Variability of Gaseous Attenuation at Very Low Elevation Angle Slant Paths; Measurements and Modelling

Gaseous attenuation variability for a 3.2° elevation angle satellite link operating at 20 GHz in the Norwegian Arctic is analyzed and compared with different models. At a very low elevation link like this one, gaseous attenuation reaches high values and has significant temporal variation over short periods of time. 5 months of measured data are compared with a model based on measured ground meteorological data and two different numerical weather prediction (NWP) models. The simplified model based on ground data gives lower values than the measured levels and is unable to model the observed fast variations. Both the NWP model based on predictions and the one based on re-analysis of past data are able to model most of the fast variations. When cloud attenuation is included in the NWP models both show excellent agreement with the measured data, without a clear difference in accuracy between them.