Microphysical Processes of Melting Snowflakes Detected by Two-Wavelength Radar

Part I. Principle of Measurement Based on Model Calculation

Abstract

The possibility for two-wavelength radar to detect the microphysical processes in the melting layer is discussed based on model calculations.
We calculated the characteristics of microwave scattering by precipitation particles based on the non-coalescence and non-breakup model and monodispersed coalescence or breakup model in the melting layer and obtained the vertical profiles of radar reflectivity factor for both 3.21cm wavelength (X-band) and 5.6cm wavelength (C-band). The results of the calculations show a possibility to detect the shift of the size distribution associated with coalescence and/or breakup of melting snowflakes in the upper-half region of the melting layer. The reason can be well understood by considering that the radar sensitivity of the microwave scattering to the change in particle size deviates between the two wavelengths, and that the sensitivity to the change in the other parameters such as fall velocity of particles is equal between the two wavelengths. Therefore the two-wavelength radar measurement is useful to detect the shift of the particle size distribution in the melting layer.