Project hypotheses are 1.) The effect of relatively warm sea aids the bora front propagation out over the sea more than to the bora strength. The bora front gets more distorted over the warm than over the cold sea. Secondary nonlocal effects due to the Earth rotation also occur. 2.) Highest frequencies associated to bora, roughly ~0.01Hz to 1Hz , are of a local type, while lower frequencies, related to bora pulsations, ~0.001Hz to 0.01Hz, are of a nonlocal origin. 3.) Numerical predictions for yugo wind (similar to sirocco) speed is often too high compared to near-surface measurements. This probably means that either the roughness length is too small in the model, or the modeled surface temperature is wrong. Either way, the surface parameterization should be improved for yugo airflows. 4.) Katabatic and anabatic flow, i.e., down- & up-hill typically during nighttime & daytime respectively, can be parameterized in those models having inadequate resolution to resolve such small circulations; The latter may have important cumulative effect on mesoscale air transport & dispersion, air quality & micro-climate. We already have analytic models based on which such a parameterization can be based upon including variable eddy diffusivity K(z) and Coriolis parameter. We want to also check these simple analytic kata-& anabatic models against more measurements with high sampling rates. 5) Quasi-horizontal diffusion & turbulence is poorly understood today, especially under very stable stratification; new observation techniques seem to be lacking. In the other hand, we try to use fractional PDE to emulate some anomalous turbulent processes. In basically all the hypotheses listed above, we deal with intrinsic orographic circulations driven by terrain or surface temperature differences.


BORA project has been the most productive scientific project of the Ministry of Science, Education & Sports in geosciences for 2007 throughout the whole project, i.e., the end of 2012.




-The main goal is to better understand and explain quantitatively some of the basic meso- and microscale processes occuring at coasts and mountains (e.g. three-dimensionality, unsteadiness and turbulence of the bora, scirocco, valley & mountain circulations). Only in this way, it will be possible to forecast the local weather phenomena more reliably, and to understand and project future local micro-climate variations.

-Our overall goal relates to parameterizations improvements in numerical weather-forecasting models. (Processes that cannot be resolved explicitly in the models should be parameterized. Since the models typically use horizontal & vertical resolution of (dx,dz)~(10km,500m), they intrinsically cannot "see" short waves, turbulence, clouds, fog, i.e. micro-physical processes of condensation, evaporation, etc.). Our goals make a direct basic scientific support to applied research at the Weather Service, see




Maja Telišman-Prtenjak, Željka Fuchs, Inga Lisac, Tomislav Marić, Željko Večenaj, Antun Marki, Damir Počakal, Mladen Viher, Vladis Vujnović, Thorsten Mauritsen, Leif Enger, Stefan Soderberg, Dale Durran, Larry Mahrt, Nedjeljka Žagar, Mark Žagar.




Iva Kavčič, Siniša Miličić, Tomi Haramina, Marko Pavić, Amela Jeričević, Lukša Kraljević, Danijel Belušić, David Raymond, Patrick Samuelsson.




With a better perception of wave-turbulence interactions in the atmosphere over the complex terrain, we will strenghten mesoscale theory; therefore, we will efficiently improve forecasts of the prognostic weather models today. Moreover, developing the theory and providing the model improvements, we would choose the observational sites for future experiments more objectively, as well as the observational areas, periods and durations for intensive field experiments.




Although firstly of a theoretical & numerical modeling nature, the project has a number of applications. That can be divided into: short-, medium- and long-term applications. Examples for each follow.


(1) Improvement of the weather forecast over Croatia. With the better understanding of the local meteorological processes, we will improve their parameterizations in NWP models. Consequently, the models will better predict the local wind, temperature and humidity.


(2) Aiding better meteorological, climatological and ecological studies for road constructions, buildings, etc. For instance, we measure, analyze & calculate turbulent properties of bora wind, that is, the input (forcing) to new improved road shields against bora effects on the highways. Detailed recommendations for possible use of wind energy will be given. The basis for that is an in (1).


(3) Basis for strategic future projections of Croatian agroculture, hydro-culture, etc. for the next few decades. There are some indications that Croatia will become drier in average; details are unknown today. The project shall be a part of the basis for future studies of climate variations over and around Croatia; we contribute on micro-climate issues (other projects within the program will focus on the overall climate issue).


The largerst part of these applications will take place under a close collaboration and leadership of the Weather Service of Croatia. Stengthening the collaboration between our Faculty and the Weather Service is of crucial importance for the applications of the research proposed.




Wave-turbulence interactions in the atmosphere and their relations to other processes (radiation, condensation, evaporation, etc.) over complex terrain are not covered well by theory today. Real advancements in this field is slow since one deals with coupled nonlinear, unsteady 3D processes. Simultaneously, meso- & microscale phenomenological realizations grow rapidly due to ever better measurements and numerical simulations. Nonetheless, the results are difficult to interpret since there is no unifying mesoscale theory today.


The coast represents a stepwise change in the surface characteristics where the sea, air and complex terrain meet. At such locations various types of ABL and waves may occur. Very stable ABL and stratified turbulence interacting with short buoyancy waves still remain principally unsolved problems; these also may appear near coastlines, and we want to continue our research in this area too.


Integrated effects of the mentioned coastal and orographic circulations onto climate change are poorly understood today. These are probably of cumulative nature on micrometeorology if the effects themselves are mostly local. But if sources deposit their effects far away, i.e. nonlocal effects, maybe hypothesis of a microclimate type will have to be rejected. Some of the updated backbround may be found at




It is a surprising fact that today we know more about the dynamics of an atom than about the motion of a cubic meter of air or water. Weather & climate research must not be ignored today simply because the whole issue is way too important for nature and human survival. Our questions are simple & basic: why the weather & climate are as they are (only afterwards one may derive a consistent question of prognosis). In the core of this issue is wave-turbulence interaction (whose consequence is much intensified fluid mixing & transport).


We want to study mesoscale processes (between those directly sensed by humans and that readily seen in synoptic charts). Behind the scenary is a multi-scale essence of geophysical processes: energy cascade among planetary, synoptic (regional), meso- and microscale. Therefore, this belongs to basic research.


Our research & findings, although basic in its nature, is directly applicable in tourism, traffic, infra-structure, agro-culture, forestry, environmental protection, energetics, etc. That goes via natural inter-disciplinarity of geophysical processes.




We use all three main metods of geophysics in studying atmospheric wave-turbulence interactions: 1) measurements & observations, 2) analytical modeling, 3) numerical modeling (simulations). While integrating all the three approaches, we strengthen theory and recommend direct applications in various types of presentations (conferences, peer-reviewed papers, seminars, etc.).




While the main goal is to better understand meso- and microscale processes at the Adriatic coast & mountains (3D, unsteadiness & turbulence of sea-breeze, bora, scirocco, mountain & valley flows), the results will yield a more reliable forecasting of the local weather (timing, location, intensity, etc.), and to project the related microclimatic variations into future. We expect to publish several peer-reviewed scientific papers each year of the project.


The results will have a positive impact on new parameterizations in numerical prognostic models for weather, climate and air quality. With a deeper understanding of wave-turbulence atmospheric interations over complex terrain, the mesoscale theory strengthens; this is probably the most effective way to improve the forecast from the existing weather & climate models as the latter depends strongly on the parameterizations. Developing theory and consequently improving numerical models gives a sound basis for future climate projections and thus an overall development of the society. For example, one of the results will be a new parameterization of local circulations over the Adriatic area and inland; this will be recommended to the models used routinely for weather forecasting. Another result will be an estimation of the wind energy potential in the surface layer over eastern Adriatic area; this could yield commerical applications later on.