1984) local scaling formulation for the stable boundary layer. The data for this study stem from a tall tower within a small forest patch situated in heterogeneous terrain with agricultural land, forested hills and urban surfaces in different upwind sectors. The 62 m tower (levels 20, 32, 40, 55 and 62 m above ground) was situated in the middle of some 120 m x 480 m area of 18 m high trees. Here we only analyze periods with stable stratification from winter 2008/2009 focusing on the influence of the upwind hilly terrain. As turbulent fluxes showed a substantial variation with height, we adopt local scaling approach for which similarity functions and the local stability parameter are based on local fluxes at measurement height. In the data analysis the role of self-correlation is examined. Also an in-depth error analysis applying the Filtering Method allows to estimate the percentage of random errors in the turbulence variables. Using this method it is possible to inspect if the scatter in the measurements is caused by random errors, or by other dynamical factors of the stable boundary layer. Values of scaled standard deviation for wind components in near-neutral conditions are found to be lower at the lowest measurement level and higher at upper levels in comparison to canonical Kansas values. The non-dimensional gradient of wind velocity is also investigated. We compare our results with traditional linear equations for the stable case and also to the empirical non-linear expression proposed by Beljaars and Holtslag (1991). It is found that the stability function for momentum supports the linear equation only up to values of the non-dimensional stability parameter ζ ≈ 0.5. Moreover, we find good agreement between our results and the Beljaars and Holtslag function, which increases more slowly with increasing stability. As we observed more strongly stable stationary cases, local z-less scaling is also addressed. Our analysis supports the validity of z-less stratification for very stable conditions (ζ > 1) for scaled wind velocity variances and correlation coefficients for momentum and heat flux. As a preliminary conclusion, based on scaled velocity variances and non-dimensional mean wind shear, it is found that local scaling is promising even over highly non-homogeneous terrain as in our case.

We investigated the relationship between indoor short-term (1-min mean) particulate matter (PM) mass concentrations and outdoor 1-min mean meteorological conditions. Indoor PM mass concentrations, namely particles having aerodynamic diameters less than or equal to 1 m (PM1), 2.5 m (PM2.5), 4 m (PM4), 10 m (PM10) and total suspended particular matter (TPM) were measured at the Department of Geophysics, Faculty of Science, University of Zagreb, Zagreb, Croatia for the period 12 December 2012 – 26 April 2013. Two DUSTTRAKTM Aerosol Monitors (TSI, Inc., Shoreview, MN, USA), one Model 8520 and the other Model 8533, were placed 1.67 m above the floor, so their inlets corresponded to the average breathing height of 1.7 m. Both monitors were placed in building corridors, adjacent to the stair case. The model 8520, which recorded solely PM1 1-min mean mass concentrations, was placed on the ground floor, while the model 8533, which simultaneously recorded PM1, PM2.5, PM4, PM10 and TPM 1-min mean mass concentrations, was on the first floor. The measuring site is in a residential area of northern Zagreb, approximately 1.5 km north- northeast of the city centre and 8-9 km northwest of Zagreb's industrial zone. Meteorological variables (specifically, 1-min mean surface air temperature, air pressure, relative humidity, global radiation, and three-dimensional wind) were measured in the vicinity of the Department of Geophysics building. It is shown that the PM1 fraction is the largest contributor to indoor TPM, where 51.5 m m-3 and 54.8 m m-3 correspond to the average PM1 and TPM first floor indoor wintertime mass concentrations, respectively. In addition, indoor mass concentrations of all fractions decrease with an increase in precipitation intensity, and outdoor temperature. Considering horizontal wind speed, indoor concentrations for all fractions decrease with an increase of the ambient wind speed, except for the strongest wind speeds. Results clearly exhibit an increase of indoor mass concentrations with the increase of surface air pressure and outdoor relative humidity. Furthermore, indoor PM levels depend on outdoor wind directions with concentrations of all fractions being the highest for ambient southeastern winds. This suggests advection of particles from the industrial zone toward the measuring site and the penetration of particles indoors.

