The wind in Zagreb (A contribution to the knowledge of climate of the city of Zagreb, II)

(in Croatian)

Abstract

Presented are the surface airflow characteristics in Zagreb, based on five to fifteen year period of wind data. It is shown that the surface airflow is weakened in Zagreb and is conditioned by the city situation in the mountain lee side for prevailing general circulation. The local circulation system is developed nearby. General circulation, which is connected with synoptical disturbances, is modified in Zagreb and it appears in two main types according to the wind direction. They are the airflow coming from northeastern quadrant and the other coming from the western quadrant. The local circulation system is not strong, but it is persistent and can be recognise in almost all statistical results. The system is complex and consists of the slope wind, which is the most pronounced, and of the valley wind. Some urban influence on the local circulation is also found. The valley wind is less pronounced over the city area than over the surrounding terrain. The contribution of a particular circulation type to the entire airflow regime is strongly influenced by seasons. All the conclusions are documented by numerical data and graphically. The results are obtained by statistical analyses of wind roses, by resolving the empirical frequency distributions into Gauss normal distributions, and by spectral variance analyses of the hourly wind vector data