Simulation of EarthCARE spaceborne doppler radar products using ground-based and airborne data: Effects of aliasing and nonuniform beam-filling

This paper describes the expected performance of the Doppler cloud profiling radar being built for the Earth Cloud Aerosols Radiation Explorer (EarthCARE) mission of the Japanese Aerospace Exploration Agency and the European Space Agency. Spaceborne Doppler radar data are simulated starting from high-resolution Doppler measurements provided by ground-based and airborne Doppler radars, ranging from nonconvective to moderately convective scenarios. The method hinges upon spatial and spectral resampling to consider the specificities of the spaceborne configuration. An error analysis of the resulting Doppler product is conducted to address aliasing and nonuniform beam-filling (NUBF) problems. A perturbation analysis is applied to explore the latter problem and allow for a self-standing systematic correction of NUBF using merely the received reflectivity factor and mean Doppler velocities as measured by the instrument. The results of our simulations show that, at a horizontal integration of 1 km, after proper de-aliasing and NUBF correction, the radar will typically yield a velocity accuracy in the order of 1.3 m.s^-1 over intertropical regions where the pulse-repetition frequency (PRF})=6.1 kHz, of 0.8 m.s^-1 where the cloud-profiling radar (CPR) operates at PRF=7 kHz, and, of 0.7 ms^-1 over high latitudes where the CPR of EarthCARE will operate at PRF=7.5 kHz.