In this work we investigate physically relevant timescales associated with the nocturnal, wintertime boundary layer. Cold nights with weak winds favor development of very stable boundary layer (SBL), in which a disconnection between the surface and the upper portion of the boundary layer can occur. Besides, temporal variability of turbulence in the very SBL is characterized by nonstationarity and intermittency, which both can affect computed turbulence fluxes at scales larger than the turbulence scale. Moreover, turbulence fluxes within the SBL are small and can easily be affected by the sub- and mesoscale fluxes. In such case, it is hard to distinguish the turbulence from nonturbulent motions in Fourier spectra and cospectra. To decompose instantaneous signal into mean and turbulent parts, we apply four different methods. Two of them are based on Fourier spectral analysis and two on wavelet analysis. Analyses are performed on high frequency wind and temperature datasets collected at 7 different levels within a ground-based 62 m deep layer. The measurement tower is located in the heterogeneous surroundings, which can significantly influence the turbulence characteristics of the SBL. Depending on the wind direction, measured data can capture rural, suburban or urban signatures. The mesoscale spectral energy gap in the SBL is often not found since there is no clear separation between the scales. In such case, the timescales are calculated based on the location of the maximum in the ogive of the sensible heat flux cospectra or, based on the location of a zero crossing in the multiresolution decomposition of the sensible heat flux. In addition, a wavelet analysis is applied to time series in order to yield the information about the temporal locations of different features characterized by different frequencies. All of this gives us some insights into the timescales (i.e., different physical processes) that influence turbulence characteristics associated with different land-use setups and for a range of stability conditions (from weak to strong stability) at our measurement site.

This talk focuses on the Croatian anthropogenic emissions of pollutants. An overview of estimated source apportionment for the main pollutants (gaseous, particulates, heavy metals and persistent organic compounds) is also given, as well as a list of the main individual SO2, NOx and CO sources. Finally, several recent incidents characterized with a very high, or even unlawful emissions are discussed.

The fate of pollutants in the boundary layer is strongly affected by turbulence which is extremely complicated in the complex terrain and over heterogeneous landscapes. The stable boundary layer (SBL) is generally favorable for establishment of air pollution episodes. Therefore, investigations of its characteristics are of the great importance. In this work we investigate turbulence characteristics in the stable, wintertime nocturnal boundary layer over inhomogeneous surface. We analyze data measured at five levels of 62 m high mast located near the industrial town of Kutina. Kutina is located at the southern slopes of the afforested Moslavacka Mountain in the hilly region of Moslavina, Croatia. The mast is located in the vicinity of a petrochemical plant, which is the main source of the pollution in the area. The measurement tower is placed over the heterogeneous surface, surrounded by approximately 20 m high trees. The closest trees are 20 to 30 m away from the tower. Wind data were collected by five WindMaster ultrasonic anemometers (Gill Instruments), which were installed at heights of 20, 32, 40, 55 and 62 m. Each of the sonic anemometers measured three wind components and sonic temperature at a sampling frequency of 20 Hz. Since our intention was to capture highly stable situations, we analyze the wintertime, nighttime data collected during December 2008 – February 2009 period. Here we address the issue of selecting the averaging time scale used for separation of turbulent perturbation from the mean flow, which is appropriate for the nocturnal, stable conditions. This scale is determined by applying several methods widely used in the literature. Preliminary results based on the case study analysis, which were obtained previously for the same location, suggest turbulence averaging time scales between 7 and 11.5 minutes and local maximums of vertical momentum flux and kinematic heat flux at the height of 55 m. Compared to the previous study, here we inspect the larger dataset. In addition, apart from the vertical profiles of vertical momentum flux and kinematic heat flux, here we also investigate vertical profiles of some other turbulence variables.

We examined the influence of mesoscale flow on the elevated O3 concentrations recorded during 13-19 August 2000 in the coastal town of Rijeka (45.33°N, 14.45°E). Although high levels of ozone concentration are often observed there, this episode was unique due to hourly afternoon concentrations persistently higher than 180 μg m-3 and nocturnal levels above 100 μg m-3. To study this episode, available meteorological and ozone measurements were analyzed along with supplemental numerical simulations and trajectories. The measurements revealed favorable atmospheric conditions for the production of ozone, i.e., high air temperatures associated with (i) the exchange of two dominant (although relatively weak) large-scale flows: southwesterly versus northeasterly bora winds, and (ii) local thermal circulation. The bora wind was relatively weak and short lasting. Although the bora transported away the polluted air mass along the western Adriatic coast, the southwesterly flow returned ozone rich air toward the Alps, thus contributing to the overall pollution over the northern Adriatic Sea. Models revealed the superposition of the southwesterly wind and local, thermally induced winds that caused the regional transport of ozone toward the Alps and the eastern Adriatic coast. However, while the regional transport of ozone from the northern Adriatic was found to somewhat enhance the ozone concentrations in Rijeka (at the end of period studied), its surrounding local emission sources, uniform local thermal circulation systems, and recirculation of pollutants were crucial factors in the formation of the large daytime and nighttime ozone levels observed in Rijeka.

