Climate trends and variability of rain rate derived from long-term measurements in Norway



Radio systems are affected by rainfall, and the attenuation increases significantly with rain rate and frequency. Above about 10 GHz rainfall must generally be considered for estimating expected link availability with sufficient attenuation margin included. Rain rate is a key factor, and depending on climate, it will dictate the possible path length and other factors such as antenna size, for the planned performance of a system that operates at higher frequencies than about 10 GHz. This paper presents results from an analysis of Norwegian tipping bucket rain gauge data from 1967 to 2013. It is found that the rain rate currently used by the Radiocommunication Sector of the International Telecommunication Union recommendation for attenuation prediction, R0.01—the rate exceeded for 0.01% of an average year—has actually increased in all parts of the country from where long-term data exist. Moreover, the year to year variability is significant. The increase may well be seen as a consequence of climate change. Such a change may cause higher attenuation effects than expected when radio links are designed following “normal” dimensioning procedures.