Average radio refractive index lapse rate of the lower troposphere for locations in NW Europe

In order to plan radio communication links efficiently, an estimate must be made of the receiver signal strength. Often radio planning engineers have very little, if any, measured signal strength data for specific locations, and so a radio propagation model must be used to evaluate the signal level that is likely to occur for different percentages of the year, at the locations of interest. A critical factor in any such radio propagation model is the variation of radio refractive index with height in the troposphere. Also, the height range of significance is dependent on the path length. Any model must therefore take account of refractive index variations in both time and space. One way this can be done is by investigating the extent to which the cumulative distribution of average refractive index gradient varies as a function of the height interval over which the average is calculated. The paper discusses an analysis that has been carried out at the British Telecom Research Laboratories (BTRL) to investigate the statistics of the average radio refractive index gradient