In-cloud aircraft icing due to the presence of super cooled liquid water can adversely affect aircraft performance. Aircraft icing has been cited as the cause of both military and general aviation accidents. Presently, general aviation forecasts of in-cloud aircraft icing have low resolution and are fairly inaccurate. Therefore, pilots are left with the options of either contending with the icing conditions or not flying at all. There does not exist a ground base or aircraft system that can detect the cloud parameters required for predicting in-cloud icing potential. In-cloud icing potential is a function of the presence of super cooled liquid water, and to some degree, the range of droplet diameters. Intense icing conditions appear to be associated with clouds that have large super cooled liquid water contents and a drizzle size drop component. Results will be presented on an approach that uses a multi-frequency radar system in conjunction with a neural network to determine both liquid water content and particle size information. Ten thousand cases using drop (cloud, drizzle and rain) spectra associated with stratiform and cumuliform cloud types with and without ice were used to train the neural net. Range profiles of radar back scatter for two hundred cloud cases were use to test the algorithm for both a two and three frequency radar system. The neural network was used to invert the radar back scatter profiles to obtain range resolved cloud liquid water and particle size information. The three-band radar system operating at X, Ka, and W frequencies showed the most skill for predicting both the liquid water content and information on the particle size. A two frequency radar system showed considerable skill in predicting the liquid water content, but was not as successful at predicating particle size information. A multi-frequency airborne radar system would have the potential to detect both liquid water content and particle size information for ranges of several tens of kilometers ahead of the aircraft
The 8th Conference on Aviation, Range, and Aerospace Meteorology