Abstract :
Field-strength recordings on beyond-line-of-sight paths show distinct enhancement during thunderstorm activity. Measurements at 92, 1100 and 3500MHz were carried out during thunderstorm conditions. The increase of field strength at the higher frequency can sometimes be more than 40dB, but it depends on frequency and scattering angle. The increase in field strength is caused by a diverging downdraught of cold air in the thunderstorm area.
