HIGH RESOLUTION SIMULATION OF A SEVERE BURA EVENT USING NONHYDROSTATIC NUMERICAL MODEL

Bura is strong and gusty wind common for the eastern Adriatic coast, with the most severe events beneath southern part of Velebit mountain. Due to traffic significance of the area and the fact that bura has strong impact on traffic, it is necessary to forecast the bura speed, onset and duration. A mesoscale nonhydrostatic numerical weather prediction model MM5 is employed in order to test and verify the model capabilities of forecasting wind speeds and spatial variabilities on very fine domain resolution of 1 km. During the winter 2003-2004 several bura events were recorded. The longest bura event, taking place from 22-25 December 2003 is analyzed. The model results are compared with the measured data taken from four automatic stations located on different altitudes along the slopes of Velebit. It is found that the model is able to predict onset duration and end of a bura episode with a reasonable accuracy. It is also found that the model is able to reproduce small scale bura variability

THE IMPACT OF MODEL RESOLUTION ON SIMULATED DISTRIBUTION OF BURA

Nonhydrostatic mesoscale model MM5 was used in order to model a spatial distribution of bura wind in Maslenica bridge region (Croatia). A 3 km domain and a 1 km domain nested in a 3 km horizontal domain were used. Both runs were initialized from the same NWP ALADIN/Hr runs. Spatial differences between the model setups are addresed. The main characteristics of wind field was well indicated on both domains. It is found that 1 km domain much better reproduces local characteristics of wind field than 3 km domain

METEOROLOGICAL CHARACTERISTICS OF A SNOW PIT IN GORSKI KOTAR REGION (CROATIA)

This paper outlines the first meteorological measurements taken from a snow pit in the Gorski kotar region, which is located in the mountainous western part of Croatia. The aim of the research was to determine the main meteorological characteristics of the location. The research rested on the assumption that meteorological conditions in snow pits could be indicators of regional climate change. Temperature and relative humidity were measured inside and in the vicinity of the snow pit. Two samples from different depths of snow accumulated at the bottom of the pit were collected for analysis. Changes in temperature and relative humidity in the vicinity of the snow pit showed typical seasonal variations. The values inside the pit were constant. The pH measurements of the snow samples showed no indication of an increased acidity of snowmelt at the monitoring location. Further research in some other snow pits should be conducted in order to test the general relevance of the obtained results

PREDICTION OF STABILITY AND MIXING HEIGHT IN THE COMPLEX OROGRAPHY

The aim of this study is to investigate the possibilities of using the numerical weather prediction (NWP) model ALADIN to calculate input parameters, stability and mixing height (MH), for the Gaussian dispersion model. Since dispersion parameters were not a part of the routine model output, the methods for their calculation were tested. The model characteristics were analysed on the complex orography of the Rijeka area, the most developed industrial part of the Croatian coast. This was also done for the episode of elevated SO2 concentrations due to fumigation processes. It was shown that the ALADIN model could be used for calculations of the dispersion parameters. The model unreliability in2 m temperature prediction relates to days with fog or mizzle and there is also an indication of night-time 2 m temperature underestimation