Measured and modeled spatial rain rate correlation to improve the prediction method for satellite site diversity

Abstract

Rainfall rate varies both temporarily and spatially. Radio systems, where rain attenuation causes outages, may take advantage of this effect to increase the radio link or satellite link availability using diversity techniques. In the Oslo region with Norwegian Meteorological Institute located at Blindern, there are 24 tipping bucket rain gauges within 50 km radius of the institute where each station has 5 years or more of simultaneous data periods with the station at the institute. The simultaneous data have been used to calculate spatial rain rate correlation and derive a prediction method based on separation distance and orientation with respect to dominating weather direction. Part of joint rain rate distribution was fitted to lognormal to find the measured correlation coefficients. In addition, an analysis of independent radiosonde data suggests that prevailing wind at 700 hPa or 850 hPa altitude (approximately 3000 m or 1500 m above sea level), conditioned thunderstorm index in the range of 15 to 20, may be used to identify the actual rainfall movement or dominant weather direction. Compared with current recommended method by the Radiocommunication Sector of International Telecommunication Union, the new method gives an improved site diversity prediction judged by site selection of minimum 20 GHz attenuation data measured in 2012 from Earth stations located at Nittedal and Kjeller separated by 23 km.

Three-Site Diversity at Ka-Band Satellite Links in Norway: Gain, Fade Duration, and the Impact of Switching Schemes

“…The sites were separated by 23, 29.7 and 50.1 km, and positioned approximately on a straight line in an area where spatial correlation of rain has previously been extensively studied [13].…”

“…The elevation angle towards Ka-Sat is almost identical as well ranging from 21.7 to 22°. The stations are located approximately in line with the main weather (precipitation) direction found by a detailed study of spatial rain rate correlation in the area [13].…”