The levels of 1-min mean ambient particles with an aerodynamic diameter up to 1 μm (PM1) recorded at two nearby measuring sites in a residential area of Zagreb, Croatia, were analyzed with respect to the meteorological conditions (air pressure, horizontal and vertical wind speed, wind direction, global radiation, air temperature and relative humidity) and local traffic. PM1 mass concentrations were measured using a Model 8520 DUSTTRAKTM Aerosol Monitor (TSI Inc., Shoreview, MN, USA). One measuring site was placed next to a road with weak to moderate traffic, and the other was on a roof terrace approximately 100 m east of that road ; the heights of the aerosol monitor inlet were at 1.7 m (road) and 15.8 m (roof) above the ground level (AGL). Both road and the roof experiments were performed by the same instrument, and thus, they correspond to different time intervals. The roof results show that nearby roads do not affect the PM1 concentrations at the site 100 m from the road, while, according to preliminary road results, the effects of the local traffic appear only if more than 22 vehicles per minute pass by the instrument. However, PM1 levels seem to be strongly affected by traffic occurring in the more distant areas of Zagreb. Additionally, the results for certain wind directions also exhibit the influence of the regional and/or long- range transport of pollution on PM1 levels. Finally, it is shown that 1-min mean PM1 mass concentrations depend on the 1-min mean meteorological variables investigated.

Evaluation of turbulent fluxes in the surface layer is important for characterization of the atmospheric boundary layer (ABL). The turbulent heat flux in the surface layer is significant for the surface energy balance, while momentum turbulent flux is responsible for production of turbulence in stably stratified boundary layer. Additionally, turbulence, and specifically, turbulent fluxes strongly affect the fate of pollutants in the boundary layer. In order to investigate turbulent characteristics, it is necessary to separate turbulent perturbations from the mean flow. Turbulent and synoptic scales are typically separated by the spectral energy gap, which is often found at the mesoscale. Here we focus on nighttime conditions, which are generally favorable for the establishment of pollution episodes. In order to determine turbulent quantities from fine-resolution wind measurements, it is necessary to assess averaging time appropriate for the turbulent timescales. Therefore, here we also address to the problem of proper selection of averaging time interval.Wind data were measured by five ultrasonic anemometers with a sampling frequency of 20 Hz. Anemometers were placed at five heights, namely, 20, 32, 40, 55 and 62 m above the ground. The meteorological mast is located in a suburban, industrial area of Kutina, Croatia. The mast is above the grassy surface, and it is surrounded by approximately 20 m high trees, where the closest trees are about 20 – 30 meters distant.Lengths of averaging interval are determined by two methods based on Fourier analysis. The first method takes the length of interval as an inverse of frequency at which a minimum in the velocity spectrum is found. The second method (ogive) uses cumulative integral of cospectrum of perturbances of any two turbulent quantities. Here we employ perturbations of wind components and/or sonic temperatures. Afterwards, the averaging interval is taken as a value at which ogive converges to a constant. The time series of 5-min vertical momentum flux shows decreasing values with height up to 55 m where it starts to increase. At two uppermost levels in the nighttime period between 20 and 2 LST upward directed momentum flux exists. Kinematic heat flux has large values which decrease with height up to 55 m where it has a local maximal value.

Estimation of turbulent kinetic energy (TKE) is very important for atmospheric numerical modeling, since turbulent mixing is often parameterized using TKE. Additionally, turbulence characteristics and consequently, TKE strongly affects distribution of pollutants in atmospheric boundary layer. Thus, it is important to know how TKE is produced, transported and dissipated. Especially, for the stable boundary layer (SBL) it is needed to understand how these processes take place with respect to stability regimes ranging from weak to strong, and at different heights above the surface. In this study we investigate vertical profiles of TKE in the suburban, ground- based layer above the industrial quarter of town Kutina, Croatia during the nighttime, stable conditions. Such situations are generally characterized with intermittent turbulence and conditions favorable for the establishment of pollution episodes. Three-dimensional wind and sonic temperature were measured at five levels (20, 32, 40, 55 and 62 m above the ground) with the sampling frequency of 20 Hz. Measurements were done by WindMaster ultrasonic anemometers (Gill Instruments). Anemometers were mounted at the 62 m high mast located above the grassy surface. The mast is surrounded by up to about 20 m high trees. The closest trees are found at approximately 20 to 30 m far from the mast. In order to calculate turbulent quantities it is necessary to select appropriate averaging time interval, over which decomposition into instantaneous mean and random components can be done. In order to do that, two methods were deployed, both based on the Fourier analysis. The first method assumes existence of the energy spectral gap, which is typically found at the mesoscale. The averaging time is taken as the inverse of frequency at which the minimum in the velocity spectrum is found. The second method, which is somewhat subjective, employs the cumulative integral of cospectrum (ogive) of the vertical turbulent momentum flux. The averaging interval is defined as the inverse of frequency at which ogive converges to a constant value. Based on selected averaging time interval, following turbulent quantities were calculated: TKE, turbulent fluxes of momentum and heat, vertical fluxes of TKE, turbulence dissipation, and vertical profiles of above quantities.

