Predicted Effects of Nonuniform Beam Filling on GPM Radar Data

The global precipitation measurement mission (GPM) will carry the first dual-frequency spaceborne radar (DPR) for rainfall observation. We use dual-frequency airborne radar data to simulate observations at GPM DPR resolution and frequencies and to investigate errors due to nonuniform beam filling effects. Errors at Ku-band are similar to those found in previous studies. Errors in the Ka-band path-integrated attenuation and near-surface reflectivity are larger than at Ku-band. Errors in rain-top reflectivity, where attenuation is neglected, are smaller at Ka-band than at Ku-band because the Ka-band Z-R relation is closer to being linear.