PREDICTIONS OF RADIOWAVE ATTENUATIONS DUE TO A MELTING LAYER OF PRECIPITATION

A melting layer model related to the physical constants and meteorolog ical parameters is employed in this investigation. The specific phase shift, together with the specific attenuation, is computed at 1-100 GH z by using the Mie theory. The additional zenith attenuation, which is the difference between zenith attenuation due to the melting layer an d attenuation due to the same thickness of the resulting rain, is comp rehensively studied. The ratio of the difference to rain zenith attenu ation may be over 1 at 1-5 GHz although the difference is much less th an 1 dB. The difference can be over 1 dB at frequencies above 20 GHz. A minimum of the ratio is below 0.05 at frequencies about 40-60 GHz bu t the ratio can become a value of about 0.1 at 100 GHz. The additional attenuation should be taken into account in satellite-earth communica tions and radar remote sensing. The power law parameters of the averag e specific attenuation of the melting layer and rain specific attenuat ion are tabulated for three raindrop size distributions at rain rates of below 25 mm/h. The power law method could be utilized in the additi onal attenuation calculation. It is a good approximation of the Mie th eory results at 1-50 GHz and a useful estimate at 50-100 GHz.