Atmospheric boundary layer motions are statistically non-stationary, and therefore, it is necessary to transform them into statistically stationary (statistical properties do not change in time) time series. This transformation is performed by the mean removal process, which defines an integral time scale for turbulent fluctuations. The present study compares two methods for estimating physically relevant time scale in a stable, wintertime nocturnal boundary layer. This time scale is used to remove the unsteady mean component of the instantaneous time signal for any meteorological variable. In this way, turbulent fluxes that appear statistically stationary can be yield. The first method employs the Fourier analysis in order to remove the contamination by mesoscale motions in calculation of eddy correlation flux. The second method used for determining a relevant turbulence avenging time scale represents a cumulative integral of the kinematic heat flux or momentum flux cospectrum: the ogive method. The time scale is evaluated using three-dimensional sonic anemometry data acquired at five levels of a meteorological mast (20, 32, 40, 55 and 62 m a.g.l.) located in the industrial part of Kutina, a town in Croatia. The results indicate the existence of the spectral gap scale in the spectrum of streamwise velocity component at all levels except at 32 m. This gap scale can be found for periods between 30 and 7 min for 20 m level and between 22 and 7 min at other levels. The time scale estimated by the second method is based on the location of the local maximum value of the 2 ogive function of the kinematic heat flux and momentum flux cospectra. The ogive method gives time scales that define the high-frequency end of the spectral gap.

The Sahara is the world’s largest source of the aeolian desert dust. The dust can be entrained over large areas in dust storms, transported over thousands of kilometers and then deposited downwind. Saharan dust has a major influence on soil characteristics, oceanic productivity, air chemistry and climate. Most Saharan dust is deposited from the atmosphere over Mediterranean countries of southern Europe by dry or wet deposition. Here, the characteristics of Saharan dust episodes over part of the southern Europe (Croatia) will be shown. We tried to determine the frequency of mud rains over Croatia and investigated their influence on precipitation chemistry. Further on, we analyzed the influence of Saharan dust on the coarse fraction levels (PM10) at several measurement sites in Croatia. Saharan dust episodes were identified using satellite data and backward trajectories. In addition, synoptic situations prevailing during the investigated Saharan episodes were analyzed. Three main types of weather situations connected to the transport of the dust from Sahara desert to Croatia were revealed and their characteristics will be shown.

Mass concentrations of the airborne particulate matter with the aerodynamic diameter less than 1m (PM1.0) were measured at the residential part of Zagreb during the period from 14 September to 6 October 2011. Measurements were performed by the DUSTTRAKTM Aerosol Monitor at the temporal resolution of one minute. The monitor was mounted at the 3 m high mast located at the roof terrace of Geophysical Institute building at Horvatovac, with the inlet height at 15.8 m above the ground. At the same site 1-min means of the air pressure, temperature, wind speed and direction and relative humidity were also recorded. Diurnal variation of PM1.0 concentrations went along with the diurnal variation in human activities, and particularly in the traffic. Investigation of the relationships between the PM1.0 concentrations and ambient meteorological conditions suggests the importance of advection of pollution towards residential environment. Finally, results show the dependence of PM1.0 levels on relative humidity.

The article is a short review on the occasion of the 150th anniversary of Geophysical Institute in Zagreb.

NATO Advanced Research Workshop: Climate Change, Human Health and National Security ; Dubrovnik, Croatia, 28–30 April 2011 ; Climate change has been identified as one of the most serious threats to humanity. It not only causes sea level rise, drought, crop failure, vector-borne diseases, extreme events, degradation of water and air quality, heat waves, and other phenomena, but it is also a threat multiplier wherein concatenation of multiple events may lead to frequent human catastrophes and intranational and international conflicts. In particular, urban areas may bear the brunt of climate change because of the amplification of climate effects that cascade down from global to urban scales, but current modeling and downscaling capabilities are unable to predict these effects with confidence. These were the main conclusions of a NATO Advanced Research Workshop (ARW) sponsored by the NATO Science for Peace and Security program. Thirty-two invitees from 17 counties, including leading modelers ; natural, political, and social scientists ; engineers ; politicians ; military experts ; urban planners ; industry analysts ; epidemiologists ; and health care professionals, parsed the topic on a common platform.

