Testing the Consistency of the Boundary Element Method for Computing the Backscattering Properties of Complex Ice Crystals at Multiple Radar Frequencies

The backscattering properties of randomly oriented complex rosette ice aggregates at the radar frequencies of about 9, 35, and 94 GHz are computed using the boundary element method. A Monte Carlo model is used to generate the rosette aggregates, and 65 aggregates are selected from the statistical runs that are within ±30% of a mass-dimension relation that is consistent with the Met Office's cirrus microphysics scheme in its weather and climate models. The area- dimension relationship is shown to be generally consistent with an observed area-size power law. The budding rosettes and rosette aggregates have maximum dimensions between about 10 μm and 1 cm. To test the budding rosette and rosette aggregate model, data from NASA's IMPACTS campaign are used. The IMPACTS data consists of four frontal snowstorm cases that achieved the best co-incident measurements between the in-situ and remote sensing aircraft. We show that the rosette aggregate model predicts the time series of radar reflectivity data generally well for all four cases.