ENERGY BUDGET AT THE EXPERIMENTAL VINEYARD IN ZAGREB

Within the collaboration of VITiculture and CLImate Change in Croatia (VITCLIC) project and Croatian-Hungarian bilateral scientific program, micrometeorological measurements are performed at the Faculty of Agriculture experimental vineyard near Zagreb in the hilly experimental field during the vegetation periods of 2017/2018 and 2018/2019. The microclimate of two places of cordon cultivated grape has been studied for the investigation of the effect of cultivation method. In one row, the grapes were left to be naturally covered by leaves, while in the other row the leaves were being thinned corresponding to the cultivation method. For characterizing the microclimate, the relative humidity and air temperature, wind speed and direction, UV radiation, leaf wetness and leaf temperature were measured inside the cordon rows among the leaves. Air temperature, relative humidity and wind speed gradient have also been measured above the plants. Radiation budget components were detected with CNR1 net radiometer. Heat flux into the soil and the soil temperature and moisture profiles from the surface to a depth of 1 m were also determined. Two soil heat flux plates were set at 8 cm deep. Measurement frequency was 5 sec and the average time was 1 min using Campbell data collecting systems. Our goal, besides the agroclimatological investigations, is the estimation of soil and surface energy budget components (using Bowen-ratio and gradient methods) and the determination of the optimum roughness length and displacement height as a function of the wind velocity. Daily variation of meteorological elements and energy budget components are demonstrated with case studies

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

The exchange of heat, momentum, and mass in the atmosphere over mountainous terrain is controlled by synoptic-scale dynamics, thermally driven mesoscale circulations, and turbulence. This article reviews the key challenges relevant to the understanding of exchange processes in the mountain boundary layer and outlines possible research priorities for the future. The review describes the limitations of the experimental study of turbulent exchange over complex terrain, the impact of slope and valley breezes on the structure of the convective boundary layer, and the role of intermittent mixing and wave–turbulence interaction in the stable boundary layer. The interplay between exchange processes at different spatial scales is discussed in depth, emphasizing the role of elevated and ground-based stable layers in controlling multi-scale interactions in the atmosphere over and near mountains. Implications of the current understanding of exchange processes over mountains towards the improvement of numerical weather prediction and climate models are discussed, considering in particular the representation of surface boundary conditions, the parameterization of sub-grid-scal

Micro-Scale Properties of Different Bora Types

In this paper we use 20 Hz wind measurements on three levels (2, 5, and 10 m) to investigate the differences in micro-scale properties of different bora types, i.e., deep and shallow bora with further subdivision to cyclonic and anticyclonic bora cases. Using Fourier spectral analysis, we investigate a suitable turbulence averaging scale and bora gust pulsations. The obtained data set is further used to test the Monin–Obukhov similarity theory, the surface layer stratification, the behavior of the terms in the prognostic turbulence kinetic energy equation, and the wind profiles. One of our main goals is to identify possible micro-scale differences between shallow and deep bora types because of the possible different mountain wave dynamics in those flows. We found that a turbulence averaging scale of 30 min is suitable for this location and is in agreement with previous bora studies. The wind speed power spectral densities of all selected bora episodes showed pulsations with periods of 2–8 min. This suggests that mountain wave breaking was present in all cases, regardless of flow depth and synoptic type. The stability parameter analysis confirmed the near-neutral thermal stratification of bora; a consequence of intensive mechanical mixing. No significant differences related to bora type were observed in other micro-scale parameters