Lengths of averaging intervals applicable for investigation of intermitted turbulence during the nighttime stable, wintertime conditions are determined by two methods, both based on Fourier analysis. Wind data were measured by five ultrasonic anemometers with a sampling frequency of 5 Hz. Anemometers were placed at a mast located in a suburban, industrial area of Kutina, Croatia. Corresponding measurement heights were 20, 32, 40, 55 and 62 m above the ground, respectively. The mast is located above the grassy surface, surrounded by approximately 20 m high trees. The closest trees are about 20 – 30 meters far from the mast. The first method for determination of the length of the averaging interval is based on a cummulative integral of cospectrum of perturbances ogive) of the wind speed component and sonic temperature. The averaging interval is taken as a value at which ogive converges to a constant value. Second method assumes the length of averaging interval as an inverse of frequency at which a minimum in the velocity spectrum occurs. Variations of the lengths of averaging intervals with the height obtained by both methods are inspected and the differences between results obtained by the two methods are discussed.

In this paper, the hourly mean ambient concentrations of nitrogen dioxide (NO2), carbon monoxide (CO), hydrogen sulfide (H2S), sulfur dioxide (SO2), ozone (O3), benzene (C6H6) and particulate matter (PM10) measured over the last 4.5 years at the two urban sites in Rijeka are analyzed. The first site is located in the center of the town, whereas the other is located in the southeastern part, closer to the industrial zone of Rijeka. The site in the center of Rijeka is subject to heavy vehicular traffic, thus exhibiting substantially higher NO2, CO and PM10 concentrations ; however, the other site is characterized by much higher SO2 concentration. The diurnal and annual variations in pollutant concentrations reflect the effects of both human activity and periodic variations in meteorological conditions, whereas average weekly variations differ as per the anthropogenic emissions. Finally, in accordance with the trend of decreasing pollutant concentrations since the mid-1980s, SO2 concentrations decreased at both the sites, whereas NO2 concentration decreased at the site closer to the industrial area of Rijeka.

The aim of this research was to examine Saharan dust transport over the Mediterranean towards Croatia. We analyzed several episodes of mud rain events during the period 2001-2005 on two mountainous, background sites. The mud rain events related to Saharan dust outbreaks were identified using Earth Probe/Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) data and backwards trajectories. The mud rains were characterized by higher calcium concentrations and pH values. In addition, we investigated the contribution of mud rains to the annual total calcium deposition.

Airborne particulate matter (PM) comprises dust, dirt soot, smoke, and liquid droplets suspended in the atmosphere. Particle sizes and their physical and chemical characteristics are determined by the formation processes and subsequent reactions in the atmosphere. Typically, urban aerosol can be divided into two main fractions ; fine (with diameter less than 2  m) and coarse particles (diameter of more than 2  m). Fine particles mainly originate from combustion, and, they comprise sulfates, organic ammonium, nitrates, carbon, lead, and some trace constituents. Coarse fraction is produced by mechanical processes, and it contains crustal material (i.e. silicon compounds, iron, aluminum), sea salt and plant particles. There are number of studies addressing to particles with diameter less than 10 and 2.5  m (PM10 and PM2.5, respectively), compared to relatively sparse literature on PM PM1.0 (particles smaller than 1.0  m in aerodynamic diameter). The aim of the study was to assess pedestrian’ s exposure to the PM1.0 fractions in a residential part of Zagreb, Croatia under various traffic density conditions. Continuous PM1.0 concentrations were measured using Model 8520 DUSTTRAKTM Aerosol Monitor (TSI Inc., Shoreview, MN, USA). The instrument is portable, and provides the real-time data at the temporal resolution of 1 s. In order to assess pedestrians’ exposure, the DUSTTRAKTM was placed at the sidewalk of a road, at the height of 1.7 m above the ground, half meter away from the road edge and with the inlet perpendicular to the roadway. The road has two lanes of opposite direction, separated by the centerline. The traffic is generally low-speed (up to 50 km / h), and its density varies from low to moderate (at the most up to about 30 vehicles per minute). Measurements of PM1.0 concentration at the resolution of 1 s were performed during ten time intervals of 45 min. Simultaneously, meteorological data (air pressure, air temperature, horizontal and vertical wind, global radiation and relative humidity were recorded by automatic meteorological station META 2000 (AMES, Brezovica, Slovenia) approximately 50 m far from the road at the temporal resolution of 1 min. Measured PM1.0 concentrations at 1 s resolution varied from 4 to 413  g m-3, and they were on the average 38.8  g m-3. Investigation of relationships between the PM1.0 levels and various meteorological parameters and traffic density revealed the strongest correlation of PM1.0 concentrations with relative humidity and wind direction, where the latter suggest the importance of distant pollution sources. While wind speed and traffic density affect the concentrations of the ambient fine particles, temperature and global radiation do not seem to influence the PM1.0 levels.

