Simulations of Radar Reflectivity Factors at 94GHz: Ice Crystal Approximation with Oblate Spheroids

This study explores the potential of simulating cloud radar reflectivity factors (RRF) at 94GHz from a combination of cloud particle 2D images from optical array probes and bulk condensed water content, simultaneously measured during the first aircraft field campaign of the High Altitude Ice Crystals (HAIC) / High Ice Water Content (HIWC) international project performed out of Darwin in 2014. Within these simulations, ice crystals are approximated by oblate spheroids without a priori assumptions on mass-size relationships of ice crystals. The method allows calculating time dependent ranges of radar reflectivity factors deduced for given size distributions of hydrometeors, averaged over 5 seconds. Ice hydrometeor size distributions and shapes (flattening parameter for oblate spheroids) are deduced from 2D images, and are subsequently used to constrain the ice particle density (thereby matching simulated and corresponding measured radar reflectivity factors). Finally, uncertainties in oblate spheroid approximations are studied in order to demonstrate some limitations of this method.