CONTINUOUS RECORDS OF NON-STANDARD RADIO WAVE REFRACTION IN ALPINE REGION

Recent deployment of two radar systems in Croatia renews interest for radio wave refraction research. The most cited work about "refractive climatology" is the Recommendation P.453-9 of the International Telecommunication Union-Radio Communication (ITU-R). Due to generalization of topics and global scale descriptions this Recommendation has no fine details on local scale. Moreover, statistical descriptions in the Recommendation lacks climatological approach and methodology of these, in fact, meteorological phenomena. Without proper climatological description we are unable to draw conclusions about atmospheric and local factors on radio wave refraction. The work is focused on non-standard refraction (subrefraction, superrefraction and radio ducts) patterns, not to models of refraction index because these models are well known and documented. Formula set used in this work is newer than those used in Recommendation. The new set was developed at the US Navy Office of Naval Research. Differences between these two sets are small (around 1% in absolute terms) so results are still comparable. Vertical profiles of the modified refraction index were computed from regular balloon radio-sounding data. Records are continuous, 4-7 years long for 12 aerological stations from Alpine region: Milano, Udine, San Pietro, Payerne, Muenchen, Hohenpeissenberg, Linz, Vienna, Innsbruck, Graz, Ljubljana and Zagreb. In the future, work will be extended to about 30 stations, all in range of the Croatian radar network.