In this study, a time series from the ground level ozone monitoring station for Rijeka (Croatia) as well as the associated meteorological conditions were investigated. In the summer, during 13 to 19 August 2000, the afternoon hourly ozone measurements were consistently higher than the 180 μ g m-3 which represents an information threshold of pollutant concentrations according to the national standards. During the night the ozone concentrations were unusually very high as well, above 100 μ g m-3. An analysis of the observations was performed to identify characteristics of the low-level wind in the Rijeka Bay and the results of a nonhydrostatic mesoscale meteorological model WRF were compared with the observations with respect to these characteristics. The contribution of the distant pollution sources to observed concentrations was evaluated by the atmospheric chemical model EMEP.

Stable atmospheric conditions are often connected with the occurrence of high pollution episodes especially in urban or industrial areas. In this work we investigate a severe SO2 episode observed on 3– 5 February 2002 in a coastal industrial town of Rijeka, Croatia, where very high daily mean concentrations (up to 353.5μ gm− 3) were measured. The episode occurred under high air pressure conditions, which were accompanied with a fog and low wind speeds. Three air quality models (50-km EMEP model, 10-km EMEP4HR model and 1-km CAMx model) were used to simulate SO2 concentrations fields and to evaluate the relative contribution of distant and local pollution sources to observed concentrations. Results suggest that the episode was caused predominately by local sources. Furthermore, using three-dimensional, higher-order turbulence closure mesoscale meteorological model (WRF), the wind regimes and thermo-dynamical structure of the lower troposphere above the greater Rijeka area (GRA) were examined in detail. Modelled atmospheric fields suggest several factors whose simultaneous acting was responsible for elevated SO2 concentrations. Established small scale wind directions supported the transport of air from nearby industrial areas with major pollution sources towards Rijeka. This transport was associated with strong, ground-based temperature inversion and correspondingly, very low mixing layer (at most up to about 140m). Additionally, the surface winds in Rijeka were light or almost calm thus, preventing ventilation of polluted air. Finally, a vertical circulation cell formed between the mainland and a nearby island, supported the air subsidence and the increase of static stability.

In this work we analyzed one mud rain episode, with the highest TOMS (Total Ozone Mapping Spectrometer) aerosol index over Croatia during the period 2001-2005. This episode was connected with strong Saharan dust outbreak which occurred over Mediterranean Sea from 8th to 14th April 2002. The synoptic situation over Croatia was analyzed for the episode, as well as AI images, backwards trajectories and precipitation chemistry.

Achievements of regional application of the Unified EMEP model for Croatia – EMEP4HR is presented. A model suite for the purpose of regional air quality assessment in Croatia is created together with Croatian emission inventories at 10km resolution. This suite is to become operational model suite for the air quality purposes in Croatia. Results of methodology development for allocation of emissions in fine scale, complemented with the compilation of activity data and emission data from local and national authorities are presented. Input data sources and data preparation procedures are presented and discussed. A Meteorological pre-processor has been developed in order to use ALADIN Numerical Weather Prediction (NWP) model, as a meteorological driver at 10 km resolution. Development of the physical and dynamical schemes of the Unified EMEP model, made in the framework of EMEP4HR, as well as smaller scale applications, are mentioned. Model results are shown and basic verification on measured data is performed. Special focus is put on the differences in the model performance due to ALADIN and HIRLAM meteorological drivers on 10 km resolution.

U tekstu je dano izvješće o radionici 'Air quality management, monitoring, modeling, and effects' koja je pod pokroviteljstvom EURASAP organizacije održana u Geofizičkom odsjeku.

A severe pollution episode occurred in Rijeka, Croatia during 3-5 February 2002, where a daily mean SO2 concentration reached even 225.5 μ g m-3. A previous study of the above episode suggested the fumigation due to the weak synoptic circulation and high-pressure conditions. Rijeka is a coastal industrial town surrounded by mountains, located at the Northern Adriatic, at a position where the sea has made its deepest incision into the European continent. Thus, it exibits very complex wind regime, which can affect the air quality. The aim of this study is to investigate mesoscale atmospheric conditions, and particularly airflow and turbulence within the lower troposphere during above severe pollution episode. The results were produced using 3-D, higher-order turbulence closure model and will help in the future rational design of integrated emissions control strategies for the greater Rijeka area.

We investigated an unusual elevated-ozone episode that took place at a high altitude measuring site Zavižan (44.817°N, 14.983°E, 1594 m a.s.l.). The episode was characterized by three consecutive peaks. The first one was the highest (over 120 ppbv), and it occurred at the late night on 17 July. Following two (both about 110 ppbv) appeared approximately 18 and 36 hours after the first peak, respectively. The night-time maximum and the departure from the usual diurnal variation of ozone concentration during investigated episode point to the non-local pollution sources, rather than to local photochemical production. Thus, recorded ozone peaks might arise due to the long-range transport of photo-oxidants ; 2) stratospheric ozone intrusion ; or 3) they might be result of both (1) and (2). In order to inspect which of above processes is responsible for the increased ozone concentrations we applied the unified EMEP model, which among others, simulates atmospheric transport and deposition of photo-oxidants, and, a mesoscale numerical weather prediction model WRF-ARW V2.2. Additionally, the larger scale atmospheric conditions were examined based on the ECMWF ERA-40 reanalysis fields. Results suggest that the stratospheric ozone intrusion played an important role in the occurrence of investigated episode.

The interplay of the synoptically forced southeastward Etesian winds with the small scale, thermally induced sea-land breezes over the Adriatic is investigated. In the study both measured and modeled surface air temperature and wind data were analyzed. Measuring sites were selected in order to cover northern, eastern and western Adriatic coast, as well as one offshore and one open-sea location. Modeled fields were obtained from operational hydrostatic mesoscale meteorological model ALADIN at horizontal resolution of 8 km. In addition, modeled wind fields were dynamically adapted to the resolution of 2 km. It is shown that model at the operational horizontal resolution of 8 km reasonably well reproduces surface airflow over the Adriatic. The finer horizontal resolution resulted in the similar wind fields, except for occasional, somewhat stronger winds that were found downstream of topographically complex regions along the eastern coast. The air temperature was not well reproduced for the open-sea site (Palagruža) and the coastal site (Brindisi), which is compared to the other coastal sites, due to its specific location, more exposed to the effects of entire Mediteranean Sea. Results also revealed salient differences in airflow above the eastern and western Adriatic, which are due to different topographical setups of the two coasts. Above the eastern and western Adriatic, the domination of the sea-land breezes and the Etesians is found, respectively. Along the eastern coast, the sea-land breezes are additionally enhanced due to additional topographical forcing and channeling effects, while along the western coast they are weaker and mainly pushed inland. Results also suggest several outstanding, region-specific airflow features that are likely to be typical for the investigated synoptic setup. During the daytime, these are: 1) the pronounced divergence above the northern Adriatic ; 2) very strong winds west of Montenegrin and Albanian coast ; and 3) enhanced winds above the central portion of the eastern coastal area. For the nighttime typical are 4) the topographically induced jets along the eastern coast, while entire day is characterized by 5) elevated wind speeds adjacent to Gargano peninsula. Both, the differences between the eastern and western Adriatic and, the occurrence of the above region-specific features can be attributed to topographical diversities and consequent effects of slope flows and airflow channeling.

Operational oceanography of the Mediterranean Sea has received significant attention in recent years. The Adriatic Sea in particular is covered by a regional hydrodinamical model and several shelf models, where the necessary boundary conditions are prescribed by simple one-way nesting between respective models. The atmospheric forcing has been taken from the global ECMWF model having 0.5 degrees longitude and latitude resolution. Differences between meteorological fields over the Adriatic Sea as predicted by the regional meteorological model ALADIN and the global ECMWF model are analyzed. The focus is on the sirocco episodes between November 2002 and September 2003. Results indicate that the orography, namely Gargano Mountains and Apennines, has a significant effect on the sirocco airflow. It is shown that the Gargano Mountains induce the typical structure of the flow past the 3D obstacle in the lee that influences the wind-curl field. While the ALADIN model resolves the structure, the coarser ECMWF model is unable to do so. Consequently, different atmospheric forcing may result in different impact of the sirocco wind on the Western Adriatic Current.

An overview of the pollutant transport and dispersion modeling activities performed in Croatia is given. These includes a modeling of the long-range transport of pollutants by means of the Lagrangian box-model, mesoscale modeling (coupling of the MM5 and CAMx model) and experimental studies aiming to establish the relationship between the traffic density and mobile sources emissions.

Prikazuje se pregled nekih od dosadašnjih saznanja o utjecaju vremena i klime na ljudski organizam.

Enhanced sea level oscillations with devastating effects occurred on 26/27 June 2003 in the east Adriatic. The phenomenon was recognized as a resonantly coupled air-sea interaction, where the Proudman resonance occurs between the propagating atmospheric pressure disturbance and the open-sea wave. Afterwards the harbor resonance occurs between the propagating air-sea disturbance and the internal harbor oscillation. The time scale of the atmospheric pressure disturbance was 2 – 3 hours with the phase speed of ~ 22 m/s, and its maximum amplitude reached 8 hPa. This study examines the dynamics and predictability of the atmospheric component of the coupled system using the MM5 numerical model. First, the initiation, amplification and maintenance of the system are examined. The perturbation originates in the Alpine region, where the potentially unstable air in the westerly current lifts over the Alps resulting in convection and wave development. The wave and convective activity apparently couple in a wave-CISK manner and propagate southeastward down the eastern Adriatic coast. The potentially unstable air above the Adriatic additionally amplifies the system along its track. The dissipation of the system occurs after the landfall after about 12 hours of the Mesoscale Convective System (MCS) lifetime. Second, the performance of the numerical model at the resolution that is similar to operational NWP model resolution is examined. This severe event is highly susceptible to the details of the model configuration, presumably due to the sensitivity in coupling of the wave and MCS. Thus, although the model is able to reproduce and forecast this kind of event at a fairly coarse resolution, the details of the spatial structure, as well as the time of onset, are questionable. In this case, the greatest sensitivity is primarily in the treatment of moist and convective processes.

During the warm part of the year, the etesian winds blow over the Mediterranean. They are more pronounced over its eastern parts. Etesians are dynamically generated by joint influence of the deep Asiatic low (Karachi depression), and the high pressure system of the Azores. Over the Adriatic, the etesians are rather weak. Thus, corresponding southeastward air flow is clearly seen only at distant islands, while along the coast it is dominated by the local, thermally induced sea-land breezes (SLB). Local SLB are caused by the different thermal properties of the land and the sea. Along the eastern Adriatic, the irregularly shaped coast with a number of islands, islets, cliffs and adjacent Dinaric Alps causes a complex wind regime which is a result of the interaction of the SLB induced by both mainland and islands and slope winds. The level of the SLB regime complexity differs from one locality to another, depending on the complexity of the local topographical and surface conditions. Here, we discuss the airflow characteristics at the three measuring sites during the periods favorable for the establishment of both, etesians and SLB. The measuring sites are selected so as to capture gradual changes from coastal to open-sea conditions. Partuclar attention is given to the airflow at the offshore site (Komiža) which differs substaintialy from the coastal (Split) and open-sea (Palagruža) wind regimes.

High resolution meteorological fields over the Adriatic derived from mesoscale ALADIN/HR model for the Nov/2002 - Sep/2003 period are compared with corresponding low resolution fields obtained from global ECMWF model. The analysis is performed on mean values calculated over strong bora and strong sirocco episodes. It is shown that not only bora but also the sirocco-type weather is largely influenced by local orography. The results suggest that use of mesoscale meteorological forcing can significantly improve oceanographic forecasting in the Adriatic.

This study investigates the influence of weather types found over the continental part of Croatia on daily PM10 concentrations and concentrations of metallic compounds in PM10 (namely manganese, lead and cadmium) in air during 2000-2002 period. Pollutant concentrations were measured at the northern, residential part of Zagreb, far from the major pollution sources. Weather types were determined from synoptic charts. In the employed categorization six different patterns were recognized: radiation weather type, high pressure ridge, precipitation weather type, southeastern advection, northeastern advection and wind weather type. The most frequently, elevated concentrations were related to radiation weather type and southeastern advection, while the lowest concentrations were recorded during the wind weather type. Obtained results generally suggest a major role of the local pollution sources, and particularly of the Zagreb industrial zone, in suspended particles/metallic compounds pollution. Since cadmium exhibits somewhat different behavior, the role of the long-range transport in cadmium pollution needs to be further investigated. Synoptic conditions favorable for elevated concentrations occurred in about 37 % of investigated days. Typically, these conditions are characterized by 1) the weak winds and turbulence, and consequently, inefficient pollutant concentration dilution (the nighttime and wintertime radiative conditions) ; or 2) southeastern airflow (southeastern advection and daytime radiative conditions), which transports pollutants from industrial zone of Zagreb towards the measuring site. Due to the latter, particulate pollutants emitted in the industrial zone pass rather frequently above the eastern part of Zagreb.